@article {1783181, title = {Self-organizing behaviors of cardiovascular cells on synthetic nanofiber scaffolds}, journal = {APL Bioengineering}, volume = {7}, number = {4}, year = {2023}, abstract = {In tissues and organs, the extracellular matrix (ECM) helps maintain inter- and intracellular architectures that sustain the structure{\textendash}function relationships defining physiological homeostasis. Combining fiber scaffolds and cells to form engineered tissues is a means of replicating these relationships. Engineered tissues{\textquoteright} fiber scaffolds are designed to mimic the topology and chemical composition of the ECM network. Here, we asked how cells found in the heart compare in their propensity to align their cytoskeleton and self-organize in response to topological cues in fibrous scaffolds. We studied cardiomyocytes, valvular interstitial cells, and vascular endothelial cells as they adapted their inter- and intracellular architectures to the extracellular space. We used focused rotary jet spinning to manufacture aligned fibrous scaffolds to mimic the length scale and three-dimensional (3D) nature of the native ECM in the muscular, valvular, and vascular tissues of the heart. The representative cardiovascular cell types were seeded onto fiber scaffolds and infiltrated the fibrous network. We measured different cell types{\textquoteright} propensity for cytoskeletal alignment in response to fiber scaffolds with differing levels of anisotropy. The results indicated that valvular interstitial cells on moderately anisotropic substrates have a higher propensity for cytoskeletal alignment than cardiomyocytes and vascular endothelial cells. However, all cell types displayed similar levels of alignment on more extreme (isotropic and highly anisotropic) fiber scaffold organizations. These data suggest that in the hierarchy of signals that dictate the spatiotemporal organization of a tissue, geometric cues within the ECM and cellular networks may homogenize behaviors across cell populations and demographics.}, url = {https://pubs.aip.org/aip/apb/article/7/4/046114/2925594/Self-organizing-behaviors-of-cardiovascular-cells}, author = {158. and Michael M. Peters and Jackson K. Brister and Edward M. Tang and Felita W. Zhang and Veronica M. Lucian and Paul D. Trackey and Zachary Bone and John F. Zimmerman and Qianru Jin and F. John Burpo and Kevin Kit Parker} } @article {1767606, title = {Impact response of advance combat helmet pad systems}, journal = {International Journal of Impact Engineering}, volume = {181}, year = {2023}, abstract = {Combat helmets are designed to protect against ballistic threats and fragments of explosive devices. There are numerous types of helmet comfort foams available. However, pad systems have not been evaluated in combat helmets to understand to what extent they mitigate head accelerations. In this work, different pad systems are studied to analyze the ballistic performance of combat helmets using a Hybrid III dummy equipped with longitudinal accelerometers at the head and a neck simulator. The tests are conducted with 9\ mm Full Metal Jacket (FMJ) projectiles according to the performance requirements III-A of the NIJ 0106.01 standard. This experimental methodology allows the evaluation of brain and neck injuries. The thicker bicomponent polyurethane foams and the honeycomb configuration provided the best results in terms of mitigating brain damage due to accelerations applying different criteria (PLA, WSTC, HIC). However, it was concluded that there is no cervical injury or cranial fracture risk for any of the cases studied.}, url = {https://www.sciencedirect.com/science/article/pii/S0734743X23002671}, author = {157. and M. Rodriguez-Millan and I. Rubio and F.J. Burpo and A. Olmedo and J.A. Loya and Parker, K. K. and M.H Migu{\'e}lez,} } @article {1705226, title = {Experimental and Numerical Analyses of Ballistic Resistance Evaluation of Combat Helmet using Hybrid III Headform}, journal = {International Journal of Impact Engineering}, volume = {179}, year = {2023}, abstract = {Combat helmets are the primary system for protecting the head against ballistic impacts. Generally, combat helmets have been evaluated using a ballistic plasticine head surrogate based on international standards. More realistic human head models have recently been introduced to assess combat helmet performance considering biomechanical requirements. In this work, the Hybrid III dummy head and neck has been introduced to evaluate the performance of the combat helmet against the ballistic impact of live ammunition at different impact locations, considering two different thicknesses of the padding system. A numerical model including a helmet and a Hybrid III head and neck, is developed and validated with our experimental data. The results reveal the influence of the location, where the rear impact leads to the highest risk of brain damage. The effect of pad thickness is closely related to the energy absorbed by the helmet, the backface deformation (BFD), the contact force and the acceleration measured on the head.}, url = {https://www.sciencedirect.com/science/article/pii/S0734743X23001641?via\%3Dihub}, author = {156. and M. Rodriguez-Millan and I. Rubio and F.J. Burpo and K.M. Tse and A. Olmedo and J.A. Loya and Parker, K. K. and M.H. Migu{\textasciiacute}elez} } @article {1745446, title = {Spatiotemporal cell junction assembly in human iPSC-CM models of arrhythmogenic cardiomyopathy}, journal = {Stem Cell Reports}, volume = {18}, year = {2023}, pages = {1-16}, abstract = {Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that causes life-threatening arrhythmias and myocardial dysfunction. Pathogenic variants in Plakophilin-2 (PKP2), a desmosome component within specialized cardiac cell junctions, cause the majority of ACM cases. However, the molecular mechanisms by which PKP2 variants induce disease phenotypes remain unclear. Here we built bioengineered platforms using genetically modified human induced pluripotent stem cell-derived cardiomyocytes to model the early spatiotemporal process of cardiomyocyte junction assembly in\ vitro. Heterozygosity for truncating variant PKP2R413X reduced Wnt/β-catenin signaling, impaired myofibrillogenesis, delayed mechanical coupling, and reduced calcium wave velocity in\ engineered tissues. These abnormalities were ameliorated by SB216763, which activated Wnt/β-catenin signaling, improved cytoskeletal\ organization, restored cell junction integrity in cell pairs, and improved calcium wave velocity in engineered tissues.\ Together, these findings highlight the therapeutic potential of modulating Wnt/β-catenin signaling in a human model of ACM.}, url = {https://www.cell.com/stem-cell-reports/fulltext/S2213-6711(23)00267-9$\#$secsectitle0020}, author = {155. and Sean L. Kim and Michael A. Trembley and Keel Yong Lee and Suji Choi and Luke A. MacQueen and John F. Zimmerman and Lousanne H.C. de Wit and Kevin Shani and Douglas E. Henze and Daniel J. Drennan and Shaila A. Saifee and Li Jun Loh and Xujie Liu and Kevin Kit Parker and Pu, William T.} } @article {1732201, title = {Fibre-infused gel scaffolds guide cardiomyocyte alignment in 3-D printed ventricles}, journal = {Nature Materials}, volume = {22}, year = {2023}, pages = {1039 {\textendash} 1046}, abstract = {Hydrogels are attractive materials for tissue engineering, but efforts to date have shown limited ability to produce the microstructural features necessary to promote cellular self-organization into hierarchical three-dimensional (3D) organ models. Here we develop a hydrogel ink containing prefabricated gelatin fibres to print 3D organ-level scaffolds that recapitulate the intra- and intercellular organization of the heart. The addition of prefabricated gelatin fibres to hydrogels enables the tailoring of the ink rheology, allowing for a controlled sol{\textendash}gel transition to achieve precise printing of free-standing 3D structures without additional supporting materials. Shear-induced alignment of fibres during ink extrusion provides microscale geometric cues that promote the self-organization of cultured human cardiomyocytes into anisotropic muscular tissues in vitro. The resulting 3D-printed ventricle in vitro model exhibited biomimetic anisotropic electrophysiological and contractile properties.}, url = {https://www.nature.com/articles/s41563-023-01611-3$\#$citeas}, author = {154. and Suji Choi and Keel Yong Lee and Sean L. Kim and Luke A. MacQueen and Huibin Chang and John F. Zimmerman and Qianru Jin and Michael M. Peters and Herdeline Ann M. Ardo{\~n}a and Xujie Liu and Ann-Caroline Heiler and Rudy Gabardi and Collin Richardson and Pu, William T. and Andreas R. Bausch and Kevin Kit Parker} } @article {1702791, title = {On-demand heart valve manufacturing using focused rotary jet spinning}, journal = {Matter}, volume = {6}, number = {6}, year = {2023}, pages = {1860-1879}, abstract = {Children worldwide suffer from heart valve disease and often require open heart surgeries for valve replacements. Unfortunately, current heart valve replacements do not grow alongside the child, necessitating repeat high-risk surgeries throughout the pediatric patient{\textquoteright}s life. This work introduces FibraValves, heart valve replacements fabricated in minutes that comprise of fibers produced by focused rotary jet spinning. FibraValves are manufactured using biodegradable polymer fibers that allow for the patient{\textquoteright}s cells to attach and remodel the implanted scaffold, eventually building a native valve that can grow and live with the child throughout their life. These valves were tested in\ vitro and deployed in acute in\ vivo studies to evaluate their ability to maintain unidirectional blood flow in the heart. Together, these results suggest the potential translation of FibraValves as future cardiac implants, eliminating the need for repeated valve replacements in children.}, url = {https://www.cell.com/matter/fulltext/S2590-2385(23)00243-6$\#$\%20}, author = {153. and Sarah E. Motta and Michael M. Peters and Christophe O. Chantre and Huibin Chang and Luca Cera and Liu, Qihan and Elizabeth M. Cordoves and Emanuela S. Fioretta and Polina Zaytseva and Nikola Cesarovic and Maximilian Y. Emmert and Simon P. Hoerstrup and Kevin Kit Parker} } @article {1705221, title = {Light-triggered Cardiac Microphysiological Model}, journal = {APL Bioengineering }, volume = {7}, number = {2}, year = {2023}, abstract = {Light is recognized as an accurate and noninvasive tool for stimulating excitable cells. Here, we report on a non-genetic approach based onorganic molecular phototransducers that allows wiring- and electrode-free tissue modulation. As a proof of concept, we show photostimulationof an in vitro cardiac microphysiological model mediated by an amphiphilic azobenzene compound that preferentially dwells in the cell membrane.Exploiting this optical based stimulation technology could be a disruptive approach for highly resolved cardiac tissue stimulation.}, author = {152. and V. Vurro and K. Shani and H. A. M. Ardona and Zimmerman, J. F. and V. Sesti and Lee, K. Y. and Q. Jin and C. Bertarelli and Parker, K. K. and G. Lanzani} } @article {1645963, title = {Recreating the Heart{\textquoteright}s Helical Structure-Function Relationship with Focused Rotary Jet Spinning}, journal = {Science}, volume = {377}, number = {6602}, year = {2022}, pages = {180-185}, abstract = {Helical alignments within the heart{\textquoteright}s musculature have been speculated to be important in achieving physiological pumping efficiencies. Testing this possibility is difficult, however, because it is challenging to reproduce the fine spatial features and complex structures of the heart{\textquoteright}s musculature using current techniques. Here we report focused rotary jet spinning (FRJS), an additive manufacturing approach that enables rapid fabrication of micro/nanofiber scaffolds with programmable alignments in three-dimensional geometries. Seeding these scaffolds with cardiomyocytes enabled the biofabrication of tissue-engineered ventricles, with helically aligned models displaying more uniform deformations, greater apical shortening, and increased ejection fractions compared with circumferential alignments. The ability of FRJS to control fiber arrangements in three dimensions offers a streamlined approach to fabricating tissues and organs, with this work demonstrating how helical architectures contribute to cardiac performance.}, url = {https://www.science.org/doi/10.1126/science.abl6395 }, author = {151. and Huibin Chang and Liu, Qihan and John F. Zimmerman and Keel Yong Lee and Qianru Jin and Michael M. Peters and Michael Rosnach and Suji Choi and Sean L. Kim and Herdeline Ann M. Ardo{\~n}a and Luke A. MacQueen and Christophe O. Chantre and Sarra E. Motta and Elizabeth M. Cordoves and Kevin Kit Parker} } @article {1645430, title = {High-Throughput Coating with Biodegradable Anitmicrobial Pullulan Fibres Extends Shelf Life and Reduces Weight Loss in an Avocado}, journal = {Nature Food}, volume = {3}, year = {2022}, pages = {428-436}, abstract = { Food waste and food safety motivate the need for improved food packaging solutions. However, current films/coatings addressing these issues are often limited by inefficient release dynamics that require large quantities of active ingredients. Here we developed antimicrobial pullulan fibre (APF)-based packaging that is biodegradable and capable of wrapping food substrates, increasing their longevity and enhancing their safety. APFs were spun using a high-throughput system, termed focused rotary jet spinning, with water as the only solvent, allowing the incorporation of naturally derived antimicrobial agents. Using avocados as a representative example, we demonstrate that APF-coated samples had their shelf life extended by inhibited proliferation of natural microflora, and lost less weight than uncoated control samples. This work offers a promising technique to produce scalable, low-cost and environmentally friendly biodegradable antimicrobial packaging systems. }, url = {https://www.nature.com/articles/s43016-022-00523-w}, author = {150. and Huibin Chang and Jie Xu and Luke A. MacQueen and Zeynep Aytac and Michael M. Peters and John F. Zimmerman and Tao Xu and Philip Demokritou and Kevin Kit Parker} } @article {1645429, title = {Cellular and Engineered Organoids for Cardiovascular Models}, journal = {Circulation Research}, volume = {130}, number = {12}, year = {2022}, pages = {1780-1802}, abstract = { An ensemble of in vitro cardiac tissue models has been developed over the past several decades to aid our understanding of complex cardiovascular disorders using a reductionist approach. These approaches often rely on recapitulating single or multiple clinically relevant end points in a dish indicative of the cardiac pathophysiology. The possibility to generate disease-relevant and patient-specific human induced pluripotent stem cells has further leveraged the utility of the cardiac models as screening tools at a large scale. To elucidate biological mechanisms in the cardiac models, it is critical to integrate physiological cues in form of biochemical, biophysical, and electromechanical stimuli to achieve desired tissue-like maturity for a robust phenotyping. Here, we review the latest advances in the directed stem cell differentiation approaches to derive a wide gamut of cardiovascular cell types, to allow customization in cardiac model systems, and to study diseased states in multiple cell types. We also highlight the recent progress in the development of several cardiovascular models, such as cardiac organoids, microtissues, engineered heart tissues, and microphysiological systems. We further expand our discussion on defining the context of use for the selection of currently available cardiac tissue models. Last, we discuss the limitations and challenges with the current state-of-the-art cardiac models and highlight future directions. }, url = {https://www.ahajournals.org/doi/epub/10.1161/CIRCRESAHA.122.320305}, author = {149. and Dilip Thomas and Suji Choi and Christina Alamana and Kevin Kit Parker and Joseph C. Wu} } @article {1645428, title = {Differential Modulation of Endothelial Cytoplasmic Protrusions After Exposure to Graphene-Family Nanomaterials}, journal = {NanoImpact}, volume = {26}, year = {2022}, abstract = { Engineered nanomaterials offer the benefit of having systematically tunable physicochemical characteristics (e.g., size, dimensionality, and surface chemistry) that highly dictate the biological activity of a material. Among the most promising engineered nanomaterials to date are graphene-family nanomaterials (GFNs), which are 2-D nanomaterials (2DNMs) with unique electrical and mechanical properties. Beyond engineering new nanomaterial properties, employing safety-by-design through considering the consequences of cell-material interactions is essential for exploring their applicability in the biomedical realm. In this study, we asked the effect of GFNs on the endothelial barrier function and cellular architecture of vascular endothelial cells. Using micropatterned cell pairs as a reductionist in vitro model of the endothelium, the progression of cytoskeletal reorganization as a function of GFN surface chemistry and time was quantitatively monitored. Here, we show that the surface oxidation of GFNs (graphene, reduced graphene oxide, partially reduced graphene oxide, and graphene oxide) differentially affect the endothelial barrier at multiple scales; from the biochemical pathways that influence the development of cellular protrusions to endothelial barrier integrity. More oxidized GFNs induce higher endothelial permeability and the increased formation of cytoplasmic protrusions such as filopodia. We found that these changes in cytoskeletal organization, along with barrier function, can be potentiated by the effect of GFNs on the Rho/Rho-associated kinase (ROCK) pathway. Specifically, GFNs with higher surface oxidation elicit stronger ROCK2 inhibitory behavior as compared to pristine graphene sheets. Overall, findings from these studies offer a new perspective towards systematically controlling the surface-dependent effects of GFNs on cytoskeletal organization via ROCK2 inhibition, providing insight for implementing safety-by-design principles in GFN manufacturing towards their targeted biomedical applications. }, url = {https://www.sciencedirect.com/science/article/abs/pii/S2452074822000234?via\%3Dihub}, author = {148. and Herdeline Ann M. Ardo{\~n}a and John F. Zimmerman and Kevin Shani and Su Hwan Kim and Feyisayo Eweje and Dimitrios Bitounis and Dorsa Parviz and Evan Casalino and Michael Strano and Philip Demokritou and Kevin Kit Parker} } @article {1633650, title = {An autonomously swimming biohybrid fish designed with human cardiac biophysics}, journal = {Science}, volume = {375}, number = {6581}, year = {2022}, pages = {639{\textendash}647}, abstract = {Biohybrid systems have been developed to better understand the design principles and coordination mechanisms of biological systems. We consider whether two functional regulatory features of the heart{\textemdash}mechanoelectrical signaling and automaticity{\textemdash}could be transferred to a synthetic analog of another fluid transport system: a swimming fish. By leveraging cardiac mechanoelectrical signaling, we recreated reciprocal contraction and relaxation in a muscular bilayer construct where each contraction occurs automatically as a response to the stretching of an antagonistic muscle pair. Further, to entrain this closed-loop actuation cycle, we engineered an electrically autonomous pacing node, which enhanced spontaneous contraction. The biohybrid fish equipped with intrinsic control strategies demonstrated self-sustained body{\textendash}caudal fin swimming, highlighting the role of feedback mechanisms in muscular pumps such as the heart and muscles.}, url = {https://doi.org/10.1126/science.abh0474}, author = {147 - and Lee, K. Y. and Park, S.-J. and Matthews, D. G. and Kim, S. L. and Marquez, C. A. and Zimmerman, J. F. and Ardo{\~n}a, H. A. and Kleber, A. G. and Lauder, G. and Parker, K. K.} } @article {1626072, title = {An Extracellular Matrix-Liposome Composite, a Novel Extracellular Matrix Delivery System for Accelerated Tissue Regeneration}, journal = {Advanced Healthcare Materials}, year = {2022}, abstract = {The unfolded states of fibronectin (FN) subsequently induce the formation of an extracellular matrix (ECM) fibrillar network, which is necessary to generate new substitutive tissues. Here, the authors demonstrate that negatively charged small unilamellar vesicles (SUVs) qualify as candidates for FN delivery due to their remarkable effects on the autonomous binding and unfolding of FN, which leads to increased tissue regeneration. In vitro experiments revealed that the FN-SUV complex remarkably increased the attachment, differentiation, and migration of fibroblasts. The potential utilization of this complex in vivo to treat inflammatory colon diseases is also described based on results obtained for ameliorated conditions in rats with ulcerative colitis (UC) that had been treated with the FN-SUV complex. Their findings provide a new ECM-delivery platform for ECM-based therapeutic applications and suggest that properly designed SUVs may be an unprecedented FN-delivery system that is highly effective in treating UC and inflammatory bowel diseases.}, url = {https://doi.org/10.1002/adhm.202101599}, author = {146 - and Lee KY and Nguyen HT and Setiawati A and Nam S-J and Kim M and Ko I-G and Jung WH and Parker KK and Kim C-J and Shin KW} } @article {1626071, title = {Prednisolone Rescues Duchenne Muscular Dystrophy Phenotypes in Human Pluripotent Stem Cell{\textendash}Derived Skeletal Muscle in Vitro}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {28}, year = {2021}, pages = {1-12}, abstract = {Duchenne muscular dystrophy (DMD) is a devastating genetic disease leading to degeneration of skeletal muscles and premature death. How dystrophin absence leads to muscle wasting remains unclear. Here, we describe an optimized protocol to differentiate human induced pluripotent stem cells (iPSC) to a late myogenic stage. This allows us to recapitulate classical DMD phenotypes (mislocalization of proteins of the dystrophin-associated glycoprotein complex, increased fusion, myofiber branching, force contraction defects, and calcium hyperactivation) in isogenic DMD-mutant iPSC lines in vitro. Treatment of the myogenic cultures with prednisolone (the standard of care for DMD) can dramatically rescue force contraction, fusion, and branching defects in DMD iPSC lines. This argues that prednisolone acts directly on myofibers, challenging the largely prevalent view that its beneficial effects are caused by antiinflammatory properties. Our work introduces a human in vitro model to study the onset of DMD pathology and test novel therapeutic approaches.}, url = {https://doi.org/10.1073/pnas.2022960118}, author = {145 - and Ziad AT and Zimmerman JF and Rao J and Sieiro D and McNamara HM and Cherrier T and Rodriguez-delaRosa A and Hick-Colin A and Bousson F and Fugier-Schmucker C and Marchianoi F and Habermanni B and Chala J and Nesmith AP and Gapon and Svetlana and Wagner E and Gupta VA and Bassel-Dubyk R and Olsonk EN and Cohen AE and Parker KK} } @article {1626070, title = {Building Biomimetic Potency Tests for Islet Transplantation}, journal = {Diabetes}, volume = {70}, number = {2}, year = {2021}, pages = {347-363}, abstract = {Diabetes is a disease of insulin insufficiency, requiring many to rely on exogenous insulin with constant monitoring to avoid a fatal outcome. Islet transplantation is a recent therapy that can provide insulin independence, but the procedure is still limited by both the availability of human islets and reliable tests to assess their function. While stem cell technologies are poised to fill the shortage of transplantable cells, better methods are still needed for predicting transplantation outcome. To ensure islet quality, we propose that the next generation of islet potency tests should be biomimetic systems that match glucose stimulation dynamics and cell microenvironmental preferences and rapidly assess conditional and continuous insulin secretion with minimal manual handing. Here, we review the current approaches for islet potency testing and outline technologies and methods that can be used to arrive at a more predictive potency test that tracks islet secretory capacity in a relevant context. With the development of potency tests that can report on islet secretion dynamics in a context relevant to their intended function, islet transplantation can expand into a more widely accessible and reliable treatment option for individuals with diabetes.}, url = {https://doi.org/10.2337/db20-0297}, author = {144 - and Glieberman AL and Pope BD and Melton DA and Parker KK} } @article {1625787, title = {Nanofiber assembly by rotary jet spinning}, journal = {Publisher}, volume = {10}, number = {6}, year = {2021}, pages = {2257-2261}, abstract = {High-voltage electrical fields and low production rate limit electrospinning, the electrical charging of polymer liquids, as a means of nanofiber fabrication. Here, we show a facile method of fabrication of aligned three-dimensional nanofiber structures by utilizing high-speed, rotating polymer solution jets to extrude fibers. Termed rotary jet-spinning, fiber morphology, diameter, and web porosity can be controlled by varying nozzle geometry, rotation speed, and polymer solution properties. We demonstrate the utility of this technique for tissue engineering by building anisotropic arrays of biodegradable polymer fibers and seeding the constructs with neonatal rat ventricular cardiomyocytes. The myocytes used the aligned fibers to orient their contractile cytoskeleton and to self-organize into a beating, multicellular tissue that mimics the laminar, anisotropic architecture of the heart muscle. This technique may prove advantageous for building uniaxially aligned nanofiber structures for polymers which are not amenable to fabrication by electrospinning.}, url = {https://doi.org/10.1021/nl101355x}, author = {143 - and Badrossamay MR and McIlwee HA and Goss JA and Parker KK} } @article {1626052, title = {Some Data Is Hard To Get-Some Data You Have to Be Hard to Get}, journal = {Matter}, volume = {3}, number = {3}, year = {2020}, pages = {623{\textendash}627}, abstract = {My second tour of duty in the Global War on Terror took me, an Army reservist, from my research and teaching at Harvard to the mountainous valleys of eastern Afghanistan. My job on this tour, working for the Center for Army Lessons Learned, was to try to understand how we were trying to rid the battlefield of improvised explosive devices, or IEDs, which were causing most of the Coalition casualties. A field-grade officer with no troops under my command, I roamed my area of operation attached to tactical units to collect data. One such group was Route Clearance Patrol 13 (RCP13), an amalgam of combat engineers, explosive specialists, and specialized teams, clearing roads of IEDs (Figure 1). On these missions, I sat strapped into its Buffalo, a motorized beast whose extraordinary size and robotic arm capabilities were designed to directly engage the explosive devices in lieu of dispatching someone to check it out themselves.}, url = {https://doi.org/10.1016/j.matt.2020.08.017}, author = {142 - and Parker, K. K.} } @article {1626069, title = {Welcome to Biophysics Reviews, a big tent for the biophysics community}, journal = {Biophysics Reviews}, volume = {1}, number = {1}, year = {2020}, pages = {010401}, abstract = {It is our pleasure to welcome you to the first issue of Biophysics Reviews (BPR), a new journal from AIP Publishing covering the diverse field of biophysics. The journal expands on the tradition of excellence set by Applied Physics Reviews (APR) by publishing high impact, cutting edge research and reviews that are valuable for both emerging and experienced researchers.}, url = {https://doi.org/10.1063/5.0036408}, author = {141 - and Parker KK and Longobardi L and Sulicz A} } @article {1626073, title = {Endothelial extracellular vesicles contain protective proteins and rescue ischemia-reperfusion injury in a human heart-on-chip}, journal = {Science Translational Medicine}, volume = {12}, number = {565}, year = {2020}, pages = {eaax8005}, abstract = {Extracellular vesicles, small membrane-bound particles released from cells, have been shown to have cardioprotective effects. Here, Yadid et al. analyzed the proteins contained in vesicles released from endothelial cells under normoxia and hypoxia and investigated cardioprotective effects on cardiac tissues in vitro. Using a human heart-on-chip composed of cardiomyocytes, the authors showed that endothelial cell{\textendash}derived vesicles supported metabolic function, tissue contraction, and viability during ischemia-reperfusion injury. This study helps to elucidate the mechanism by which vesicles are cardioprotective in human tissue.}, author = {140 - and Yadid M and Lind JU and Ardo{\~n}a HAM and Sheehy SP and Dickinson LE and Eweje F and Bastings MCB and Pope B and O{\textquoteright}Connor BB and Straubhaar JR and Budnik B, Kleb} } @article {1626064, title = {Development of biodegradable and antimicrobial electrospun zein fibers for food packaging}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {8}, number = {40}, year = {2020}, pages = {15354-15365}, abstract = {There is an urgent need to develop biodegradable and nontoxic materials from biopolymers and nature-derived antimicrobials to enhance food safety and quality. In this study, electrospinning was used as a one-step, scalable, green synthesis approach to engineer antimicrobial fibers from zein using nontoxic organic solvents and a cocktail of nature-derived antimicrobials which are all FDA-classified Generally Recognized as Safe (GRAS) for food use. Morphological and physicochemical properties of fibers, as well as the dissolution kinetics of antimicrobials were assessed along with their antimicrobial efficacy using state of the art analytical and microbiological methods. A cocktail of nature-derived antimicrobials was developed and included thyme oil, citric acid, and nisin. Its ability to inactivate a broad-spectrum of with food-related pathogens was demonstrated. Morphological characterization of the electrospun antimicrobial fibers revealed bead-free fibers with a small average diameter of 165 nm, whereas physicochemical characterization showed high surface area-to-volume ratio (specific surface area:21.91 m2/g) and presence of antimicrobial analytes in the fibers. The antimicrobials exhibited initial rapid release from the fibers in 2 h into various food simulants. Furthermore, the antimicrobial fibers effectively reduced E. coli and L. innocua populations by \~{}5 logs for after 24 h and 1 h of exposure, respectively. More importantly, due to the small diameter and high surface area-to-volume ratio of the fibers, only miniscule quantities of fiber mass and antimicrobials per surface area (2.50 mg/cm2 of fibers) are needed for pathogen inactivation. The scalability of this fiber synthesis process was also demonstrated using a multineedle injector with production yield up to 1 g/h. This study shows the potential of using nature-derived biopolymers and antimicrobials to synthesize fibers for sustainable food packaging materials.}, url = {https://doi.org/10.1021/acssuschemeng.0c05917}, author = {139 - and Aytac Z and Huang R and Vaze N and Xu T and Eitzer BD and Krol W and MacQueen LA and Chang H and Bousfield DW and Chan-Park MB and Ng KW and Parker KK and White JC and Demokritou P} } @article {1626068, title = {Fattening chips: hypertrophy, feeding, and fasting of human white adipocytes in vitro}, journal = {Lab on a Chip}, number = {22}, year = {2020}, abstract = {Adipose is a distributed organ that performs vital endocrine and energy homeostatic functions. Hypertrophy of white adipocytes is a primary mode of both adaptive and maladaptive weight gain in animals and predicts metabolic syndrome independent of obesity. Due to the failure of conventional culture to recapitulate adipocyte hypertrophy, technology for production of adult-size adipocytes would enable applications such as in vitro testing of weight loss therapeutics. To model adaptive adipocyte hypertrophy in vitro, we designed and built fat-on-a-chip using fiber networks inspired by extracellular matrix in adipose tissue. Fiber networks extended the lifespan of differentiated adipocytes, enabling growth to adult sizes. By micropatterning preadipocytes in a native cytoarchitecture and by adjusting cell-to-cell spacing, rates of hypertrophy were controlled independent of culture time or differentiation efficiency. In vitro hypertrophy followed a nonlinear, nonexponential growth model similar to human development and elicited transcriptomic changes that increased overall similarity with primary tissue. Cells on the chip responded to simulated meals and starvation, which potentiated some adipocyte endocrine and metabolic functions. To test the utility of the platform for therapeutic development, transcriptional network analysis was performed, and retinoic acid receptors were identified as candidate drug targets. Regulation by retinoid signaling was suggested further by pharmacological modulation, where activation accelerated and inhibition slowed hypertrophy. Altogether, this work presents technology for mature adipocyte engineering, addresses the regulation of cell growth, and informs broader applications for synthetic adipose in pharmaceutical development, regenerative medicine, and cellular agriculture.}, url = {https://doi.org/10.1039/D0LC00508H}, author = {138 - and Pope BD and Warren CR and Dahl MO and Pizza CV and Henze DE and Sinatra NR and Gonzalez GM and Chang H and Liu Q and Gleiberman AL and Ferrier JP and Cowan CA and Parker KK} } @article {1626063, title = {Next-generation tissue-engineered heart valves with repair, remodelling and regeneration capacity}, journal = {Nature Reviews Cardiology}, volume = {18}, year = {2020}, pages = {92{\textendash}116}, abstract = {Valvular heart disease is a major cause of morbidity and mortality worldwide. Surgical valve repair or replacement has been the standard of care for patients with valvular heart disease for many decades, but transcatheter heart valve therapy has revolutionized the field in the past 15 years. However, despite the tremendous technical evolution of transcatheter heart valves, to date, the clinically available heart valve prostheses for surgical and transcatheter replacement have considerable limitations. The design of next-generation tissue-engineered heart valves (TEHVs) with repair, remodelling and regenerative capacity can address these limitations, and TEHVs could become a promising therapeutic alternative for patients with valvular disease. In this Review, we present a comprehensive overview of current clinically adopted heart valve replacement options, with a focus on transcatheter prostheses. We discuss the various concepts of heart valve tissue engineering underlying the design of next-generation TEHVs, focusing on off-the-shelf technologies. We also summarize the latest preclinical and clinical evidence for the use of these TEHVs and describe the current scientific, regulatory and clinical challenges associated with the safe and broad clinical translation of this technology.}, url = {https://doi.org/10.1038/s41569-020-0422-8}, author = {137 - and Fioretta ES and Motta SE and Lintas Valentina and Loerakker S and Parker KK and Baaijens FPT and Falk V and Hoerstrup SP and Emmert MY} } @article {1626053, title = {para-Aramid Fiber Sheets for Simultaneous Mechanical and Thermal Protection in Extreme Environments}, journal = {Matter}, volume = {3}, number = {3}, year = {2020}, pages = {742-758}, abstract = {First responders and military personnel working under extreme conditions require protection against multiple hazards, including thermal and ballistic protection. However, traditional materials lack multiple types of protection in a single protective layer. By controlling the chemical and structural makeup of high-performance fibers across multiple length scales, this work demonstrates a multifunctional sheet capable of providing simultaneous thermal and ballistic protection. These sheets are composed of long, continuous fibers to resist a mechanical load and large pores to limit heat transfer. By combining these structure-function properties, these fibers overcome traditional trade-offs, providing mechanical performance equivalent to commercially available ballistic fibers while providing 20-fold insulation capability. Overcoming previous limitations, this approach enables simultaneous thermal and mechanical protection for astronauts, bomb disposal experts, and warfighters.}, url = {https://doi.org/10.1016/j.matt.2020.06.001}, author = {136 - and Gonzalez GM and Ward J and Song J and Swana K and Fossey SA and Palmer JL and Zhang FW and Lucian VM and Cera L and Zimmerman JF and Burpo FJ and Parker KK} } @article {1626050, title = {A bioinspired and hierarchically structured shape-memory material}, journal = {Nature Materials}, volume = {20}, year = {2020}, pages = {242{\textendash}249}, abstract = {Shape-memory polymeric materials lack long-range molecular order that enables more controlled and efficient actuation mechanisms. Here, we develop a hierarchical structured keratin-based system that has long-range molecular order and shape-memory properties in response to hydration. We explore the metastable reconfiguration of the keratin secondary structure, the transition from α-helix to β-sheet, as an actuation mechanism to design a high-strength shape-memory material that is biocompatible and processable through fibre spinning and three-dimensional (3D) printing. We extract keratin protofibrils from animal hair and subject them to shear stress to induce their self-organization into a nematic phase, which recapitulates the native hierarchical organization of the protein. This self-assembly process can be tuned to create materials with desired anisotropic structuring and responsiveness. Our combination of bottom-up assembly and top-down manufacturing allows for the scalable fabrication of strong and hierarchically structured shape-memory fibres and 3D-printed scaffolds with potential applications in bioengineering and smart textiles.}, url = {https://doi.org/10.1038/s41563-020-0789-2}, author = {135 - and Cera L and Gonzalez GM and Liu Q and Choi S and Chantre CO and Lee J and Gabardi R and Choi MC and Shin K and Parker KK} } @article {1626051, title = {Proteomic and Metabolomic Characterization of Human Neurovascular Unit Cells in Response to Methamphetamine}, journal = {Advanced Biosystems}, volume = {4}, number = {9}, year = {2020}, pages = {e1900230}, abstract = {The functional state of the neurovascular unit (NVU), composed of the blood{\textendash}brain barrier and the perivasculature that forms a dynamic interface between the blood and the central nervous system (CNS), plays a central role in the control of brain homeostasis and is strongly affected by CNS drugs. Human primary brain microvascular endothelium, astrocyte, pericyte, and neural cell cultures are often used to study NVU barrier functions as well as drug transport and efficacy; however, the proteomic and metabolomic responses of these different cell types are not well characterized. Culturing each cell type separately, using deep coverage proteomic analysis and characterization of the secreted metabolome, as well as measurements of mitochondrial activity, the responses of these cells under baseline conditions and when exposed to the NVU-impairing stimulant methamphetamine (Meth) are analyzed. These studies define the previously unknown metabolic and proteomic profiles of human brain pericytes and lead to improved characterization of the phenotype of each of the NVU cell types as well as cell-specific metabolic and proteomic responses to Meth.}, url = {https://doi.org/10.1002/adbi.201900230}, author = {134 - and Herland A and Maoz BM and Fitzgerald EA and Grevesse T and Vidoudez C and Sheehy SP and Budnik N and Dauth S and Mannix R and Budnik B and Parker KK and Ingber DE} } @article {1626048, title = {The role of extracellular matrix in normal and pathological pregnancy: Future applications of microphysiological systems in reproductive medicine}, journal = {Experimental Biology and Medicine}, volume = {245}, number = {13}, year = {2020}, pages = {1163-1174}, abstract = {Extracellular matrix in the womb regulates the initiation, progression, and completion of a healthy pregnancy. The composition and physical properties of extracellular matrix in the uterus and at the maternal-fetal interface are remodeled at each gestational stage, while maladaptive matrix remodeling results in obstetric disease. As in vitro models of uterine and placental tissues, including micro-and milli-scale versions of these organs on chips, are developed to overcome the inherent limitations of studying human development in vivo, we can isolate the influence of cellular and extracellular components in healthy and pathological pregnancies. By understanding and recreating key aspects of the extracellular microenvironment at the maternal-fetal interface, we can engineer microphysiological systems to improve assisted reproduction, obstetric disease treatment, and prenatal drug safety.}, url = {https://doi.org/10.1177/1535370220938741}, author = {133 - and O{\textquoteright}Connor BB and Pope B and Peters MM and Ris-Stalpers C and Parker KK} } @article {1626065, title = {Biomimetic and estrogenic fibers promote tissue repair in mice and human skin via estrogen receptor β}, journal = {Biomaterials}, volume = {255}, year = {2020}, pages = {120149}, abstract = {The dynamic changes in estrogen levels throughout aging and during the menstrual cycle influence wound healing. Elevated estrogen levels during the pre-ovulation phase accelerate tissue repair, whereas reduced estrogen levels in post-menopausal women lead to slow healing. Although previous reports have shown that estrogen may potentiate healing by triggering the estrogen receptor (ER)-β signaling pathway, its binding to ER-α has been associated with severe collateral effects and has therefore limited its use as a therapeutic agent. To this end, soy phytoestrogens, which preferentially bind to the ER-β, are currently being explored as a safer therapeutic alternative to estrogen. However, the development and evaluation of phytoestrogen-based materials as local ER-β modulators remains largely unexplored. Here, we engineered biomimetic and estrogenic nanofiber wound dressings built from soy protein isolate (SPI) and hyaluronic acid (HA) using immersion rotary jet spinning. These engineered scaffolds were shown to successfully recapitulate the native dermal architecture, while delivering an ER-β-triggering phytoestrogen (genistein). When tested in ovariectomized mouse and ex vivo human skin tissues, HA/SPI scaffolds outperformed controls (no treatment or HA only scaffolds) towards promoting cutaneous tissue repair. These improved healing outcomes were prevented when the ER-β pathway was genetically or chemically inhibited. Our findings suggest that estrogenic fibrous scaffolds facilitate skin repair by ER-β activation.}, url = {https://doi.org/10.1016/j.biomaterials.2020.120149}, author = {132 - and Ahn S and Chantre CO and Ardo{\~n}a HAM and Gonzalez GM and Campbell PH and Parker KK} } @article {1626049, title = {Continuous Formation of Ultrathin, Strong Collagen Sheets with Tunable Anisotropy and Compaction}, journal = {ACS Biomaterials Science \& Engineering}, volume = {6}, number = {7}, year = {2020}, pages = {4236-4246}, abstract = {The multiscale organization of protein-based fibrillar materials is a hallmark of many organs, but the recapitulation of hierarchal structures down to fibrillar scales, which is a requirement for withstanding physiological loading forces, has been challenging. We present a microfluidic strategy for the continuous, large-scale formation of strong, handleable, free-standing, multicentimeter-wide collagen sheets of unprecedented thinness through the application of hydrodynamic focusing with the simultaneous imposition of strain. Sheets as thin as 1.9 μm displayed tensile strengths of 0.5{\textendash}2.7 MPa, Young{\textquoteright}s moduli of 3{\textendash}36 MPa, and modulated the diffusion of molecules as a function of collagen nanoscale structure. Smooth muscle cells cultured on engineered sheets oriented in the direction of aligned collagen fibrils and generated coordinated vasomotor responses. The described biofabrication approach enables rapid formation of ultrathin collagen sheets that withstand physiologically relevant loads for applications in tissue engineering and regenerative medicine, as well as in organ-on-chip and biohybrid devices.}, url = {https://doi.org/10.1021/acsbiomaterials.0c00321}, author = {131 - and Malladi S and Miranda-Nieves D and Leng L and Grainger SJ and Tarabanis C and Nesmith AP and Kosaraju R and Haller CA and Parker KK and Chaikof EL and Guenther A} } @article {1626047, title = {Human brain microvascular endothelial cell pairs model tissue-level blood{\textendash}brain barrier function}, journal = {Integrative Biology}, volume = {2}, number = {3}, year = {2020}, pages = {64-79}, abstract = {The blood-brain barrier plays a critical role in delivering oxygen and nutrients to the brain while preventing the transport of neurotoxins. Predicting the ability of potential therapeutics and neurotoxicants to modulate brain barrier function remains a challenge due to limited spatial resolution and geometric constraints offered by existing in vitro models. Using soft lithography to control the shape of microvascular tissues, we predicted blood-brain barrier permeability states based on structural changes in human brain endothelial cells. We quantified morphological differences in nuclear, junction, and cytoskeletal proteins that influence, or indicate, barrier permeability. We established a correlation between brain endothelial cell pair structure and permeability by treating cell pairs and tissues with known cytoskeleton-modulating agents, including a Rho activator, a Rho inhibitor, and a cyclic adenosine monophosphate analog. Using this approach, we found that high-permeability cell pairs showed nuclear elongation, loss of junction proteins, and increased actin stress fiber formation, which were indicative of increased contractility. We measured traction forces generated by high- and low-permeability pairs, finding that higher stress at the intercellular junction contributes to barrier leakiness. We further tested the applicability of this platform to predict modulations in brain endothelial permeability by exposing cell pairs to engineered nanomaterials, including gold, silver-silica, and cerium oxide nanoparticles, thereby uncovering new insights into the mechanism of nanoparticle-mediated barrier disruption. Overall, we confirm the utility of this platform to assess the multiscale impact of pharmacological agents or environmental toxicants on blood-brain barrier integrity.}, url = {https://doi.org/10.1093/intbio/zyaa005}, author = {130 - and O{\textquoteright}Connor BB and Grevesse T and Zimmerman JF and Ardo{\~n}a HAM and Jimenez JA and Bitounis D and Demokritou P and Parker KK} } @article {1626044, title = {Inhibition of mTOR Signaling Enhances Maturation of Cardiomyocytes Derived from Human Induced Pluripotent Stem Cells via p53-Induced Quiescence}, journal = {Circulation}, volume = {141}, number = {4}, year = {2020}, pages = {285-300}, abstract = {Background: Current differentiation protocols to produce cardiomyocytes from human induced pluripotent stem cells (iPSCs) are capable of generating highly pure cardiomyocyte populations as determined by expression of cardiac troponin T. However, these cardiomyocytes remain immature, more closely resembling the fetal state, with a lower maximum contractile force, slower upstroke velocity, and immature mitochondrial function compared with adult cardiomyocytes. Immaturity of iPSC-derived cardiomyocytes may be a significant barrier to clinical translation of cardiomyocyte cell therapies for heart disease. During development, cardiomyocytes undergo a shift from a proliferative state in the fetus to a more mature but quiescent state after birth. The mechanistic target of rapamycin (mTOR)-signaling pathway plays a key role in nutrient sensing and growth. We hypothesized that transient inhibition of the mTOR-signaling pathway could lead cardiomyocytes to a quiescent state and enhance cardiomyocyte maturation.}, url = {https://doi.org/10.1161/circulationaha.119.044205}, author = {129 - and Garbern JC and Helman A and Sereda R and Sarikhani M and Ahmed A and Escalante GO and Ogurlu R and Kim SL and Zimmerman JF and Cho A and MacQueen LM and Bezzerides VJ and Parker KK and Melton DA and Lee RT} } @article {1626046, title = {Quantitative prediction of human pharmacokinetic responses to drugs via fluidically coupled vascularized organ chips}, journal = {Nature Biomedical Engineering}, volume = {4}, number = {4}, year = {2020}, pages = {421-436}, abstract = {Analyses of drug pharmacokinetics (PKs) and pharmacodynamics (PDs) performed in animals are often not predictive of drug PKs and PDs in humans, and in vitro PK and PD modelling does not provide quantitative PK parameters. Here, we show that physiological PK modelling of first-pass drug absorption, metabolism and excretion in humans{\textemdash}using computationally scaled data from multiple fluidically linked two-channel organ chips{\textemdash}predicts PK parameters for orally administered nicotine (using gut, liver and kidney chips) and for intravenously injected cisplatin (using coupled bone marrow, liver and kidney chips). The chips are linked through sequential robotic liquid transfers of a common blood substitute by their endothelium-lined channels (as reported by Novak et al. in an associated Article) and share an arteriovenous fluid-mixing reservoir. We also show that predictions of cisplatin PDs match previously reported patient data. The quantitative in-vitro-to-in-vivo translation of PK and PD parameters and the prediction of drug absorption, distribution, metabolism, excretion and toxicity through fluidically coupled organ chips may improve the design of drug-administration regimens for phase-I clinical trials.}, url = {https://dx.doi.org/10.1038\%2Fs41551-019-0498-9}, author = {128 - and Herland A and Maoz BM and Das D and Somayaji MR and Prantil-Baun R and Novak R and Cronce M and Huffstater T and Jeanty SSF and Ingram M and Chalkiadaki A and Chou DB and Marquez S and Delahanty A and Jalili-Firoozinezhad S and Sontheimer-Phelps A and Swenor B and Levy O and Parker KK and Przekwas A and Ingber DE} } @article {1626045, title = {Robotic fluidic coupling and interrogation of multiple vascularied organ chips}, journal = {Nature Biomedical Engineering}, volume = {4}, number = {4}, year = {2020}, pages = {407-420}, abstract = {Organ chips can recapitulate organ-level (patho)physiology, yet pharmacokinetic and pharmacodynamic analyses require multi-organ systems linked by vascular perfusion. Here, we describe an {\textquoteleft}interrogator{\textquoteright} that employs liquid-handling robotics, custom software and an integrated mobile microscope for the automated culture, perfusion, medium addition, fluidic linking, sample collection and in situ microscopy imaging of up to ten organ chips inside a standard tissue-culture incubator. The robotic interrogator maintained the viability and organ-specific functions of eight vascularized, two-channel organ chips (intestine, liver, kidney, heart, lung, skin, blood{\textendash}brain barrier and brain) for 3 weeks in culture when intermittently fluidically coupled via a common blood substitute through their reservoirs of medium and endothelium-lined vascular channels. We used the robotic interrogator and a physiological multicompartmental reduced-order model of the experimental system to quantitatively predict the distribution of an inulin tracer perfused through the multi-organ human-body-on-chips. The automated culture system enables the imaging of cells in the organ chips and the repeated sampling of both the vascular and interstitial compartments without compromising fluidic coupling.}, url = {https://doi.org/10.1038/s41551-019-0497-x}, author = {127 - and Novak R and Ingram M and Marquez S and Das D and Delahanty A and Herland A and Maoz BM and Jeanty SSF and Somayaji MR and Burt M and Calamari E and Chalkiadaki A and Cho A and Choe Y and Chou DB and Cronce M and Dauth S and Divic T and Fernandez-Alcon J and Ferrante T and Ferrier J and Fitzgerald EA and Fleming R and Jalili-Firoozinezhad S and Grevesse T and Goss JA and Hamkins-Indik T and Henry O and Hinojosa C and Huffstater T and Jang KJ and Kujala V and Leng L and Mannix R and Milton Y and Nawroth J and Nestor BA and Ng CF and O{\textquoteright}Connor B and Park TE and Sanchez H and Sliz J and Sontheimer-Phelps A and Swenor B and Thompson G and Touloumes GJ and Tranchemontagne Z and Wen N and Yadid M and Bahinski A and Hamilton GA and Levner D and Levy O and Przekwas A and Prantil-Baun R and Parker KK and Ingber DE} } @article {1626037, title = {Mapping 2D-and 3D-distributions of metal/metal oxide nanoparticles within cleared human ex vivo skin tissues}, journal = {Nanoimpact}, volume = {13}, number = {17}, year = {2020}, pages = {100208}, abstract = {An increasing number of commercial skincare products are being manufactured with engineered nanomaterials (ENMs), prompting a need to fully understand how ENMs interact with the dermal barrier as a major biodistribution entry route. Although animal studies show that certain nanomaterials can cross the skin barrier, physiological differences between human and animal skin, such as the lack of sweat glands, limit the translational validity of these results. Current optical microscopy methods have limited capabilities to visualize ENMs within human skin tissues due to the high amount of background light scattering caused by the dense, ubiquitous extracellular matrix (ECM) of the skin. Here, we hypothesized that organic solvent-based tissue clearing ("immunolabeling-enabled three-dimensional imaging of solvent-cleared organs", or "iDISCO") would reduce background light scattering from the extracellular matrix of the skin to sufficiently improve imaging contrast for both 2D mapping of unlabeled metal oxide ENMs and 3D mapping of fluorescent nanoparticles. We successfully mapped the 2D distribution of label-free TiO2 and ZnO nanoparticles in cleared skin sections using correlated signals from darkfield, brightfield, and confocal microscopy, as well as micro-spectroscopy. Specifically, hyperspectral microscopy and Raman spectroscopy confirmed the identity of label-free ENMs which we mapped within human skin sections. We also measured the 3D distribution of fluorescently labeled Ag nanoparticles in cleared skin biopsies with wounded epidermal layers using light sheet fluorescence microscopy. Overall, this study explores a novel strategy for quantitatively mapping ENM distributions in cleared ex vivo human skin tissue models using multiple imaging modalities. By improving the imaging contrast, we present label-free 2D ENM tracking and 3D ENM mapping as promising capabilities for nanotoxicology investigations.}, url = {https://doi.org/10.1016/j.impact.2020.100208}, author = {126 - and Touloumes GJ and Ardo{\~n}a HAM and Casalino EK and Zimmerman JF and Chantre CO and Bitounis D and Demokritou P and Parker KK} } @article {1626033, title = {Alfalfa Nanofibers for Dermal Wound Healing}, journal = {American Chemical Society Applied Materials \& Interfaces}, volume = {11}, number = {37}, year = {2019}, pages = {33535-33547}, abstract = {Engineering bioscaffolds for improved cutaneous tissue regeneration remains a healthcare challenge because of the increasing number of patients suffering from acute and chronic wounds. To help address this problem, we propose to utilize alfalfa, an ancient medicinal plant that contains antibacterial/oxygenating chlorophylls and bioactive phytoestrogens, as a building block for regenerative wound dressings. Alfalfa carries genistein, which is a major phytoestrogen known to accelerate skin repair. The scaffolds presented herein were built from composite alfalfa and polycaprolactone (PCL) nanofibers with hydrophilic surface and mechanical stiffness that recapitulate the physiological microenvironments of skin. This composite scaffold was engineered to have aligned nanofibrous architecture to accelerate directional cell migration. As a result, alfalfa-based composite nanofibers were found to enhance the cellular proliferation of dermal fibroblasts and epidermal keratinocytes in vitro. Finally, these nanofibers exhibited reproducible regenerative functionality by promoting re-epithelialization and granulation tissue formation in both mouse and human skin, without requiring additional proteins, growth factors, or cells. Overall, these findings demonstrate the potential of alfalfa-based nanofibers as a regenerative platform toward accelerating cutaneous tissue repair.}, url = {https://doi.org/10.1021/acsami.9b07626}, author = {125 - and Ahn S and Ardo{\~n}a HAM and Campbell PH and Gonzalez GM and Parker KK} } @article {1626002, title = {Designer Assays for Your Sick, Subdivided Heart}, journal = {Cell}, volume = {176}, number = {4}, year = {2019}, pages = {684-685}, abstract = {Using induced pluripotent stem cells and microelectromechanical device technology Zhao et al. have developed {\textquoteright}organs on chips{\textquoteright} representing the different chambers of the heart and used them to replicate healthy and diseased tissues in vitro. These systems offer investigators and the pharmaceutical industry a new tool in testing the safety and efficacy of new medicinal therapeutics.}, url = {https://doi.org/10.1016/j.cell.2019.01.028}, author = {124 - and Parker KK} } @article {1626005, title = {Engineering biomimetic and instructive materials for wound healing and regeneration.}, journal = {Current Opinion in Biomedical Engineering}, volume = {10}, year = {2019}, pages = {97-106}, abstract = {Development of biomimetic and instructive materials is emerging as a promising approach for redirecting fibrotic wound healing into a regenerative process. In nature, complete tissue regeneration can transpire in certain organ substructures, during embryogenesis and, remarkably, in some organisms in which whole limbs can regrow. These regenerative phenomena were observed to possess specific extracellular matrices, as well as stem cell niches and regulatory signaling pathways, that likely act as spatiotemporal organizers of these preferred outcomes. Biomimetic materials are now improving on the limitations of existing wound care treatments because they are being designed to stimulate these spatiotemporal cues, thus supporting regeneration within host tissues. A variety of novel materials have already emerged and demonstrated promise both in preclinical studies and in patients. This review discusses the recent advances in understanding these biomimetic and instructive properties and their integration into wound care scaffolds.}, url = {https://doi.org/10.1016/j.cobme.2019.04.004}, author = {123 - and Chantre CO and Hoerstrup SP and Parker KK} } @article {1626004, title = {Inkjet-Printed Carbon Nanotubes for Fabricating a Spoof Fingerprint on Paper}, journal = {American Chemical Society Omega}, volume = {4}, number = {5}, year = {2019}, pages = {8626-31}, abstract = {A spoof fingerprint was fabricated on paper and applied for a spoofing attack to unlock a smartphone on which a capacitive array of sensors had been embedded with a fingerprint recognition algorithm. Using an inkjet printer with an ink made of carbon nanotubes (CNTs), we printed a spoof fingerprint having an electrical and geometric pattern of ridges and furrows comparable to that of the real fingerprint. With this printed spoof fingerprint, we were able to unlock a smartphone successfully; this was due to the good quality of the printed CNT material, which provided electrical conductivities and structural patterns similar to those of the real fingerprint. This result confirms that inkjet-printing CNTs to fabricate a spoof fingerprint on paper is an easy, simple spoofing route from the real fingerprint and suggests a new method for outputting the physical ridges and furrows on a two-dimensional plane.}, url = {https://doi.org/10.1021/acsomega.9b00936}, author = {122 - and Soum V and Park S and Brilian AI and Kim Y and Ryu MY and Brazell T and Burpo FJ and Parker KK and Kwon OS and Shin K} } @article {1626006, title = {Insights Into the Pathogenesis of Catecholaminergic Polymorphic Ventricular Tachycardia From Engineered Human Heart Tissue}, journal = {Circulation}, volume = {140}, number = {5}, year = {2019}, pages = {390-404}, abstract = {Modeling of human arrhythmias with induced pluripotent stem cell{\textendash}derived cardiomyocytes has focused on single-cell phenotypes. However, arrhythmias are the emergent properties of cells assembled into tissues, and the impact of inherited arrhythmia mutations on tissue-level properties of human heart tissue has not been reported.}, url = {https://doi.org/10.1161/CIRCULATIONAHA.119.039711}, author = {121 - and Park SJ and Zhang D and Qi Y and Y, Li and Lee KY and Bezzerides VJ and Yang P and Xia S and Kim SL and Liu X and Lu F and Pasqualini FS and Campbell PH and Geva J and Roberts A and Kleber AG and Abrams DJ and Pu WT and Parker KK} } @article {1626035, title = {Muscle tissue engineering in fibrous gelatin: implications for meat analogs}, journal = {npj Science of Food}, volume = {3}, number = {20}, year = {2019}, abstract = {Bioprocessing applications that derive meat products from animal cell cultures require food-safe culture substrates that support volumetric expansion and maturation of adherent muscle cells. Here we demonstrate scalable production of microfibrous gelatin that supports cultured adherent muscle cells derived from cow and rabbit. As gelatin is a natural component of meat, resulting from collagen denaturation during processing and cooking, our extruded gelatin microfibers recapitulated structural and biochemical features of natural muscle tissues. Using immersion rotary jet spinning, a dry-jet wet-spinning process, we produced gelatin fibers at high rates (~ 100 g/h, dry weight) and, depending on process conditions, we tuned fiber diameters between ~ 1.3 {\textpm} 0.1 μm (mean {\textpm} SEM) and 8.7 {\textpm} 1.4 μm (mean {\textpm} SEM), which are comparable to natural collagen fibers. To inhibit fiber degradation during cell culture, we crosslinked them either chemically or by co-spinning gelatin with a microbial crosslinking enzyme. To produce meat analogs, we cultured bovine aortic smooth muscle cells and rabbit skeletal muscle myoblasts in gelatin fiber scaffolds, then used immunohistochemical staining to verify that both cell types attached to gelatin fibers and proliferated in scaffold volumes. Short-length gelatin fibers promoted cell aggregation, whereas long fibers promoted aligned muscle tissue formation. Histology, scanning electron microscopy, and mechanical testing demonstrated that cultured muscle lacked the mature contractile architecture observed in natural muscle but recapitulated some of the structural and mechanical features measured in meat products.}, url = {https://doi.org/10.1038/s41538-019-0054-8}, author = {120 - and MacQueen LM and Alver CG and Chantre CO and Ahn S and Cera L and Gonzalez GM and O{\textquoteright}Connor BB and Drennan DJ and Peters MM and Motta SE and Zimmerman JF and Parker KK} } @article {1626036, title = {Porous Biomimetic Hyaluronic Acid and Extracellular Matrix Protein Nanofiber Scaffolds for Accelerated Cutaneous Tissue Repair}, journal = {American Chemical Society Applied Materials \& Interfaces}, volume = {11}, number = {49}, year = {2019}, pages = {45498-45510}, abstract = {Recent reports suggest the utility of extracellular matrix (ECM) molecules as raw components in scaffolding of engineered materials. However, rapid and tunable manufacturing of ECM molecules into fibrous structures remains poorly developed. Here we report on an immersion rotary jet-spinning (iRJS) method to show high-throughput manufacturing (up to \~{}1 g/min) of hyaluronic acid (HA) and other ECM fiber scaffolds using different spinning conditions and postprocessing modifications. This system allowed control over a variety of scaffold material properties, which enabled the fabrication of highly porous (70{\textendash}95\%) and water-absorbent (swelling ratio \~{}2000{\textendash}6000\%) HA scaffolds with soft-tissue mimetic mechanical properties (\~{}0.5{\textendash}1.5 kPa). Tuning these scaffolds{\textquoteright} properties enabled the identification of porosity (\~{}95\%) as a key facilitator for rapid and in-depth cellular ingress in vitro. We then demonstrated that porous HA scaffolds accelerated granulation tissue formation, neovascularization, and reepithelialization in vivo, altogether potentiating faster wound closure and tissue repair. Collectively, this scalable and versatile manufacturing approach enabled the fabrication of tunable ECM-mimetic nanofiber scaffolds that may provide an ideal first building block for the design of all-in-one healing materials.}, url = {https://doi.org/10.1021/acsami.9b17322}, author = {119 - and Chantre CO and Gonzalez GM and Ahn S and Cera L and Campbell PH and Hoerstrup SP and Parker KK} } @article {1626034, title = {Quantifying the effects of engineered nanomaterials on endothelial cell architecture and vascular barrier integrity using a cell pair model}, journal = {Nanoscale}, volume = {11}, number = {38}, year = {2019}, pages = {17878-17893}, abstract = {Engineered nanomaterials (ENMs) are increasingly used in consumer products due to their unique physicochemical properties, but the specific hazards they pose to the structural and functional integrity of endothelial barriers remain elusive. When assessing the effects of ENMs on vascular barrier function, endothelial cell monolayers are commonly used as in vitro models. Monolayer models, however, do not offer a granular understanding of how the structure-function relationships between endothelial cells and tissues are disrupted due to ENM exposure. To address this issue, we developed a micropatterned endothelial cell pair model to quantitatively evaluate the effects of 10 ENMs (8 metal/metal oxides and 2 organic ENMs) on multiple cellular parameters and determine how these parameters correlate to changes in vascular barrier function. This minimalistic approach showed concerted changes in endothelial cell morphology, intercellular junction formation, and cytoskeletal organization due to ENM exposure, which were then quantified and compared to unexposed pairs using a "similarity scoring" method. Using the cell pair model, this study revealed dose-dependent changes in actin organization and adherens junction formation following exposure to representative ENMs (Ag, TiO2 and cellulose nanocrystals), which exhibited trends that correlate with changes in tissue permeability measured using an endothelial monolayer assay. Together, these results demonstrate that we can quantitatively evaluate changes in endothelial architecture emergent from nucleo-cytoskeletal network remodeling using micropatterned cell pairs. The endothelial pair model therefore presents potential applicability as a standardized assay for systematically screening ENMs and other test agents for their cellular-level structural effects on vascular barriers.}, url = {https://doi.org/10.1039/c9nr04981a}, author = {118 - and Eweje F and Ardo{\~n}a HAM and Zimmerman JF and O{\textquoteright}Connor BB and Ahn S and Grevesse T and Rivera KN and Demokritou P and Parker KK} } @article {1626003, title = {Scatter Enhanced Phase Contrast Microscopy for Discriminating Mechanisms of Active Nanoparticle Transport in Living Cells}, journal = {Nanoletters}, volume = {19}, number = {2}, year = {2019}, pages = {793-804}, abstract = {Understanding the uptake and transport dynamics of engineered nanomaterials (ENMs) by mammalian cells is an important step in designing next-generation drug delivery systems. However, to track these materials and their cellular interactions, current studies often depend on surface-bound fluorescent labels, which have the potential to alter native cellular recognition events. As a result, there is still a need to develop methods capable of monitoring ENM-cell interactions independent of surface modification. Addressing these concerns, here we show how scatter enhanced phase contrast (SEPC) microscopy can be extended to work as a generalized label-free approach for monitoring nanoparticle uptake and transport dynamics. To determine which materials can be studied using SEPC, we turn to Lorenz{\textendash}Mie theory, which predicts that individual particles down to \~{}35 nm can be observed. We confirm this experimentally, demonstrating that SEPC works for a variety of metal and metal oxides, including Au, Ag, TiO2, CeO2, Al2O3, and Fe2O3 nanoparticles. We then demonstrate that SEPC microscopy can be used in a quantitative, time-dependent fashion to discriminate between distinct modes of active cellular transport, including intracellular transport and membrane-assisted transport. Finally, we combine this technique with microcontact printing to normalize transport dynamics across multiple cells, allowing for a careful study of ensemble TiO2 nanoparticle uptake. This revealed three distinct regions of particle transport across the cell, indicating that membrane dynamics play an important role in regulating particle flow. By avoiding fluorescent labels, SEPC allows for a rational exploration of the surface properties of nanomaterials in their native state and their role in endocytosis and cellular transport.}, url = {https://doi.org/10.1021/acs.nanolett.8b03903}, author = {117 - and Zimmerman JF and Ardo{\~n}a HAM and Pyrgiotakis G and Dong J and Moudgil B and Demokritou P and Parker KK} } @article {1626008, title = {Synchronized Stimulation and Continuous Insulin Sensing in a Microfluidic Human Islet on a Chip Designed for Scalable Manufacturing}, journal = {Lab on a Chip}, volume = {19}, number = {18}, year = {2019}, pages = {2993-3010}, abstract = {Pancreatic β cell function is compromised in diabetes and is typically assessed by measuring insulin secretion during glucose stimulation. Traditionally, measurement of glucose-stimulated insulin secretion involves manual liquid handling, heterogeneous stimulus delivery, and enzyme-linked immunosorbent assays that require large numbers of islets and processing time. Though microfluidic devices have been developed to address some of these limitations, traditional methods for islet testing remain the most common due to the learning curve for adopting microfluidic devices and the incompatibility of most device materials with large-scale manufacturing. We designed and built a thermoplastic, microfluidic-based Islet on a Chip compatible with commercial fabrication methods, that automates islet loading, stimulation, and insulin sensing. Inspired by the perfusion of native islets by designated arterioles and capillaries, the chip delivers synchronized glucose pulses to islets positioned in parallel channels. By flowing suspensions of human cadaveric islets onto the chip, we confirmed automatic capture of islets. Fluorescent glucose tracking demonstrated that stimulus delivery was synchronized within a two-minute window independent of the presence or size of captured islets. Insulin secretion was continuously sensed by an automated, on-chip immunoassay and quantified by fluorescence anisotropy. By integrating scalable manufacturing materials, on-line, continuous insulin measurement, and precise spatiotemporal stimulation into an easy-to-use design, the Islet on a Chip should accelerate efforts to study and develop effective treatments for diabetes.}, url = {https://doi.org/10.1039/C9LC00253G}, author = {116 - and Glieberman AL and Pope BD and Zimmerman JF and Liu Q and Ferrier JP and Kenty JHR and Schrell AM and Mukhitov N and Shores KL and Tepole AB and Melton DA and Roper MG and Parker KK} } @article {1626007, title = {Ultragentle Manipulatoin of Delicate Structures Using a Soft Robotic Gripper}, journal = {Science Robotics}, volume = {4}, number = {33}, year = {2019}, pages = {eaax5425}, abstract = {Here, we present ultragentle soft robotic actuators capable of grasping delicate specimens of gelatinous marine life. Although state-of-the-art soft robotic manipulators have demonstrated gentle gripping of brittle animals (e.g., corals) and echinoderms (e.g., sea cucumbers) in the deep sea, they are unable to nondestructively grasp more fragile soft-bodied organisms, such as jellyfish. Through an exploration of design parameters and laboratory testing of individual actuators, we confirmed that our nanofiber-reinforced soft actuators apply sufficiently low contact pressure to ensure minimal harm to typical jellyfish species. We then built a gripping device using several actuators and evaluated its underwater grasping performance in the laboratory. By assessing the gripper{\textquoteright}s region of acquisition and robustness to external forces, we gained insight into the necessary precision and speed with which grasping maneuvers must be performed to achieve successful collection of samples. Last, we demonstrated successful manipulation of three live jellyfish species in an aquarium setting using a hand-held prototype gripper. Overall, our ultragentle gripper demonstrates an improvement in gentle sample collection compared with existing deep-sea sampling devices. Extensions of this technology may improve a variety of in situ characterization techniques used to study the ecological and genetic features of deep-sea organisms}, url = {https://doi.org/10.1126/scirobotics.aax5425}, author = {115 - and Sinatra NR and Teeple CB and Vogt DM and Parker KK and Gruber DG and Wood RJ} } @article {1625991, title = {Automated fabrication of photopatterned gelatin hydrogels for organ-on-chips applications}, journal = {Biofabrication}, volume = {10}, number = {2}, year = {2018}, pages = {25004}, abstract = {Organ-on-chip platforms aim to improve preclinical models for organ-level responses to novel drug compounds. Heart-on-a-chip assays in particular require tissue engineering techniques that rely on labor-intensive photolithographic fabrication or resolution-limited 3D printing of micropatterned substrates, which limits turnover and flexibility of prototyping. We present a rapid and automated method for large scale on-demand micropatterning of gelatin hydrogels for organ-on-chip applications using a novel biocompatible laser-etching approach. Fast and automated micropatterning is achieved via photosensitization of gelatin using riboflavin-5{\textquoteright}phosphate followed by UV laser-mediated photoablation of the gel surface in user-defined patterns only limited by the resolution of the 15 μm wide laser focal point. Using this photopatterning approach, we generated microscale surface groove and pillar structures with feature dimensions on the order of 10-30 μm. The standard deviation of feature height was 0.3 μm, demonstrating robustness and reproducibility. Importantly, the UV-patterning process is non-destructive and does not alter gelatin micromechanical properties. Furthermore, as a quality control step, UV-patterned heart chip substrates were seeded with rat or human cardiac myocytes, and we verified that the resulting cardiac tissues achieved structural organization, contractile function, and long-term viability comparable to manually patterned gelatin substrates. Start-to-finish, UV-patterning shortened the time required to design and manufacture micropatterned gelatin substrates for heart-on-chip applications by up to 60\% compared to traditional lithography-based approaches, providing an important technological advance enroute to automated and continuous manufacturing of organ-on-chips.}, url = {https://doi.org/10.1088/1758-5090/aa96de}, author = {114 - and Janna C Nawroth and Lisa L Scudder and Ryan T Halvorson and Jason Tresback and John P Ferrier Jr and Sean P Sheehy and Alex Cho and Suraj Kannan and Ilona Sunyovszki and Josue A Goss and Patrick H Campbell and Parker KK} } @article {1625992, title = {Formation of Multi-Component Extracellular Matrix Protein Fibers}, journal = {Scientific Reports}, volume = {8}, number = {1}, year = {2018}, pages = {1913}, abstract = {The extracellular matrix (ECM) consists of polymerized protein monomers that form a unique fibrous network providing stability and structural support to surrounding cells. We harnessed the fibrillogenesis mechanisms of naturally occurring ECM proteins to produce artificial fibers with a heterogeneous protein makeup. Using ECM proteins as fibril building blocks, we created uniquely structured multi-component ECM fibers. Sequential incubation of fibronectin (FN) and laminin (LAM) resulted in self-assembly into locally stacked fibers. In contrast, simultaneous incubation of FN with LAM or collagen (COL) produced molecularly stacked multi-component fibers because both proteins share a similar assembly mechanism or possess binding domains specific to each other. Sequential incubation of COL on FN fibers resulted in fibers with sandwiched layers because COL molecules bind to the external surface of FN fibers. By choosing proteins for incubation according to the interplay of their fibrillogenesis mechanisms and their binding domains (exposed when they unfold), we were able to create ECM protein fibers that have never before been observed.}, url = {https://doi.org/10.1038/s41598-018-20371-8}, author = {113 - and Seungkuk Ahn and Keel Yong Lee and Kwanwoo Shin and Parker KK} } @article {1625999, title = {A linked organ-on-chip model of the human neurovascular unit reveals the metabolic coupling of endothelial and neuronal cells}, journal = {Nature Biotechnology}, volume = {36}, number = {9}, year = {2018}, pages = {865-874}, abstract = {The neurovascular unit (NVU) regulates metabolic homeostasis as well as drug pharmacokinetics and pharmacodynamics in the central nervous system. Metabolic fluxes and conversions over the NVU rely on interactions between brain microvascular endothelium, perivascular pericytes, astrocytes and neurons, making it difficult to identify the contributions of each cell type. Here we model the human NVU using microfluidic organ chips, allowing analysis of the roles of individual cell types in NVU functions. Three coupled chips model influx across the blood{\textendash}brain barrier (BBB), the brain parenchymal compartment and efflux across the BBB. We used this linked system to mimic the effect of intravascular administration of the psychoactive drug methamphetamine and to identify previously unknown metabolic coupling between the BBB and neurons. Thus, the NVU system offers an in vitro approach for probing transport, efficacy, mechanism of action and toxicity of neuroactive drugs.}, url = {https://doi.org/10.1038/nbt.4226}, author = {112 - and Maoz BM and Herland A and Fitzgerald EA and Grevesse T and Vidoudez C and Pacheco AR and Sheehy SP and Park TE and Dauth S and Mannix R and Budnik N and Shores K and Cho A and Nawroth JC and Segr{\`e} D and Budnik B and Ingber DE and Parker KK} } @article {1625998, title = {Mussel-Inspired 3D Fiber Scaffolds for Heart-on-a-Chip Toxicity Studies of Engineered Nanomaterials}, journal = {Publisher}, volume = {410}, number = {24}, year = {2018}, pages = {6141-6154}, abstract = {Due to the unique physicochemical properties exhibited by materials with nanoscale dimensions, there is currently a continuous increase in the number of engineered nanomaterials (ENMs) used in consumer goods. However, several reports associate ENM exposure to negative health outcomes such as cardiovascular diseases. Therefore, understanding the pathological consequences of ENM exposure represents an important challenge, requiring model systems that can provide mechanistic insights across different levels of ENM-based toxicity. To achieve this, we developed a mussel-inspired 3D microphysiological system (MPS) to measure cardiac contractility in the presence of ENMs. While multiple cardiac MPS have been reported as alternatives to in vivo testing, most systems only partially recapitulate the native extracellular matrix (ECM) structure. Here, we show how adhesive and aligned polydopamine (PDA)/polycaprolactone (PCL) nanofiber can be used to emulate the 3D native ECM environment of the myocardium. Such nanofiber scaffolds can support the formation of anisotropic and contractile muscular tissues. By integrating these fibers in a cardiac MPS, we assessed the effects of TiO2 and Ag nanoparticles on the contractile function of cardiac tissues. We found that these ENMs decrease the contractile function of cardiac tissues through structural damage to tissue architecture. Furthermore, the MPS with embedded sensors herein presents a way to non-invasively monitor the effects of ENM on cardiac tissue contractility at different time points. These results demonstrate the utility of our MPS as an analytical platform for understanding the functional impacts of ENMs while providing a biomimetic microenvironment to in vitro cardiac tissue samples.}, url = {https://doi.org/10.1007/s00216-018-1106-7}, author = {111 - and Ahn S and Ardo{\~n}a HAM and Lind JU and Eweje F and Kim SL and Gonzalez GM and Liu Q and Zimmerman JF and Pyrgiotakis G and Zhang Z and Beltran-Huarac J and Carpinone P and Moudgil BM and Demokritou P and Parker KK} } @article {1625997, title = {Nanofiber-reinforced soft fluidic micro-actuators}, journal = {Journal of Micromechanics and Microengineering}, volume = {28}, number = {8}, year = {2018}, pages = {84002}, abstract = {Soft pneumatic actuators are promising candidates for micro-manipulation and delicate gripping due to their wide range of motion and ease of fabrication. While existing elastomer-based devices have attracted attention due to their compliant structures, there is a need for materials that combine flexibility, controllable actuation, and robustness. This paper bridges this capability gap by introducing a novel fabrication strategy for nanofiber-reinforced soft micro-actuators. The design and manufacturing of composite PDMS/nanofiber actuators using soft lithography and rotary jet spinning is described. We examine the impact of lamina design and fiber orientation on actuator curvature, mechanical properties, and pressurization range. Composite actuators displayed a 25.8\% higher maximum pressure than pure PDMS devices. Further, the best nanofiber-reinforced laminates tested were 2.3 times tougher than the control PDMS material while maintaining comparable elongation. Finally, bending and bending-twisting are demonstrated using pristine and laser-patterned nanofiber sheets, respectively.}, url = {https://ui.adsabs.harvard.edu/link_gateway/2018JMiMi..28h4002S/doi:10.1088/1361-6439/aab373}, author = {110 - and Sinatra NR and Ranzani T and Vlassak JJ and Parker KK and Wood RJ} } @article {1625996, title = {Photosynthetic Artificial Organelles Sustain and Control ATP-Dependent Reactions in a Protocellular System}, journal = {Nature Biotechnology}, volume = {36}, number = {6}, year = {2018}, pages = {530-535.}, abstract = {Inside cells, complex metabolic reactions are distributed across the modular compartments of organelles1,2. Reactions in organelles have been recapitulated in vitro by reconstituting functional protein machineries into membrane systems3,4,5. However, maintaining and controlling these reactions is challenging. Here we designed, built, and tested a switchable, light-harvesting organelle that provides both a sustainable energy source and a means of directing intravesicular reactions. An ATP (ATP) synthase and two photoconverters (plant-derived photosystem II and bacteria-derived proteorhodopsin) enable ATP synthesis. Independent optical activation of the two photoconverters allows dynamic control of ATP synthesis: red light facilitates and green light impedes ATP synthesis. We encapsulated the photosynthetic organelles in a giant vesicle to form a protocellular system and demonstrated optical control of two ATP-dependent reactions, carbon fixation and actin polymerization, with the latter altering outer vesicle morphology. Switchable photosynthetic organelles may enable the development of biomimetic vesicle systems with regulatory networks that exhibit homeostasis and complex cellular behaviors.}, url = {https://doi.org/10.1038/nbt.4140}, author = {109 - and Lee KY and Park S-J and Lee KA and Kim S-H and Kim H and Meroz Y and Mahadevan L and Jung K-H and Ahn TK and Parker KK} } @article {1625995, title = {Production-scale fibronectin nanofibers promote wound closure and tissue repair in a dermal mouse model}, journal = {Biomaterials}, volume = {166}, number = {1}, year = {2018}, pages = {96-108}, abstract = {Wounds in the fetus can heal without scarring. Consequently, biomaterials that attempt to recapitulate the biophysical and biochemical properties of fetal skin have emerged as promising pro-regenerative strategies. The extracellular matrix (ECM) protein fibronectin (Fn) in particular is believed to play a crucial role in directing this regenerative phenotype. Accordingly, Fn has been implicated in numerous wound healing studies, yet remains untested in its fibrillar conformation as found in fetal skin. Here, we show that high extensional (\~{}1.2 {\texttimes}105 s-1) and shear (\~{}3 {\texttimes}105 s-1) strain rates in rotary jet spinning (RJS) can drive high throughput Fn fibrillogenesis (\~{}10 mL/min), thus producing nanofiber scaffolds that are used to effectively enhance wound healing. When tested on a full-thickness wound mouse model, Fn nanofiber dressings not only accelerated wound closure, but also significantly improved tissue restoration, recovering dermal and epidermal structures as well as skin appendages and adipose tissue. Together, these results suggest that bioprotein nanofiber fabrication via RJS could set a new paradigm for enhancing wound healing and may thus find use in a variety of regenerative medicine applications.}, url = {https://doi.org/10.1016/j.biomaterials.2018.03.006}, author = {108 - and Chantre CO and Campbell PH and Golecki HM and Buganza AT and Capulli AK and Deravi LF and Dauth S and Sheehy SP and Paten JA and Gledhill K and Doucet YS and Abaci HE and Ahn S and Pope BD and Ruberti JW and Hoerstrup SP and Christiano AM and Parker KK} } @article {1625994, title = {Soy Protein/Cellulose Nanofiber Scaffolds Mimicking Skin Extracellular Matrix for Enhanced Wound Healing}, journal = {Advanced Healthcare Materials}, volume = {7}, number = {9}, year = {2018}, pages = {e1701175}, abstract = {Historically, soy protein and extracts have been used extensively in foods due to their high protein and mineral content. More recently, soy protein has received attention for a variety of its potential health benefits, including enhanced skin regeneration. It has been reported that soy protein possesses bioactive molecules similar to extracellular matrix (ECM) proteins and estrogen. In wound healing, oral and topical soy has been heralded as a safe and cost-effective alternative to animal protein and endogenous estrogen. However, engineering soy protein-based fibrous dressings, while recapitulating ECM microenvironment and maintaining a moist environment, remains a challenge. Here, the development of an entirely plant-based nanofibrous dressing comprised of cellulose acetate (CA) and soy protein hydrolysate (SPH) using rotary jet spinning is described. The spun nanofibers successfully mimic physicochemical properties of the native skin ECM and exhibit a high water retaining capability. In vitro, CA/SPH nanofibers promote fibroblast proliferation, migration, infiltration, and integrin β1 expression. In vivo, CA/SPH scaffolds accelerate re-epithelialization and epidermal thinning as well as reduce scar formation and collagen anisotropy in a similar fashion to other fibrous scaffolds, but without the use of animal proteins or synthetic polymers. These results affirm the potential of CA/SPH nanofibers as a novel wound dressing.}, url = {https://doi.org/10.1002/adhm.201701175}, author = {107 - and Ahn S and Chantre CO and Gannon AR and Lind JU and Campbell PH and Grevesse T and O{\textquoteright}Connor BB and Parker KK} } @article {1626001, title = {A tissue-engineered scale model of the heart ventricle}, journal = {Nature Biomedical Engineering}, volume = {2}, number = {12}, year = {2018}, pages = {930-941}, abstract = {Laboratory studies of the heart use cell and tissue cultures to dissect heart function yet rely on animal models to measure pressure and volume dynamics. Here, we report tissue-engineered scale models of the human left ventricle, made of nanofibrous scaffolds that promote native-like anisotropic myocardial tissue genesis and chamber-level contractile function. Incorporating neonatal rat ventricular myocytes or cardiomyocytes derived from human induced pluripotent stem cells, the tissue-engineered ventricles have a diastolic chamber volume of ~500 {\textmu}l (comparable to that of the native rat ventricle and approximately 1/250 the size of the human ventricle), and ejection fractions and contractile work 50{\textendash}250 times smaller and 104{\textendash}108 times smaller than the corresponding values for rodent and human ventricles, respectively. We also measured tissue coverage and alignment, calcium-transient propagation and pressure{\textendash}volume loops in the presence or absence of test compounds. Moreover, we describe an instrumented bioreactor with ventricular-assist capabilities, and provide a proof-of-concept disease model of structural arrhythmia. The model ventricles can be evaluated with the same assays used in animal models and in clinical settings.}, url = {https://doi.org/10.1038/s41551-018-0271-5}, author = {106 - and MacQueen LA and Sheehy SP and Chantre CO and Zimmerman JF and Pasqualini FS and Liu X and Goss JA and Campbell PH and Gonzalez GM and Park SJ and Capulli AK and Ferrier JP and Kosar TF and Mahadevan L and Pu WT and Parker KK} } @article {1625993, title = {Traction force microscopy of engineered cardiac tissues}, journal = {PLOS One}, volume = {13}, number = {3}, year = {2018}, pages = {e0194706}, abstract = {Cardiac tissue development and pathology have been shown to depend sensitively on microenvironmental mechanical factors, such as extracellular matrix stiffness, in both in vivo and in vitro systems. We present a novel quantitative approach to assess cardiac structure and function by extending the classical traction force microscopy technique to tissue-level preparations. Using this system, we investigated the relationship between contractile proficiency and metabolism in neonate rat ventricular myocytes (NRVM) cultured on gels with stiffness mimicking soft immature (1 kPa), normal healthy (13 kPa), and stiff diseased (90 kPa) cardiac microenvironments. We found that tissues engineered on the softest gels generated the least amount of stress and had the smallest work output. Conversely, cardiomyocytes in tissues engineered on healthy- and disease-mimicking gels generated significantly higher stresses, with the maximal contractile work measured in NRVM engineered on gels of normal stiffness. Interestingly, although tissues on soft gels exhibited poor stress generation and work production, their basal metabolic respiration rate was significantly more elevated than in other groups, suggesting a highly ineffective coupling between energy production and contractile work output. Our novel platform can thus be utilized to quantitatively assess the mechanotransduction pathways that initiate tissue-level structural and functional remodeling in response to substrate stiffness.}, url = {https://doi.org/10.1371/journal.pone.0194706}, author = {105 - and Pasqualini FS and Agarwal A and O{\textquoteright}Connor BB and Liu Q and Sheehy SP and Parker KK} } @article {1626000, title = {A viscoelastic beam theory of polymer jets with application to rotary jet spinning}, journal = {Extreme Mechanics Letters}, volume = {25}, year = {2018}, pages = {7-44}, abstract = {Complex deformation of a polymer jet appears in many manufacturing processes, such as 3D printing, electrospinning, blow spinning, and rotary jet spinning. In these applications, a polymer melt or solution is first extruded through an orifice and forms a jet. The polymer jet is then dynamically deformed until the polymer solidifies. The final product is strongly affected by the deformation of the polymer jet. And the deformation is strongly affected by the viscoelasticity of the polymer. Here we develop a beam theory to incorporate both the nonlinear viscoelasticity and the bending/twisting stiffness of a polymer jet. As a demonstration, we study the formation of a polymer fiber under strong centrifugal force, a fiber manufacturing process known as rotary jet spinning.}, url = {https://doi.org/10.1016/j.eml.2018.10.005}, author = {104 - and Liu Q and Parker KK} } @article {1625989, title = {Biohybrid actuators for robotics: A review of devices actuated by living cells}, journal = {Science}, volume = {2}, number = {12}, year = {2017}, pages = {eaaq0495}, abstract = {Actuation is essential for artificial machines to interact with their surrounding environment and to accomplish the functions for which they are designed. Over the past few decades, there has been considerable progress in developing new actuation technologies. However, controlled motion still represents a considerable bottleneck for many applications and hampers the development of advanced robots, especially at small length scales. Nature has solved this problem using molecular motors that, through living cells, are assembled into multiscale ensembles with integrated control systems. These systems can scale force production from piconewtons up to kilonewtons. By leveraging the performance of living cells and tissues and directly interfacing them with artificial components, it should be possible to exploit the intricacy and metabolic efficiency of biological actuation within artificial machines. We provide a survey of important advances in this biohybrid actuation paradigm.}, url = {https://doi.org/10.1126/scirobotics.aaq0495}, author = {103 - and Ricotti L and Trimmer B and Feinberg AW and Raman R and Parker KK and Bashir R and Sitti M and Martel S and Dario P and Menciassi A} } @article {1625959, title = {Cardiac microphysiological devices with flexible thin-film sensors for higher-throughput drug screening}, journal = {Lab Chip}, volume = {17}, number = {21}, year = {2017}, pages = {3692-3703}, abstract = {Microphysiological systems and organs-on-chips promise to accelerate biomedical and pharmaceutical research by providing accurate in vitro replicas of human tissue. Aside from addressing the physiological accuracy of the model tissues, there is a pressing need for improving the throughput of these platforms. To do so, scalable data acquisition strategies must be introduced. To this end, we here present an instrumented 24-well plate platform for higher-throughput studies of engineered human stem cell-derived cardiac muscle tissues that recapitulate the laminar structure of the native ventricle. In each well of the platform, an embedded flexible strain gauge provides continuous and non-invasive readout of the contractile stress and beat rate of an engineered cardiac tissue. The sensors are based on micro-cracked titanium{\textendash}gold thin films, which ensure that the sensors are highly compliant and robust. We demonstrate the value of the platform for toxicology and drug-testing purposes by performing 12 complete dose{\textendash}response studies of cardiac and cardiotoxic drugs. Additionally, we showcase the ability to couple the cardiac tissues with endothelial barriers. In these studies, which mimic the passage of drugs through the blood vessels to the musculature of the heart, we regulate the temporal onset of cardiac drug responses by modulating endothelial barrier permeability in vitro.}, url = {https://doi.org/10.1039/C7LC00740J}, author = {102 - and Johan U. Lind and Moran Yadid and Ian Perkins and Blakely B. O{\textquoteright}Connor and Feyisayo Eweje and Christophe O. Chantre and Matthew A. Hemphill and Hongyan Yuan and Patrick H. Campbell and Joost J. Vlassak and Parker KK} } @article {1625958, title = {Comparative analysis of poly-glycolic acid-based hybrid polymer starter matrices for in vitro tissue engineering}, journal = {Colloids and Surfaces B: Biointerfaces}, volume = {1}, number = {158}, year = {2017}, pages = {203-212}, abstract = {Biodegradable scaffold matrixes form the basis of any in vitro tissue engineering approach by acting as a temporary matrix for cell proliferation and extracellular matrix deposition until the scaffold is replaced by neo-tissue. In this context several synthetic polymers have been investigated, however a concise systematic comparative analyses is missing. Therefore, the present study systematically compares three frequently used polymers for the in vitro engineering of extracellular matrix based on poly-glycolic acid (PGA) under static as well as dynamic conditions. Ultra-structural analysis was used to examine the polymers structure. For tissue engineering (TE) three human fibroblast cell lines were seeded on either PGA-poly-4-hydroxybutyrate (P4HB), PGA-poly-lactic acid (PLA) or PGA-poly-caprolactone (PCL) patches. These patches were analyzed after 21days of culture qualitative by histology and quantitative by determining the amount of DNA, glycosaminoglycan and hydroxyproline. We found that PGA-P4HB and PGA-PLA scaffolds enhance tissue formation significantly higher than PGA-PCL scaffolds (p\<0.05). Polymer remnants were visualized by polarization microscopy. In addition, biomechanical properties of the tissue engineered patches were determined in comparison to native tissue. This study may allow future studies to specifically select certain polymer starter matrices aiming at specific tissue properties of the bioengineered constructs in vitro.}, url = {https://doi.org/10.1016/j.colsurfb.2017.06.046}, author = {101 - and Generali M and Kehl D and Capulli AK and Parker KK and Hoerstrup SP and Weber B} } @article {1625947, title = {Design and fabrication of fibrous nanomaterials using pull spinning}, journal = {Macromolecular Materials and Engineering}, volume = {302}, number = {3}, year = {2017}, pages = {1600404}, abstract = {The assembly of natural and synthetic polymers into fibrous nanomaterials has applications ranging from textiles, tissue engineering, photonics, and catalysis. However, rapid manufacturing of these materials is challenging, as the state of the art in nanofiber assembly remains limited by factors such as solution polarity, production rate, applied electric fields, or temperature. Here, the design and development of a rapid nanofiber manufacturing system termed pull spinning is described. Pull spinning is compact and portable, consisting of a high-speed rotating bristle that dips into a polymer or protein reservoir and pulls a droplet from solution into a nanofiber. When multiple layers of nanofibers are collected, they form a nonwoven network whose composition, orientation, and function can be adapted to multiple applications. The capability of pull spinning to function as a rapid, point-of-use fiber manufacturing platform is demonstrated for both muscle tissue engineering and textile design.}, url = {https://doi.org/10.1002/mame.201600404}, author = {100 - and Deravi LF and Sinatra NR and Chantre CO and Nesmith AP and Yuan H and Deravi SK and Goss JA and MacQueen LA and Badrossamy MR and Gonzalez GM and Phillips MD and Parker KK} } @article {1625957, title = {Fabrication of Millimeter-Long Carbon Tubular Nanostructures Using the Self-Rolling Process Inherent in Elastic Protein Layers}, journal = {Advanced Materials}, volume = {29}, number = {31}, year = {2017}, pages = {1701732}, abstract = {Millimeter-long conducting fibers can be fabricated from carbon nanomaterials via a simple method involving the release of a prestrained protein layer. This study shows how a self-rolling process initiated by polymerization of a micropatterned layer of fibronectin (FN) results in the production of carbon nanomaterial-based microtubular fibers. The process begins with deposition of carbon nanotube (CNT) or graphene oxide (GO) particles on the FN layer. Before polymerization, particles are discrete and nonconducting, but after polymerization the carbon materials become entangled to form an interconnected conducting network clad by FN. Selective removal of FN using high-temperature combustion yields freestanding CNT or reduced GO microtubular fibers. The properties of these fibers are characterized using atomic force microscopy and Raman spectroscopy. The data suggest that this method may provide a ready route to rapid design and fabrication of aligned biohybrid nanomaterials potentially useful for future electronic applications.}, url = {https://doi.org/10.1002/adma.201701732}, author = {99 - and Ko H and Deravi LF and Park SJ and Jang J and Lee T and Kang C and Lee JS and Parker KK and Shin K} } @article {1625948, title = {Instrumented cardiac microphysiological devices via multimaterial three-dimensional printing}, journal = {Nature Materials}, volume = {16}, number = {3}, year = {2017}, pages = {303-308}, abstract = {Biomedical research has relied on animal studies and conventional cell cultures for decades. Recently, microphysiological systems (MPS), also known as organs-on-chips, that recapitulate the structure and function of native tissues in vitro, have emerged as a promising alternative1. However, current MPS typically lack integrated sensors and their fabrication requires multi-step lithographic processes2. Here, we introduce a facile route for fabricating a new class of instrumented cardiac microphysiological devices via multimaterial three-dimensional (3D) printing. Specifically, we designed six functional inks, based on piezo-resistive, high-conductance, and biocompatible soft materials that enable integration of soft strain gauge sensors within micro-architectures that guide the self-assembly of physio-mimetic laminar cardiac tissues. We validated that these embedded sensors provide non-invasive, electronic readouts of tissue contractile stresses inside cell incubator environments. We further applied these devices to study drug responses, as well as the contractile development of human stem cell-derived laminar cardiac tissues over four weeks.}, url = {https://doi.org/10.1038/nmat4782}, author = {98 - and Lind JU and Busbee TA and Valentine AD and Pasqualini FS and Yuan H and Yadid M and Park SJ and Kotikian A and Nesmith AP and Campbell PH and Vlassak JJ and Lewis JA and Parker KK} } @article {1625951, title = {JetValve: Rapid manufacturing of biohybrid scaffolds for biomimetic heart valve replacement}, journal = {Biomaterials}, volume = {133}, year = {2017}, pages = {229-241}, abstract = {Tissue engineered scaffolds have emerged as a promising solution for heart valve replacement because of their potential for regeneration. However, traditional heart valve tissue engineering has relied on resource-intensive, cell-based manufacturing, which increases cost and hinders clinical translation. To overcome these limitations, in situ tissue engineering approaches aim to develop scaffold materials and manufacturing processes that elicit endogenous tissue remodeling and repair. Yet despite recent advances in synthetic materials manufacturing, there remains a lack of cell-free, automated approaches for rapidly producing biomimetic heart valve scaffolds. Here, we designed a jet spinning process for the rapid and automated fabrication of fibrous heart valve scaffolds. The composition, multiscale architecture, and mechanical properties of the scaffolds were tailored to mimic that of the native leaflet fibrosa and assembled into three dimensional, semilunar valve structures. We demonstrated controlled modulation of these scaffold parameters and show initial biocompatibility and functionality in vitro. Valves were minimally-invasively deployed via transapical access to the pulmonary valve position in an ovine model and shown to be functional for 15 h.}, url = {https://doi.org/10.1016/j.biomaterials.2017.04.033}, author = {97 - and Capulli AK and Emmert MY and Pasqualini FS and Kehl D and Caliskan E and Lind JU and Sheehy SP and Park SJ and Ahn S and Weber B and Goss JA and Hoerstrup SP and Parker KK} } @article {1625990, title = {Myofibrils in Cardiomyocytes Tend to Assemble Along the Maximal Principle Stress Directions}, journal = {Journal of Biomechanical Engineering}, volume = {139}, number = {12}, year = {2017}, pages = {1210101{\textendash}1210108}, abstract = {The mechanisms underlying the spatial organization of self-assembled myofibrils in cardiac tissues remain incompletely understood. By modeling cells as elastic solids under active cytoskeletal contraction, we found a good correlation between the predicted maximal principal stress directions and the in vitro myofibril orientations in individual cardiomyocytes. This implies that actomyosin fibers tend to assemble along the maximal tensile stress (MTS) directions. By considering the dynamics of focal adhesion and myofibril formation in the model, we showed that different patterns of myofibril organizations in mature versus immature cardiomyocytes can be explained as the consequence of the different levels of force-dependent remodeling of focal adhesions. Further, we applied the mechanics model to cell pairs and showed that the myofibril organizations can be regulated by a combination of multiple factors including cell shape, cell{\textendash}substrate adhesions, and cell{\textendash}cell adhesions. This mechanics model can guide the rational design in cardiac tissue engineering where recapitulating in vivo myofibril organizations is crucial to the contractile function of the heart.}, url = {https://dx.doi.org/10.1115\%2F1.4037795}, author = {96 - and Yuan H and Marzban B and Parker KK} } @article {1625949, title = {Neurons derived from different brain regions are inherently different in vitro: A novel multiregional brain-on-a-chip}, journal = {Journal of Neurophysiology}, volume = {117}, number = {3}, year = {2017}, pages = {1320-1341}, abstract = {Brain in vitro models are critically important to developing our understanding of basic nervous system cellular physiology, potential neurotoxic effects of chemicals, and specific cellular mechanisms of many disease states. In this study, we sought to address key shortcomings of current brain in vitro models: the scarcity of comparative data for cells originating from distinct brain regions and the lack of multiregional brain in vitro models. We demonstrated that rat neurons from different brain regions exhibit unique profiles regarding their cell composition, protein expression, metabolism, and electrical activity in vitro. In vivo, the brain is unique in its structural and functional organization, and the interactions and communication between different brain areas are essential components of proper brain function. This fact and the observation that neurons from different areas of the brain exhibit unique behaviors in vitro underline the importance of establishing multiregional brain in vitro models. Therefore, we here developed a multiregional brain-on-a-chip and observed a reduction of overall firing activity, as well as altered amounts of astrocytes and specific neuronal cell types compared with separately cultured neurons. Furthermore, this multiregional model was used to study the effects of phencyclidine, a drug known to induce schizophrenia-like symptoms in vivo, on individual brain areas separately while monitoring downstream effects on interconnected regions. Overall, this work provides a comparison of cells from different brain regions in vitro and introduces a multiregional brain-on-a-chip that enables the development of unique disease models incorporating essential in vivo features.NEW \& NOTEWORTHY Due to the scarcity of comparative data for cells from different brain regions in vitro, we demonstrated that neurons isolated from distinct brain areas exhibit unique behaviors in vitro. Moreover, in vivo proper brain function is dependent on the connection and communication of several brain regions, underlining the importance of developing multiregional brain in vitro models. We introduced a novel brain-on-a-chip model, implementing essential in vivo features, such as different brain areas and their functional connections.}, url = {https://doi.org/10.1152/jn.00575.2016}, author = {95 - and Dauth S and Maoz BM and Sheehy SP and Hemphill MA and Murty T and Macedonia MK and Greer AM and Budnik B and Parker KK} } @article {1625946, title = {Organ Chips: Quality Assurance Systems in Regenerative Medicine}, journal = {Clinical Pharmacology \& Therapeutics}, volume = {101}, number = {1}, year = {2017}, pages = {31-34}, abstract = {A class of novel therapies leverages regenerative cell types in disease microenvironments.[1] This complex interplay challenges established good manufacturing practices, as standards and analytical tools to measure regenerative potency are missing.[2] That is, we can build the product right, but we do not know if we are building the right product. Here, we suggest that organ-chips, biomimetic in-vitro phenotyping platforms,[3,4] can serve as key quality assurance systems in regenerative medicine.[1,2,5]}, url = {https://dx.doi.org/10.1002\%2Fcpt.527}, author = {94 - and Pasqualini FS and Emmert MY and Parker KK and Hoerstrup SP} } @article {1625956, title = {Organs-on-Chips with combined multi-electrode array and transepithelial electrical resistance measurement capabilities}, journal = {Lab Chip}, volume = {17}, number = {13}, year = {2017}, pages = {2294-2302}, abstract = {Here we demonstrate that microfluidic cell culture devices, known as Organs-on-a-Chips can be fabricated with multifunctional, real-time, sensing capabilities by integrating both multi-electrode arrays (MEAs) and electrodes for transepithelial electrical resistance (TEER) measurements into the chips during their fabrication. To prove proof-of-concept, simultaneous measurements of cellular electrical activity and tissue barrier function were carried out in a dual channel, endothelialized, heart-on-a-chip device containing human cardiomyocytes and a channel-separating porous membrane covered with a primary human endothelial cell monolayer. These studies confirmed that the TEER{\textendash}MEA chip can be used to simultaneously detect dynamic alterations of vascular permeability and cardiac function in the same chip when challenged with the inflammatory stimulus tumor necrosis factor alpha (TNF-α) or the cardiac targeting drug isoproterenol. Thus, this Organ Chip with integrated sensing capability may prove useful for real-time assessment of biological functions, as well as response to therapeutics.}, url = {https://doi.org/10.1039/C7LC00412E}, author = {93 - and Maoz BM and Herland A and Henry OYF and Leineweber WD and Yadid M and Doyle J and Mannix R and Kujala VJ and Fitzgerald EA and Parker KK and Ingber DE} } @article {1625942, title = {Production of synthetic, para-aramid and biopolymer nanofibers by immersion rotary jet-spinning}, journal = {Macromolecular Materials and Engineering}, volume = {302}, number = {1}, year = {2017}, pages = {1600365}, abstract = {Nanofiber production platforms commonly rely on volatile carrier solvents or high voltages. Production of nanofibers comprised of charged polymers or polymers requiring nonvolatile solvents thus typically requires customization of spinning setup and polymer dope. In severe cases, these challenges can hinder fiber formation entirely. Here, a versatile system is presented which addresses these challenges by employing centrifugal force to extrude polymer dope jet through an air gap, into a flowing precipitation bath. This voltage-free approach ensures that nanofiber solidification occurs in liquid, minimizing surface tension instability that results in jet breakup and fiber defects. In addition, nanofibers of controlled size and morphology can be fabricated by tuning spinning parameters including air gap length, spinning speed, polymer concentration, and bath composition. To demonstrate the versatility of our platform, para-aramid (e.g., Kevlar) and biopolymer (e.g., DNA, alginate) nanofibers are produced that cannot be readily produced using standard nanofiber production methods.}, url = {https://doi.org/10.1002/mame.201600365}, author = {92 - and Gonzalez GM and MacQueen LA and Lind JU and Fitzgibbons SA and Chantre CO and Huggler I and Golecki HM and Goss JA and Parker KK} } @article {1625950, title = {Safety and efficacy of cardiopoietic stem cells in the treatment of post-infarction left-ventricular dysfunction {\textendash} From cardioprotection to functional repair in a translational pig infarction model}, journal = {Biomaterials}, volume = {122}, year = {2017}, pages = {48-62}, abstract = {To date, clinical success of cardiac cell-therapies remains limited. To enhance the cardioreparative properties of stem cells, the concept of lineage-specification through cardiopoietic-guidance has been recently suggested. However, so far, only results from murine studies and from a clinical pilot-trial in chronic heart-failure (CHF) are available, while systematic evidence of its therapeutic-efficacy is still lacking. Importantly, also no data from large animals or for other indications are available. Therefore, we here investigate the therapeutic-efficacy of human cardiopoietic stem cells in the treatment of post-infarction LV-dysfunction using a translational pig-model. Using growth-factor priming, lineage-specification of human bone-marrow derived MSCs was achieved to generate cardiopoietic stem cells according to GMP-compliant protocols. Thereafter, pigs with post-infarction LV-dysfunction (sub-acute phase;1-month) were randomized to either receive transcatheter NOGA 3D electromechanical-mapping guided intramyocardial transplantation of cardiopoietic cells or saline (control). After 30days, cardiac MRI (cMRI) was performed for functional evaluation and in-vivo cell-tracking. This approach was coupled with a comprehensive post-mortem cell-fate and mode-of-repair analysis. Cardiopoietic cell therapy was safe and ejection-fraction was significantly higher when compared to controls (p = 0.012). It further prevented maladaptive LV-remodeling and revealed a significantly lower relative and total infarct-size (p = 0.043 and p = 0.012). As in-vivo tracking and post-mortem analysis displayed only limited intramyocardial cardiopoietic cell-integration, the significant induction of neo-angiogenesis (\~{}40\% higher; p = 0.003) and recruitment of endogenous progenitors (\~{}2.5x higher; p = 0.008) to the infarct border-zone appeared to be the major modes-of-repair. This is the first report using a pre-clinical large animal-model to demonstrate the safety and efficacy of cardiopoietic stem cells for the treatment of post-infarction LV-dysfunction to prevent negative LV-remodeling and subsequent CHF. It further provides insight into post-delivery cardiopoietic cell-fate and suggests the mechanisms of cardiopoietic cell-induced cardiac-repair. The adoption of GMP-/GLP-compliant methodologies may accelerate the translation into a phase-I clinical-trial in patients with post-ischemic LV-dysfunction broadening the current indication of this interesting cell-type.}, url = {https://doi.org/10.1016/j.biomaterials.2016.11.029}, author = {91 - and Emmert MY and Wolint P and Jakab A and Sheehy SP and Pasqualini FS and Nguyen TD and Hilbe M and Seifert B and Weber B and Brokopp CE and Macejovska D and Caliskan E and von Eckardstein A and Schwartlander R and Vogel V and Falk V and Parker KK and Gy{\"o}ngy{\"o}si M and Hoerstrup SP} } @article {1625960, title = {Toward improved myocardial maturity in an organ-on-chip platform with immature cardiac myocytes}, journal = {Experimental Biology and Medicine}, volume = {242}, number = {17}, year = {2017}, pages = {1643-1656}, abstract = {In vitro studies of cardiac physiology and drug response have traditionally been performed on individual isolated cardiomyocytes or isotropic monolayers of cells that may not mimic desired physiological traits of the laminar adult myocardium. Recent studies have reported a number of advances to Heart-on-a-Chip platforms for the fabrication of more sophisticated engineered myocardium, but cardiomyocyte immaturity remains a challenge. In the anisotropic musculature of the heart, interactions between cardiac myocytes, the extracellular matrix (ECM), and neighboring cells give rise to changes in cell shape and tissue architecture that have been implicated in both development and disease. We hypothesized that engineered myocardium fabricated from cardiac myocytes cultured in vitro could mimic the physiological characteristics and gene expression profile of adult heart muscle. To test this hypothesis, we fabricated engineered myocardium comprised of neonatal rat ventricular myocytes with laminar architectures reminiscent of that observed in the mature heart and compared their sarcomere organization, contractile performance characteristics, and cardiac gene expression profile to that of isolated adult rat ventricular muscle strips. We found that anisotropic engineered myocardium demonstrated a similar degree of global sarcomere alignment, contractile stress output, and inotropic concentration-response to the β-adrenergic agonist isoproterenol. Moreover, the anisotropic engineered myocardium exhibited comparable myofibril related gene expression to muscle strips isolated from adult rat ventricular tissue. These results suggest that tissue architecture serves an important developmental cue for building in vitro model systems of the myocardium that could potentially recapitulate the physiological characteristics of the adult heart. Impact statement With the recent focus on developing in vitro Organ-on-Chip platforms that recapitulate tissue and organ-level physiology using immature cells derived from stem cell sources, there is a strong need to assess the ability of these engineered tissues to adopt a mature phenotype. In the present study, we compared and contrasted engineered tissues fabricated from neonatal rat ventricular myocytes in a Heart-on-a-Chip platform to ventricular muscle strips isolated from adult rats. The results of this study support the notion that engineered tissues fabricated from immature cells have the potential to mimic mature tissues in an Organ-on-Chip platform.}, url = {https://doi.org/10.1177/1535370217701006}, author = {90 - and Sheehy SP and Grosberg A and Qin P and Behm DJ and Ferrier JP and Eagleson MA and Nesmith AP and Krull D and Falls JG and Campbell PH and McCain ML and Willette RN and Hu E and Parker KK} } @article {1625939, title = {Acute pergolide exposure stiffens engineered valve interstitial cell tissues and reduced contractility in vitro}, journal = {Cardiovascular Pathology}, volume = {25}, number = {4}, year = {2016}, pages = {316-324}, abstract = {Medications based on ergoline-derived dopamine and serotonin agonists are associated with off-target toxicities that include valvular heart disease (VHD). Reports of drug-induced VHD resulted in the withdrawal of appetite suppressants containing fenfluramine and phentermine from the US market in 1997 and pergolide, a Parkinson{\textquoteright}s disease medication, in 2007. Recent evidence suggests that serotonin receptor activity affected by these medications modulates cardiac valve interstitial cell activation and subsequent valvular remodeling, which can lead to cardiac valve fibrosis and dysfunction similar to that seen in carcinoid heart disease. Failure to identify these risks prior to market and continued use of similar drugs reaffirm the need to improve preclinical evaluation of drug-induced VHD. Here, we present two complimentary assays to measure stiffness and contractile stresses generated by engineered valvular tissues in vitro. As a case study, we measured the effects of acute (24 h) pergolide exposure to engineered porcine aortic valve interstitial cell (AVIC) tissues. Pergolide exposure led to increased tissue stiffness, but it decreased both basal and active contractile tone stresses generated by AVIC tissues. Pergolide exposure also disrupted AVIC tissue organization (i.e., tissue anisotropy), suggesting that the mechanical properties and contractile functionality of these tissues are governed by their ability to maintain their structure. We expect further use of these assays to identify off-target drug effects that alter the phenotypic balance of AVICs, disrupt their ability to maintain mechanical homeostasis, and lead to VHD.}, url = {https://doi.org/10.1016/j.carpath.2016.04.004}, author = {89 - and Capulli AK and MacQueen LA and O{\textquoteright}Connor BB and Dauth S and Parker KK} } @article {1625897, title = {Angiotensin II Induced Cardiac Dysfunction on a Chip.}, journal = {PLOS ONE}, volume = {1}, number = {1}, year = {2016}, pages = {e0146415}, abstract = {In vitro disease models offer the ability to study specific systemic features in isolation to better understand underlying mechanisms that lead to dysfunction. Here, we present a cardiac dysfunction model using angiotensin II (ANG II) to elicit pathological responses in a heart-on-a-chip platform that recapitulates native laminar cardiac tissue structure. Our platform, composed of arrays of muscular thin films (MTF), allows for functional comparisons of healthy and diseased tissues by tracking film deflections resulting from contracting tissues. To test our model, we measured gene expression profiles, morphological remodeling, calcium transients, and contractile stress generation in response to ANG II exposure and compared against previous experimental and clinical results. We found that ANG II induced pathological gene expression profiles including over-expression of natriuretic peptide B, Rho GTPase 1, and T-type calcium channels. ANG II exposure also increased proarrhythmic early after depolarization events and significantly reduced peak systolic stresses. Although ANG II has been shown to induce structural remodeling, we control tissue architecture via microcontact printing, and show pathological genetic profiles and functional impairment precede significant morphological changes. We assert that our in vitro model is a useful tool for evaluating tissue health and can serve as a platform for studying disease mechanisms and identifying novel therapeutics.}, url = {https://doi.org/10.1371/journal.pone.0146415}, author = {88 - and Horton RE and Yadid M and McCain and ML and Sheehy SP and Pasqualini FS and Park SJ and Cho A and Campbell P and Parker KK} } @article {1625898, title = {Coupling primary and stem cell-derived cardiomyocytes in an in vitro model of cardiac cell therapy}, journal = {Journal of Cell Biology}, volume = {212}, number = {4}, year = {2016}, pages = {389{\textendash}397}, abstract = {The efficacy of cardiac cell therapy depends on the integration of existing and newly formed cardiomyocytes. Here, we developed a minimal in vitro model of this interface by engineering two cell microtissues (μtissues) containing mouse cardiomyocytes, representing spared myocardium after injury, and cardiomyocytes generated from embryonic and induced pluripotent stem cells, to model newly formed cells. We demonstrated that weaker stem cell{\textendash}derived myocytes coupled with stronger myocytes to support synchronous contraction, but this arrangement required focal adhesion-like structures near the cell{\textendash}cell junction that degrade force transmission between cells. Moreover, we developed a computational model of μtissue mechanics to demonstrate that a reduction in isometric tension is sufficient to impair force transmission across the cell{\textendash}cell boundary. Together, our in vitro and in silico results suggest that mechanotransductive mechanisms may contribute to the modest functional benefits observed in cell-therapy studies by regulating the amount of contractile force effectively transmitted at the junction between newly formed and spared myocytes.}, url = {https://dx.doi.org/10.1083\%2Fjcb.201508026}, author = {87 - and Aratyn-Schaus Y and Pasqualini FS and Yuan H and McCain ML and Ye GJ and Sheehy SP and Campbell PH and Parker KK} } @article {1625899, title = {Extracellular matrix protein expression is brain region dependent}, journal = {The Journal of Comparative Neurology}, volume = {524}, number = {7}, year = {2016}, pages = {1309-36}, abstract = {In the brain, extracellular matrix (ECM) components form networks that contribute to structural and functional diversity. Maladaptive remodeling of ECM networks has been reported in neurodegenerative and psychiatric disorders, suggesting that the brain microenvironment is a dynamic structure. A lack of quantitative information about ECM distribution in the brain hinders an understanding of region-specific ECM functions and the role of ECM in health and disease. We hypothesized that each ECM protein as well as specific ECM structures, such as perineuronal nets (PNNs) and interstitial matrix, are differentially distributed throughout the brain, contributing to the unique structure and function in the various regions of the brain. To test our hypothesis, we quantitatively analyzed the distribution, colocalization, and protein expression of aggrecan, brevican, and tenascin-R throughout the rat brain utilizing immunohistochemistry and mass spectrometry analysis and assessed the effect of aggrecan, brevican, and/or tenascin-R on neurite outgrowth in vitro. We focused on aggrecan, brevican, and tenascin-R as they are especially expressed in the mature brain, and have established roles in brain development, plasticity, and neurite outgrowth. The results revealed a differentiated distribution of all three proteins throughout the brain and indicated that their presence significantly reduces neurite outgrowth in a 3D in vitro environment. These results underline the importance of a unique and complex ECM distribution for brain physiology and suggest that encoding the distribution of distinct ECM proteins throughout the brain will aid in understanding their function in physiology and in turn assist in identifying their role in disease. J. Comp. Neurol. 524:1309-1336, 2016. {\textcopyright} 2016 Wiley Periodicals, Inc.}, url = {https://doi.org/10.1002/cne.23965}, author = {86 - and Dauth S and Grevesse T and Pantazopoulos H and Campbell PH and Maoz BM and Berretta S and Parker KK} } @booklet {1625941, title = {Generation of human muscle fibers and satellite-like cells from human pluripotent stem cells in vitro}, journal = {Nature Protocols}, volume = {11}, number = {10}, year = {2016}, pages = {1833-50}, abstract = {Progress toward finding a cure for muscle diseases has been slow because of the absence of relevant cellular models and the lack of a reliable source of muscle progenitors for biomedical investigation. Here we report an optimized serum-free differentiation protocol to efficiently produce striated, millimeter-long muscle fibers together with satellite-like cells from human pluripotent stem cells (hPSCs) in vitro. By mimicking key signaling events leading to muscle formation in the embryo, in particular the dual modulation of Wnt and bone morphogenetic protein (BMP) pathway signaling, this directed differentiation protocol avoids the requirement for genetic modifications or cell sorting. Robust myogenesis can be achieved in vitro within 1 month by personnel experienced in hPSC culture. The differentiating culture can be subcultured to produce large amounts of myogenic progenitors amenable to numerous downstream applications. Beyond the study of myogenesis, this differentiation method offers an attractive platform for the development of relevant in vitro models of muscle dystrophies and drug screening strategies, as well as providing a source of cells for tissue engineering and cell therapy approaches.}, url = {https://doi.org/10.1038/nprot.2016.110}, author = {85 - and Chal J and Tanoury ZA and Hestin M and Gobert B and Aivio S,Hick A,Cherrier T and Nesmith AP and Parker KK and Pourqui{\'e} O} } @article {1625943, title = {A human in vitro model of Duchenne muscular dystrophy muscle formation and contractility}, journal = {The Journal of Cell Biology}, volume = {215}, number = {1}, year = {2016}, pages = {47-56}, abstract = {Tongue weakness, like all weakness in Duchenne muscular dystrophy (DMD), occurs as a result of contraction-induced muscle damage and deficient muscular repair. Although membrane fragility is known to potentiate injury in DMD, whether muscle stem cells are implicated in deficient muscular repair remains unclear. We hypothesized that DMD myoblasts are less sensitive to cues in the extracellular matrix designed to potentiate structure{\textendash}function relationships of healthy muscle. To test this hypothesis, we drew inspiration from the tongue and engineered contractile human muscle tissues on thin films. On this platform, DMD myoblasts formed fewer and smaller myotubes and exhibited impaired polarization of the cell nucleus and contractile cytoskeleton when compared with healthy cells. These structural aberrations were reflected in their functional behavior, as engineered tongues from DMD myoblasts failed to achieve the same contractile strength as healthy tongue structures. These data suggest that dystrophic muscle may fail to organize with respect to extracellular cues necessary to potentiate adaptive growth and remodeling.}, url = {https://dx.doi.org/10.1083\%2Fjcb.201603111}, author = {84 - and Nesmith AP and Wagner MA and Pasqualini FS and O{\textquoteright}Connor BB and Pincus MJ and August PR and Parker KK} } @article {1625937, title = {Laminar ventricular myocardium on a microelectrode array-based chip}, journal = {Journal of Materials Chemistry B}, volume = {4}, number = {20}, year = {2016}, pages = {3534-3543}, abstract = {Pharmaceutical screening based on human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and multi electrode arrays (MEAs) have been proposed as a complementary method for electrophysiological safety and efficacy assessment in drug discovery and development. Contrary to animal models, these cells offer a human genetic background but, at present, fail to recapitulate the mechanical and structural properties of the native human myocardium. Here, we report that topographical cues on soft micromolded gelatin can coax hiPSC-CMs to form laminar cardiac tissues that resemble the native architecture of the heart. Importantly, using this method we were able to record tissue-level electrophysiological responses with a commercially available MEA setup. To validate this platform, we recorded cardiac field potentials at baseline and after pharmacological interventions with a β-adrenergic agonist (isoproterenol). Further, we tested the ability of our system to predict the response of laminar human cardiac tissues to a cardiotoxic pro-drug (terfenadine) and its non-cardiotoxic metabolite (fexofenadine). Finally, we integrated our platform with microfluidic components to build a heart-on-a-chip system that can be fluidically linked with other organs-on-chips in the future.}, url = {https://doi.org/10.1039/C6TB00324A}, author = {90 - and Kujala VJ and Pasqualini FS and Goss JA and Nawroth JC and Parker KK} } @article {1625944, title = {Matched-Comparative Modeling of Normal and Diseased Human Airway Responses Using a Microengineered Breathing Lung Chip}, journal = {Cell Systems}, volume = {3}, number = {5}, year = {2016}, pages = {456-466}, abstract = {Smoking represents a major risk factor for chronic obstructive pulmonary disease (COPD), but it is difficult to characterize smoke-induced injury responses under physiological breathing conditions in humans due to patient-to-patient variability. Here, we show that a small airway-on-a-chip device lined by living human bronchiolar epithelium from normal or COPD patients can be connected to an instrument that "breathes" whole cigarette smoke in and out of the chips to study smoke-induced pathophysiology in vitro. This technology enables true matched comparisons of biological responses by culturing cells from the same individual with or without smoke exposure. These studies led to identification of ciliary micropathologies, COPD-specific molecular signatures, and epithelial responses to smoke generated by electronic cigarettes. The smoking airway-on-a-chip represents a tool to study normal and disease-specific responses of the human lung to inhaled smoke across molecular, cellular and tissue-level responses in an organ-relevant context.}, url = {https://doi.org/10.1016/j.cels.2016.10.003}, author = {83 - and Benam KH and Novak R and Nawroth J and Hirano-Kobayashi M and Ferrante TC and Choe Y and Prantil-Baun R and Weaver JC and Bahinski A and Parker KK and Ingber DE} } @article {1625945, title = {Mechanotransduction and Metabolism in Cardiomyocyte Microdomains}, journal = {BioMed Research International}, volume = {2016}, number = {4081638}, year = {2016}, abstract = {Efficient contractions of the left ventricle are ensured by the continuous transfer of adenosine triphosphate (ATP) from energy production sites, the mitochondria, to energy utilization sites, such as ionic pumps and the force-generating sarcomeres. To minimize the impact of intracellular ATP trafficking, sarcomeres and mitochondria are closely packed together and in proximity with other ultrastructures involved in excitation-contraction coupling, such as t-tubules and sarcoplasmic reticulum junctions. This complex microdomain has been referred to as the intracellular energetic unit. Here, we review the literature in support of the notion that cardiac homeostasis and disease are emergent properties of the hierarchical organization of these units. Specifically, we will focus on pathological alterations of this microdomain that result in cardiac diseases through energy imbalance and posttranslational modifications of the cytoskeletal proteins involved in mechanosensing and transduction.}, url = {https://doi.org/10.1155/2016/4081638}, author = {82 - and Pasqualini FS and Nesmith AP and Horton RE and Sheehy SP and Parker KK} } @article {1625940, title = {Microenvironmental control of adipocyte fate and function}, journal = {Trends in Cell Biology}, volume = {26}, number = {10}, year = {2016}, pages = {745-55}, url = {https://doi.org/10.1016/j.tcb.2016.05.005}, author = {81 - and Pope BD and Warren CR and Parker KK and Cowan CA} } @article {1625938, title = {Phototactic guidance of a tissue-engineered soft-robotic ray}, journal = {Science}, volume = {353}, number = {6295}, year = {2016}, pages = {158-162}, abstract = {Inspired by the relatively simple morphological blueprint provided by batoid fish such as stingrays and skates, we create a biohybrid system that enables an artificial animal, a tissue-engineered ray, to swim and phototactically follow a light cue. By patterning dissociated rat cardiac myocytes on an elastomeric body enclosing a microfabricated gold skeleton, we replicated fish morphology at one-tenth scale and captured basic fin deflection patterns of batoid fish. Optogenetics allows for phototactic guidance, steering and turning maneuvers. Optical stimulation induced sequential muscle activation via serpentine patterned muscle circuits leading to coordinated undulatory swimming. The speed and direction of the ray was controlled by modulating light frequency and by independently eliciting right and left fins, allowing the biohybrid machine to maneuver through an obstacle course. (125/125 max)}, url = {https://doi.org/10.1126/science.aaf4292}, author = {80 - and Park SJ and Gazzola M and Park KS and Park S and DiSanto V and Blevins EL and Lind JU and Campbell PH and Dauth S and Capulli AK and Pasqualini FS and Ahn S and Cho A and Yuan H and Maoz BM and Vijaykumar R and Choi JW and Deisseroth K and Lauder GV and Mahadevan L and Parker KK} } @article {1625895, title = {Cytoskeletal prestress regulates nuclear shape and stiffness in cardiac myocytes}, journal = {Experimental Biology and Medicine}, volume = {240}, number = {11}, year = {2015}, pages = {1543-54}, abstract = {Mechanical stresses on the myocyte nucleus have been associated with several diseases and potentially transduce mechanical stimuli into cellular responses. Although a number of physical links between the nuclear envelope and cytoplasmic filaments have been identified, previous studies have focused on the mechanical properties of individual components of the nucleus, such as the nuclear envelope and lamin network. The mechanical interaction between the cytoskeleton and chromatin on nuclear deformability remains elusive. Here, we investigated how cytoskeletal and chromatin structures influence nuclear mechanics in cardiac myocytes. Rapid decondensation of chromatin and rupture of the nuclear membrane caused a sudden expansion of DNA, a consequence of prestress exerted on the nucleus. To characterize the prestress exerted on the nucleus, we measured the shape and the stiffness of isolated nuclei and nuclei in living myocytes during disruption of cytoskeletal, myofibrillar, and chromatin structure. We found that the nucleus in myocytes is subject to both tensional and compressional prestress and its deformability is determined by a balance of those opposing forces. By developing a computational model of the prestressed nucleus, we showed that cytoskeletal and chromatin prestresses create vulnerability in the nuclear envelope. Our studies suggest the cytoskeletal-nuclear-chromatin interconnectivity may play an important role in mechanics of myocyte contraction and in the development of laminopathies by lamin mutations.}, url = {https://doi.org/10.1177/1535370215583799}, author = {79 - and Lee H and Adams WJ and Alford PW and McCain ML and Feinberg AW and Sheehy SP and Goss JA and Parker KK} } @article {1625891, title = {Diagnostic tools for evaluating the impact of Focal Axonal Swellings arising in neurodegenerative diseases and/or traumatic brain injury}, journal = {Journal of Neuroscience Methods}, volume = {30}, number = {253}, year = {2015}, pages = {233-243}, abstract = {Focal Axonal Swellings arise in several leading neurodegenerative diseases of the central nervous system and are hallmark features of concussions and traumatic brain injuries. Recent theories mapped how the shape of each swelling affects the propagation of spike trains and consequently the information encoded in them. Spikes can be selectively deleted, have their speed affected, or blocked depending upon the severity of the swelling.}, url = {https://doi.org/10.1016/j.jneumeth.2015.06.022}, author = {78 - and Maia PD and Hemphill MA and Zehnder B and Zhang C and Parker KK and Kutz JN} } @article {1625884, title = {Engineered in vitro disease models}, journal = {Annual Review of Pathology: Mechanisms of Disease}, volume = {10}, year = {2015}, pages = {195-262}, abstract = {The ultimate goal of most biomedical research is to gain greater insight into mechanisms of human disease or to develop new and improved therapies or diagnostics. Although great advances have been made in terms of developing disease models in animals, such as transgenic mice, many of these models fail to faithfully recapitulate the human condition. In addition, it is difficult to identify critical cellular and molecular contributors to disease or to vary them independently in whole-animal models. This challenge has attracted the interest of engineers, who have begun to collaborate with biologists to leverage recent advances in tissue engineering and microfabrication to develop novel in vitro models of disease. As these models are synthetic systems, specific molecular factors and individual cell types, including parenchymal cells, vascular cells, and immune cells, can be varied independently while simultaneously measuring system-level responses in real time. In this article, we provide some examples of these efforts, including engineered models of diseases of the heart, lung, intestine, liver, kidney, cartilage, skin and vascular, endocrine, musculoskeletal, and nervous systems, as well as models of infectious diseases and cancer. We also describe how engineered in vitro models can be combined with human inducible pluripotent stem cells to enable new insights into a broad variety of disease mechanisms, as well as provide a test bed for screening new therapies.}, url = {https://doi.org/10.1146/annurev-pathol-012414-040418}, author = {77 - and Benam KH and Dauth S and Hassell B and Herland A and Jain A and Jang KJ and Karalis K and Kim HJ and MacQueen L and Mahmoodian R and Musah S and Torisawa YS and van der Meer AD and Villenave R and Yadid M and Parker KK} } @article {1625896, title = {Fibrous scaffolds for building hearts and heart parts}, journal = {Advanced Drug Delivery Reviews}, volume = {96}, year = {2015}, pages = {83-102}, abstract = {Extracellular matrix (ECM) structure and biochemistry provide cell-instructive cues that promote and regulate tissue growth, function, and repair. From a structural perspective, the ECM is a scaffold that guides the self-assembly of cells into distinct functional tissues. The ECM promotes the interaction between individual cells and between different cell types, and increases the strength and resilience of the tissue in mechanically dynamic environments. From a biochemical perspective, factors regulating cell{\textendash}ECM adhesion have been described and diverse aspects of cell{\textendash}ECM interactions in health and disease continue to be clarified. Natural ECMs therefore provide excellent design rules for tissue engineering scaffolds. The design of regenerative three-dimensional (3D) engineered scaffolds is informed by the target ECM structure, chemistry, and mechanics, to encourage cell infiltration and tissue genesis. This can be achieved using nanofibrous scaffolds composed of polymers that simultaneously recapitulate 3D ECM architecture, high-fidelity nanoscale topography, and bio-activity. Their high porosity, structural anisotropy, and bio-activity present unique advantages for engineering 3D anisotropic tissues. Here, we use the heart as a case study and examine the potential of ECM-inspired nanofibrous scaffolds for cardiac tissue engineering. We asked: Do we know enough to build a heart? To answer this question, we tabulated structural and functional properties of myocardial and valvular tissues for use as design criteria, reviewed nanofiber manufacturing platforms and assessed their capabilities to produce scaffolds that meet our design criteria. Our knowledge of the anatomy and physiology of the heart, as well as our ability to create synthetic ECM scaffolds have advanced to the point that valve replacement with nanofibrous scaffolds may be achieved in the short term, while myocardial repair requires further study in vitro and in vivo.}, url = {https://doi.org/10.1016/j.addr.2015.11.020}, author = {76 - and Capulli AK and MacQueen LA and Sheehy SP and Parker KK} } @article {1625889, title = {Metrics for assessing cytoskeletal orientational correlations and consistency}, journal = {Public Library of Science Computational Biology}, volume = {11}, number = {4}, year = {2015}, pages = {e1004190}, abstract = {In biology, organization at multiple scales potentiates biological function. Current advances in staining and imaging of biological tissues provide a wealth of data, but there are few metrics to quantitatively describe these findings. In particular there is a need for a metric that would characterize the correlation and consistency of orientation of different biological constructs within a tissue. We aimed to create such a metric and to demonstrate its use with images of cardiac tissues. The co-orientational order parameter (COOP) was based on the mathematical framework of a classical parameter, the orientational order parameter (OOP). Theorems were proven to illustrate the properties and boundaries of the COOP, which was then applied to both synthetic and experimental data. We showed the COOP to be useful for quantifying the correlation of orientation of constructs such as actin filaments and sarcomeric Z-lines. As expected, cardiac tissues showed perfect correlation between actin filaments and Z-lines. We also demonstrated the use of COOP to quantify the consistency of construct orientation within cells of the same shape. The COOP provides a quantitative tool to characterize tissues beyond co-localization or single construct orientation distribution. In the future, this new parameter could be used to represent the quantitative changes during maturation of cardiac tissue, pathological malformation, and other processes.}, url = {https://doi.org/10.1371/journal.pcbi.1004190}, author = {75 - and Drew NK and Eagleson MA and Baldo DB Jr and Parker KK and Grosberg A} } @article {1625888, title = {Opposite rheological properties of neuronal microcompartments predict axonal vulnerability in brain injury}, journal = {Scientific Reports}, volume = {30}, number = {5}, year = {2015}, pages = {9475}, abstract = {Although pathological changes in axonal morphology have emerged as important features of traumatic brain injury (TBI), the mechanical vulnerability of the axonal microcompartment relative to the cell body is not well understood. We hypothesized that soma and neurite microcompartments exhibit distinct mechanical behaviors, rendering axons more sensitive to a mechanical injury. In order to test this assumption, we combined protein micropatterns with magnetic tweezer rheology to probe the viscoelastic properties of neuronal microcompartments. Creep experiments revealed two opposite rheological behaviors within cortical neurons: the cell body was soft and characterized by a solid-like response, whereas the neurite compartment was stiffer and viscous-like. By using pharmacological agents, we demonstrated that the nucleus is responsible for the solid-like behavior and the stress-stiffening response of the soma, whereas neurofilaments have a predominant contribution in the viscous behavior of the neurite. Furthermore, we found that the neurite is a mechanosensitive compartment that becomes softer and adopts a pronounced viscous state on soft matrices. Together, these findings highlight the importance of the regionalization of mechanical and rigidity-sensing properties within neuron microcompartments in the preferential damage of axons during traumatic brain injury and into potential mechanisms of axonal outgrowth after injury.}, url = {https://doi.org/10.1038/srep09475}, author = {74 - and Grevesse T and Dabiri BE and Parker KK and Gabriele S} } @article {1625890, title = {Self-organizing large-scale extracellular-matrix protein networks}, journal = {Advanced Materials}, volume = {27}, number = {18}, year = {2015}, pages = {2838-45}, abstract = {Spontaneous, highly ordered large-scale fibronectin networks driven by electrostatic polymer patterns are fabricated, and these precisely controlled protein connections are demonstrated. It is examined whether this scheme, universal to various fibrillar extracellular matrix proteins beyond fibronectin, collagen, and laminin, can be self-organized. These data reveal a novel bottom-up method to form anisotropic, free-standing protein networks to be used as flexible, transferrable substrates for cardiac and neuronal tissue engineering. {\textcopyright} 2015 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim.}, url = {https://doi.org/10.1002/adma.201405556}, author = {73 - and Ahn S and Deravi LF and Park SJ and Dabiri BE and Kim JS and Parker KK and Shin K} } @article {1625885, title = {Structural Phenotyping of Stem Cell Derived Cardiomyocytes}, journal = {Stem Cell Reports}, volume = {4}, number = {3}, year = {2015}, pages = {340-7}, abstract = {Structural phenotyping based on classical image feature detection has been adopted to elucidate the molecular mechanisms behind genetically or pharmacologically induced changes in cell morphology. Here, we developed a set of 11 metrics to capture the increasing sarcomere organization that occurs intracellularly during striated muscle cell development. To test our metrics, we analyzed the localization of the contractile protein α-actinin in a variety of primary and stem-cell derived cardiomyocytes. Further, we combined these metrics with data mining algorithms to unbiasedly score the phenotypic maturity of human-induced pluripotent stem cell-derived cardiomyocytes.}, url = {https://dx.doi.org/10.1016\%2Fj.stemcr.2015.01.020}, author = {72 - and Pasqualini FS and Sheehy SP and Agarwal A and Aratyn-Schaus Y and Parker KK} } @article {1625887, title = {Traumatic Brain Injury and the Neuronal Microenvironment: A Potential Role for Neuropathological Mechanotransduction}, journal = {Neuron}, volume = {86}, number = {6}, year = {2015}, pages = {1177-1192}, abstract = {Traumatic brain injury (TBI) is linked to several pathologies for which there is a lack of understanding of disease mechanisms and therapeutic strategies. To elucidate injury mechanisms, it is important to consider how physical forces are transmitted and transduced across all spatial scales of the brain. Although the mechanical response of the brain is typically characterized by its material properties and biological structure, cellular mechanotransduction mechanisms also exist. Such mechanisms can affect physiological processes by responding to exogenous mechanical forces directed through sub-cellular components, such as extracellular matrix and cell adhesion molecules, to mechanosensitive intracellular structures that regulate mechanochemical signaling pathways. We suggest that cellular mechanotransduction may be an important mechanism underlying the initiation of cell and sub-cellular injuries ultimately responsible for the diffuse pathological damage and clinical symptoms observed in TBI, thereby providing potential therapeutic opportunities not previously explored in TBI.}, url = {https://doi.org/10.1016/j.neuron.2015.02.041}, author = {71 - and Hemphill MA and Dauth S and Yu CJ and Dabiri BE and Parker KK} } @article {1625881, title = {Approaching the in vitro clinical trial: engineering organs on chips}, journal = {Lab Chip}, volume = {14}, number = {17}, year = {2014}, pages = {3181-6}, abstract = {In vitro cell culture and animal models are the most heavily relied upon tools of the pharmaceutical industry. When these tools fail, the results are costly and have at times, proven deadly. One promising new tool to enhance preclinical development of drugs is Organs on Chips (OOCs), proposed as a clinically and physiologically relevant means of modeling health and disease. Bringing the patient from bedside to bench in this form requires that the design, build, and test of OOCs be founded in clinical observations and methods. By creating OOCs as models of the patient, the industry may be better positioned to evaluate medicinal therapeutics.}, url = {https://doi.org/10.1039/c4lc00276h}, author = {70 - and Capulli AK and Tian K and Mehandru N and Bukhta A, and Choudhury SF and Suchyta M and Parker KK} } @article {1625836, title = {The contractile strength of vascular smooth muscle myocytes is shape dependent}, journal = {Integrative Biology}, volume = {6}, number = {2}, year = {2014}, pages = {152-163}, abstract = {Vascular smooth muscle cells in muscular arteries are more elongated than those in elastic arteries. Previously, we reported changes in the contractility of engineered vascular smooth muscle tissue that appeared to be correlated with the shape of the constituent cells, supporting the commonly held belief that elongated muscle geometry may allow for the better contractile tone modulation required in response to changes in blood flow and pressure. To test this hypothesis more rigorously, we developed an in vitro model by engineering human vascular smooth muscle cells to take on the same shapes as those seen in elastic and muscular arteries and measured their contraction during stimulation with endothelin-1. We found that in the engineered cells, actin alignment and nuclear eccentricity increased as the shape of the cell elongated. Smooth muscle cells with elongated shapes exhibited lower contractile strength but greater percentage increase in contraction after endothelin-1 stimulation. We analysed the relationship between smooth muscle contractility and subcellular architecture and found that changes in contractility were correlated with actin alignment and nuclear shape. These results suggest that elongated smooth muscle cells facilitate muscular artery tone modulation by increasing its dynamic contractile range.}, url = {https://doi.org/10.1039/c3ib40230d}, author = {69 - and Ye GJC and Aratyn-Schaus Y and Aratyn-Schaus Y and Nesmith AP and Pasqualini FS and Alford PW and Parker KK} } @article {1625883, title = {Effect of solvent evaporation on fiber morphology in rotary jet spinning}, journal = {Langmuir}, volume = {30}, number = {44}, year = {2014}, pages = {13369-74}, abstract = {The bulk production of polymeric nanofibers is important for fabricating high-performance, nanoscale materials. Rotary jet spinning (RJS) enables the mass production of nanostructured fibers by centrifugal forces but may result in inconsistent surface morphologies. Because nanofiber performance is dependent upon its surface features, we asked which parameters must be optimized during production to control fiber morphology. We developed and tested a mathematical model that describes how the competition between fluid instability and solvent removal in RJS regulates the degree of beading in fibers. Our data suggest that solvent evaporation during the spinning process causes an increase in jet viscosity and that these changes inhibit both bead formation and jet thinning. The RJS was used to vary experimental parameters, showing that fiber beading can be reduced by increasing solvent volatility, solution viscosity, and spinning velocity. Collectively, our results demonstrate that nanofiber morphology and diameter can be precisely controlled during RJS manufacturing.}, url = {https://doi.org/10.1021/la5023104}, author = {68 - and Golecki HM and Yuan H and Glavin C and Potter B and Badrossamay MR and Goss JA and Phillips MD and Parker KK} } @article {1625837, title = {Engineering hybrid polymer-protein super-aligned nanofibers via rotary jet spinning}, journal = {Biomaterials}, volume = {35}, number = {10}, year = {2014}, pages = {3188-97}, abstract = {Cellular microenvironments are important in coaxing cells to behave collectively as functional, structured tissues. Important cues in this microenvironment are the chemical, mechanical and spatial arrangement of the supporting matrix in the extracellular space. In engineered tissues, synthetic scaffolding provides many of these microenvironmental cues. Key requirements are that synthetic scaffolds should recapitulate the native three-dimensional (3D) hierarchical fibrillar structure, possess biomimetic surface properties and demonstrate mechanical integrity, and in some tissues, anisotropy. Electrospinning is a popular technique used to fabricate anisotropic nanofiber scaffolds. However, it suffers from relatively low production rates and poor control of fiber alignment without substantial modifications to the fiber collector mechanism. Additionally, many biomaterials are not amenable for fabrication via high-voltage electrospinning methods. Hence, we reasoned that we could utilize rotary jet spinning (RJS) to fabricate highly aligned hybrid protein-polymer with tunable chemical and physical properties. In this study, we engineered highly aligned nanofiber constructs with robust fiber alignment from blends of the proteins collagen and gelatin, and the polymer poly-ε-caprolactone via RJS and electrospinning. RJS-spun fibers retain greater protein content on the surface and are also fabricated at a higher production rate compared to those fabricated via electrospinning. We measured increased fiber diameter and viscosity, and decreasing fiber alignment as protein content increased in RJS hybrid fibers. RJS nanofiber constructs also demonstrate highly anisotropic mechanical properties mimicking several biological tissue types. We demonstrate the bio-functionality of RJS scaffold fibers by testing their ability to support cell growth and maturation with a variety of cell types. Our highly anisotropic RJS fibers are therefore able to support cellular alignment, maturation and self-organization. The hybrid nanofiber constructs fabricated by RJS therefore have the potential to be used as scaffold material for a wide variety of biological tissues and organs, as an alternative to electrospinning.}, url = {https://doi.org/10.1016/j.biomaterials.2013.12.072}, author = {67 - and Badrossamay MR and Balachandran K and Capulli AK and Golecki HM and Agarwal A and Goss JA and Kim H and Shin K and Parker KK} } @article {1625882, title = {Human airway musculature on a chip: an in vitro model of allergic asthmatic bronchoconstriction and bronchodilation}, journal = {Lab Chip}, volume = {14}, number = {20}, year = {2014}, pages = {3925-3936}, abstract = {Many potential new asthma therapies that show promise in the pre-clinical stage of drug development do not demonstrate efficacy during clinical trials. One factor contributing to this problem is the lack of human-relevant models of the airway that recapitulate the tissue-level structural and functional phenotypes of asthma. Hence, we sought to build a model of a human airway musculature on a chip that simulates healthy and asthmatic bronchoconstriction and bronchodilation in vitro by engineering anisotropic, laminar bronchial smooth muscle tissue on elastomeric thin films. In response to a cholinergic agonist, the muscle layer contracts and induces thin film bending, which serves as an in vitro analogue for bronchoconstriction. To mimic asthmatic inflammation, we exposed the engineered tissues to interleukin-13, which resulted in hypercontractility and altered relaxation in response to cholinergic challenge, similar to responses observed clinically in asthmatic patients as well as in studies with animal tissue. Moreover, we reversed asthmatic hypercontraction using a muscarinic antagonist and a β-agonist which are used clinically to relax constricted airways. Importantly, we demonstrated that targeting RhoA-mediated contraction using HA1077 decreased basal tone, prevented hypercontraction, and improved relaxation of the engineered tissues exposed to IL-13. These data suggest that we can recapitulate the structural and functional hallmarks of human asthmatic musculature on a chip, including responses to drug treatments for evaluation of safety and efficacy of new drugs. Further, our airway musculature on a chip provides an important tool for enabling mechanism-based search for new therapeutic targets through the ability to evaluate engineered muscle at the levels of protein expression, tissue structure, and tissue function.}, url = {https://doi.org/10.1039/c4lc00688g}, author = {66 - and Nesmith AP and Agarwal A and McCain ML and Parker KK} } @article {1625877, title = {Matrix elasticity regulates the optimal cardiac myocyte shape for contractility}, journal = {American Journal of Physiology-Heart and Circulatory Physiology}, volume = {306}, number = {11}, year = {2014}, pages = {H1525-H1539}, abstract = {Concentric hypertrophy is characterized by ventricular wall thickening, fibrosis, and decreased myocyte length-to-width aspect ratio. Ventricular thickening is considered compensatory because it reduces wall stress, but the functional consequences of cell shape remodeling in this pathological setting are unknown. We hypothesized that decreases in myocyte aspect ratio allow myocytes to maximize contractility when the extracellular matrix becomes stiffer due to conditions such as fibrosis. To test this, we engineered neonatal rat ventricular myocytes into rectangles mimicking the 2-D profiles of healthy and hypertrophied myocytes on hydrogels with moderate (13 kPa) and high (90 kPa) elastic moduli. Actin alignment was unaffected by matrix elasticity, but sarcomere content was typically higher on stiff gels. Microtubule polymerization was higher on stiff gels, implying increased intracellular elastic modulus. On moderate gels, myocytes with moderate aspect ratios (\~{}7:1) generated the most peak systolic work compared with other cell shapes. However, on stiffer gels, low aspect ratios (\~{}2:1) generated the most peak systolic work. To compare the relative contributions of intracellular vs. extracellular elasticity to contractility, we developed an analytical model and used our experimental data to fit unknown parameters. Our model predicted that matrix elasticity dominates over intracellular elasticity, suggesting that the extracellular matrix may potentially be a more effective therapeutic target than microtubules. Our data and model suggest that myocytes with lower aspect ratios have a functional advantage when the elasticity of the extracellular matrix decreases due to conditions such as fibrosis, highlighting the role of the extracellular matrix in cardiac disease.}, url = {https://doi.org/10.1152/ajpheart.00799.2013}, author = {65 - and McCain ML and Yuan H and Pasqualini FS and Campbell PH and Parker KK} } @article {1625879, title = {Micromolded gelatin hydrogels for extended culture of engineered cardiac tissues}, journal = {Biomaterials}, volume = {35}, number = {21}, year = {2014}, pages = {5462-71}, abstract = {Defining the chronic cardiotoxic effects of drugs during preclinical screening is hindered by the relatively short lifetime of functional cardiac tissues in vitro, which are traditionally cultured on synthetic materials that do not recapitulate the cardiac microenvironment. Because collagen is the primary extracellular matrix protein in the heart, we hypothesized that micromolded gelatin hydrogel substrates tuned to mimic the elastic modulus of the heart would extend the lifetime of engineered cardiac tissues by better matching the native chemical and mechanical microenvironment. To measure tissue stress, we used tape casting, micromolding, and laser engraving to fabricate gelatin hydrogel muscular thin film cantilevers. Neonatal rat cardiac myocytes adhered to gelatin hydrogels and formed aligned tissues as defined by the microgrooves. Cardiac tissues could be cultured for over three weeks without declines in contractile stress. Myocytes on gelatin had higher spare respiratory capacity compared to those on fibronectin-coated PDMS, suggesting that improved metabolic function could be contributing to extended culture lifetime. Lastly, human induced pluripotent stem cell-derived cardiac myocytes adhered to micromolded gelatin surfaces and formed aligned tissues that remained functional for four weeks, highlighting their potential for human-relevant chronic studies.}, url = {https://doi.org/10.1016/j.biomaterials.2014.03.052}, author = {64 - and McCain ML and Agarwal A and Nesmith HW and Nesmith AP and Parker KK} } @article {1625876, title = {Modeling the mitochondrial cardiomyopathy of Barth syndrome with induced pluripotent stem cell and heart-on-chip technologies}, journal = {Nature Medicine}, volume = {20}, number = {6}, year = {2014}, pages = {616-23}, abstract = {Study of monogenic mitochondrial cardiomyopathies may yield insights into mitochondrial roles in cardiac development and disease. Here, we combined patient-derived and genetically engineered induced pluripotent stem cells (iPSCs) with tissue engineering to elucidate the pathophysiology underlying the cardiomyopathy of Barth syndrome (BTHS), a mitochondrial disorder caused by mutation of the gene encoding tafazzin (TAZ). Using BTHS iPSC-derived cardiomyocytes (iPSC-CMs), we defined metabolic, structural and functional abnormalities associated with TAZ mutation. BTHS iPSC-CMs assembled sparse and irregular sarcomeres, and engineered BTHS {\textquoteright}heart-on-chip{\textquoteright} tissues contracted weakly. Gene replacement and genome editing demonstrated that TAZ mutation is necessary and sufficient for these phenotypes. Sarcomere assembly and myocardial contraction abnormalities occurred in the context of normal whole-cell ATP levels. Excess levels of reactive oxygen species mechanistically linked TAZ mutation to impaired cardiomyocyte function. Our study provides new insights into the pathogenesis of Barth syndrome, suggests new treatment strategies and advances iPSC-based in vitro modeling of cardiomyopathy.}, url = {https://doi.org/10.1038/nm.3545}, author = {63 - and Wang G and McCain ML and Yang L and He A and Pasqualini FS and Agarwal A and Yuan H and Jiang D and Zhang D and Zangi L and Geva J and Roberts AE and Ma Q and Ding J and Chen J and Wang DZ and Li K and Wang J and Wanders RJ and Kulik W and Vaz FM and Laflamme MA and Murry CE and Chien KR and Kelley RI and Church GM and Parker KK and Pu WT} } @article {1625838, title = {Quality Metrics for Stem Cell-Derived Cardiac Myocytes}, journal = {Stem Cell Reports}, volume = {6}, number = {23}, year = {2014}, pages = {282-294}, abstract = {Advances in stem cell manufacturing methods have made it possible to produce stem cell-derived cardiac myocytes at industrial scales for in vitro muscle physiology research purposes. Although FDA-mandated quality assurance metrics address safety issues in the manufacture of stem cell-based products, no standardized guidelines currently exist for the evaluation of stem cell-derived myocyte functionality. As a result, it is unclear whether the various stem cell-derived myocyte cell lines on the market perform similarly, or whether any of them accurately recapitulate the characteristics of native cardiac myocytes. We propose a multiparametric quality assessment rubric in which genetic, structural, electrophysiological, and contractile measurements are coupled with comparison against values for these measurements that are representative of the ventricular myocyte phenotype. We demonstrated this procedure using commercially available, mass-produced murine embryonic stem cell- and induced pluripotent stem cell-derived myocytes compared with a neonatal mouse ventricular myocyte target phenotype in coupled in vitro assays.}, url = {https://doi.org/10.1016/j.stemcr.2014.01.015}, author = {62 - and Sheehy SP and Pasqualini F and Grosberg A and Park SJ and Yvonne Aratyn-Schaus Y and Parker KK} } @article {1625880, title = {The role of mechanotransduction on vascular smooth muscle myocytes cytoskeleton and contractile function}, journal = {Anatomical Record}, volume = {297}, number = {9}, year = {2014}, pages = {1758-69}, abstract = {Smooth muscle exhibits a highly organized structural hierarchy that extends over multiple spatial scales to perform a wide range of functions at the cellular, tissue, and organ levels. Early efforts primarily focused on understanding vascular smooth muscle function through biochemical signaling. However, accumulating evidence suggests that mechanotransduction, the process through which cells convert mechanical stimuli into biochemical cues, is requisite for regulating contractility. Cytoskeletal proteins that comprise the extracellular, intercellular, and intracellular domains are mechanosensitive and can remodel their structure and function in response to external mechanical cues. Pathological stimuli such as malignant hypertension can act through the same mechanotransductive pathways to induce maladaptive remodeling, leading to changes in cellular shape and loss of contractile function. In both health and disease, the cytoskeletal architecture integrates the mechanical stimuli and mediates structural and functional remodeling in the vascular smooth muscle.}, url = {https://dx.doi.org/10.1002\%2Far.22983}, author = {61 - and Ye GJ and Nesmith AP and Parker KK} } @article {1625835, title = {The structure-function relationships of a natural nanoscale photonic device in cuttlefish chromatophores}, journal = {Journal of The Royal Society Interface}, volume = {11}, number = {93}, year = {2014}, pages = {20130942}, abstract = {Cuttlefish, Sepia officinalis, possess neurally controlled, pigmented chromatophore organs that allow rapid changes in skin patterning and coloration in response to visual cues. This process of adaptive coloration is enabled by the 500\% change in chromatophore surface area during actuation. We report two adaptations that help to explain how colour intensity is maintained in a fully expanded chromatophore when the pigment granules are distributed maximally: (i) pigment layers as thin as three granules that maintain optical effectiveness and (ii) the presence of high-refractive-index proteins{\textemdash}reflectin and crystallin{\textemdash}in granules. The latter discovery, combined with our finding that isolated chromatophore pigment granules fluoresce between 650 and 720 nm, refutes the prevailing hypothesis that cephalopod chromatophores are exclusively pigmentary organs composed solely of ommochromes. Perturbations to granular architecture alter optical properties, illustrating a role for nanostructure in the agile, optical responses of chromatophores. Our results suggest that cephalopod chromatophore pigment granules are more complex than homogeneous clusters of chromogenic pigments. They are luminescent protein nanostructures that facilitate the rapid and sophisticated changes exhibited in dermal pigmentation.}, url = {https://doi.org/10.1098/rsif.2013.0942}, author = {60 - and Deravi LF and Magyar AP and Sheehy SP and Bell GRR and M{\"a}thger LM and Senfta SL and Wardill TJ and Lane WS and Kuzirian AM and Hanlon RT and Hu EL and Parker KK} } @article {1625878, title = {Three-Dimensional Paper-Based Model for Cardiac Ischemia}, journal = {Advanced Healthcare Materials}, volume = {3}, number = {7}, year = {2014}, pages = {1036-43}, abstract = {In vitro models of ischemia have not historically recapitulated the cellular interactions and gradients of molecules that occur in a 3D tissue. This work demonstrates a paper-based 3D culture system that mimics some of the interactions that occur among populations of cells in the heart during ischemia. Multiple layers of paper containing cells, suspended in hydrogels, are stacked to form a layered 3D model of a tissue. Mass transport of oxygen and glucose into this 3D system can be modulated to induce an ischemic environment in the bottom layers of the stack. This ischemic stress induces cardiomyocytes at the bottom of the stack to secrete chemokines which subsequently trigger fibroblasts residing in adjacent layers to migrate toward the ischemic region. This work demonstrates the usefulness of patterned, stacked paper for performing in vitro mechanistic studies of cellular motility and viability within a model of the laminar ventricle tissue of the heart.}, url = {https://doi.org/10.1002/adhm.201300575}, author = {59 - and Mosadegh B and Dabiri BE and Lockett MR and Derda R and Campbell P and Parker KK and Whitesides GM} } @article {1625834, title = {Design standards for engineered tissues}, journal = {Biotechnology Advances}, volume = {31}, number = {5}, year = {2013}, pages = {632-7}, abstract = {Traditional technologies are required to meet specific, quantitative standards of safety and performance. In tissue engineering, similar standards will have to be developed to enable routine clinical use and customized tissue fabrication. In this essay, we discuss a framework of concepts leading towards general design standards for tissue-engineering, focusing in particular on systematic design strategies, control of cell behavior, physiological scaling, fabrication modes and functional evaluation.}, url = {https://dx.doi.org/10.1016\%2Fj.biotechadv.2012.12.005}, author = {58 - and Nawroth JC and Parker KK} } @article {1625833, title = {Microfluidic heart on a chip for higher throughput pharmacological studies}, journal = {Lab on a Chip}, volume = {13}, number = {18}, year = {2013}, pages = {3599-608}, abstract = {We present the design of a higher throughput {\textquotedblleft}heart on a chip{\textquotedblright} which utilizes a semi-automated fabrication technique to process sub millimeter sized thin film cantilevers of soft elastomers. Anisotropic cardiac microtissues which recapitulate the laminar architecture of the heart ventricle are engineered on these cantilevers. Deflection of these cantilevers, termed Muscular Thin Films (MTFs), during muscle contraction allows calculation of diastolic and systolic stresses generated by the engineered tissues. We also present the design of a reusable one channel fluidic microdevice completely built out of autoclavable materials which incorporates various features required for an optical cardiac contractility assay: metallic base which fits on a heating element for temperature control, transparent top for recording cantilever deformation and embedded electrodes for electrical field stimulation of the tissue. We employ the microdevice to test the positive inotropic effect of isoproterenol on cardiac contractility at dosages ranging from 1 nM to 100 μM. The higher throughput fluidic heart on a chip has applications in testing of cardiac tissues built from rare or expensive cell sources and for integration with other organ mimics. These advances will help alleviate translational barriers for commercial adoption of these technologies by improving the throughput and reproducibility of readout, standardization of the platform and scalability of manufacture.}, url = {https://dx.doi.org/10.1039\%2Fc3lc50350j}, author = {57 - and Agarwal A and Goss JA and Cho A and McCain ML and Parker KK} } @article {1625832, title = {Micropatterning Alginate Substrates for In Vitro Cardiovascular Muscle on a Chip}, journal = {Advanced Functional Materials}, volume = {23}, number = {30}, year = {2013}, pages = {3738-46}, abstract = {Soft hydrogels such as alginate are ideal substrates for building muscle in vitro because they have structural and mechanical properties close to the in vivo extracellular matrix (ECM) network. However, hydrogels are generally not amenable to protein adhesion and patterning. Moreover, muscle structures and their underlying ECM are highly anisotropic, and it is imperative that in vitro models recapitulate the structural anisotropy in reconstructed tissues for in vivo relevance due to the tight coupling between sturcture and function in these systems. We present two techniques to create chemical and structural heterogeneities within soft alginate substrates and employ them to engineer anisotropic muscle monolayers: (i) microcontact printing lines of extracellular matrix proteins on flat alginate substrates to guide cellular processes with chemical cues, and (ii) micromolding of alginate surface into grooves and ridges to guide cellular processes with topographical cues. Neonatal rat ventricular myocytes as well as human umbilical artery vascular smooth muscle cells successfully attach to both these micropatterned substrates leading to subsequent formation of anisotropic striated and smooth muscle tissues. Muscular thin film cantilevers cut from these constructs are then employed for functional characterization of engineered muscular tissues. Thus, micropatterned alginate is an ideal substrate for in vitro models of muscle tissue because it facilitates recapitulation of the anisotropic architecture of muscle, mimics the mechanical properties of the ECM microenvironment, and is amenable to evaluation of functional contractile properties.}, url = {https://doi.org/10.1002/adfm.201203319}, author = {56 - and Agarwal A and Farouz Y and Nesmith AP and Deravi LF and McCain ML and Parker KK} } @article {1625830, title = {Protein-Based Textiles: Bio-Inspired and Bio-Derived Materials for Medical and Non-Medical Applications}, journal = {Journal of Chemical and Biological Interfaces}, volume = {1}, number = {1}, year = {2013}, pages = {25-34}, abstract = {The hierarchical structure-dependent function of self-assembling proteins regulates the biochemical and mechanical functions of cells, tissues, and organs. These multi-scale properties make proteins desirable candidates for novel supramolecular materials that require tailored properties and customizable functions. The ability to translate molecular domains of proteins into the bulk production of conformable materials, such as textiles, is restricted by the current limitations in fabrication technologies and the finite abundance of protein starting material. We will review the common features of self-assembling proteins, including their structure-dependent mechanical properties and how these characteristics have inspired techniques for manufacturing protein-based textiles. These technologies coupled with recent advances in recombinant protein synthesis enable the bulk production of fibers and fabrics that emulate the hierarchical function of natural protein networks.}, url = {https://doi.org/10.1166/jcbi.2013.1009}, author = {55 - and Deravi LF and Golecki HM and Parker KK} } @article {1625831, title = {Recapitulating maladaptive, multiscale remodeling of failing myocardium on a chip}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {110}, number = {24}, year = {2013}, pages = {9770-9775}, abstract = {The lack of a robust pipeline of medical therapeutic agents for the treatment of heart disease may be partially attributed to the lack of in vitro models that recapitulate the essential structure-function relationships of healthy and diseased myocardium. We designed and built a system to mimic mechanical overload in vitro by applying cyclic stretch to engineered laminar ventricular tissue on a stretchable chip. To test our model, we quantified changes in gene expression, myocyte architecture, calcium handling, and contractile function and compared our results vs. several decades of animal studies and clinical observations. Cyclic stretch activated gene expression profiles characteristic of pathological remodeling, including decreased α- to β-myosin heavy chain ratios, and induced maladaptive changes to myocyte shape and sarcomere alignment. In stretched tissues, calcium transients resembled those reported in failing myocytes and peak systolic stress was significantly reduced. Our results suggest that failing myocardium, as defined genetically, structurally, and functionally, can be replicated in an in vitro microsystem by faithfully recapitulating the structural and mechanical microenvironment of the diseased heart.}, url = {https://doi.org/10.1073/pnas.1304913110}, author = {54 - and McCain ML and Sheehy SP and Grosberg A and Goss JA and Parker KK} } @article {1625818, title = {Cell-to-cell coupling in engineered pairs of rat ventricular cardiomyocytes: relation between Cx43 immunofluorescence and intercellular electrical conductance}, journal = {American Journal of Physiology-Heart and Circulatory Physiology}, volume = {302}, number = {2}, year = {2012}, pages = {H443-H450}, abstract = {Gap junctions are composed of connexin (Cx) proteins, which mediate intercellular communication. Cx43 is the dominant Cx in ventricular myocardium, and Cx45 is present in trace amounts. Cx43 immunosignal has been associated with cell-to-cell coupling and electrical propagation, but no studies have directly correlated Cx43 immunosignal to electrical cell-to-cell conductance, g(j), in ventricular cardiomyocyte pairs. To assess the correlation between Cx43 immunosignal and g(j), we developed a method to determine both parameters from the same cell pair. Neonatal rat ventricular cardiomyocytes were seeded on micropatterned islands of fibronectin. This allowed formation of cell pairs with reproducible shapes and facilitated tracking of cell pair locations. Moreover, cell spreading was limited by the fibronectin pattern, which allowed us to increase cell height by reducing the surface area of the pattern. Whole cell dual voltage clamp was used to record g(j) of cell pairs after 3-5 days in culture. Fixation of cell pairs before removal of patch electrodes enabled preservation of cell morphology and offline identification of patched pairs. Subsequently, pairs were immunostained, and the volume of junctional Cx43 was quantified using confocal microscopy, image deconvolution, and three-dimensional reconstruction. Our results show a linear correlation between g(j) and Cx43 immunosignal within a range of 8-50 nS.}, url = {https://doi.org/10.1152/ajpheart.01218.2010}, author = {53 - and McCain ML and Desplantez T and Geisse NA and Rothen-Rutishauser B and Oberer H and Parker KK and Kleber AG} } @article {1625820, title = {Connexin43 ablation in foetal atrial myocytes decreases electrical coupling, partner connexins, and sodium current.}, journal = {Cardiovascular Research}, volume = {94}, number = {1}, year = {2012}, pages = {58-65}, abstract = {Remodelling and regional gradients in expression of connexins (Cx) are thought to contribute to atrial electrical dysfunction and atrial fibrillation. We assessed the effect of interaction between Cx43, Cx40, and Cx45 on atrial cell-to-cell coupling and inward Na current (INa) in engineered pairs of atrial myocytes derived from wild-type mice (Cx43+/+) and mice with genetic ablation of Cx43 (Cx43-/-).}, url = {https://doi.org/10.1093/cvr/cvs025}, author = {52 - and Desplantez T and McCain ML and Beauchamp P and Rigoli G and Rothen-Rutishauser B and Parker KK and Kleber AG} } @article {1625827, title = {The contribution of cellular mechanotransduction to cardiomyocyte form and function}, journal = {Biomechanics and Modeling in Mechanobiology}, volume = {11}, number = {8}, year = {2012}, pages = {1227-1239}, abstract = {Myocardial development is regulated by an elegantly choreographed ensemble of signaling events mediated by a multitude of intermediates that take a variety of forms. Cellular differentiation and maturation are a subset of vertically integrated processes that extend over several spatial and temporal scales to create a well-defined collective of cells that are able to function cooperatively and reliably at the organ level. Early efforts to understand the molecular mechanisms of cardiomyocyte fate determination focused primarily on genetic and chemical mediators of this process. However, increasing evidence suggests that mechanical interactions between the extracellular matrix (ECM) and cell surface receptors as well as physical interactions between neighboring cells play important roles in regulating the signaling pathways controlling the developmental processes of the heart. Interdisciplinary efforts have made it apparent that the influence of the ECM on cellular behavior occurs through a multitude of physical mechanisms, such as ECM boundary conditions, elasticity, and the propagation of mechanical signals to intracellular compartments, such as the nucleus. In addition to experimental studies, a number of mathematical models have been developed that attempt to capture the interplay between cells and their local microenvironment and the influence these interactions have on cellular self-assembly and functional behavior. Nevertheless, many questions remain unanswered concerning the mechanism through which physical interactions between cardiomyocytes and their environment are translated into biochemical cellular responses and how these signaling modalities can be utilized in vitro to fabricate myocardial tissue constructs from stem cell-derived cardiomyocytes that more faithfully represent their in vivo counterpart. These studies represent a broad effort to characterize biological form as a conduit for information transfer that spans the nanometer length scale of proteins to the meter length scale of the patient and may yield new insights into the contribution of mechanotransduction into heart development and disease.}, url = {https://doi.org/10.1007/s10237-012-0419-2}, author = {51 - and Sheehy SP and Grosberg A and Parker KK} } @article {1625824, title = {Controlling the contractile strength of engineered cardiac muscle by hierarchal tissue architecture}, journal = {Biomaterials}, volume = {33}, number = {23}, year = {2012}, pages = {5732-5741}, abstract = {The heart is a muscular organ with a wrapping, laminar structure embedded with neural and vascular networks, collagen fibrils, fibroblasts, and cardiac myocytes that facilitate contraction. We hypothesized that these non-muscle components may have functional benefit, serving as important structural alignment cues in inter- and intra-cellular organization of cardiac myocytes. Previous studies have demonstrated that alignment of engineered myocardium enhances calcium handling, but how this impacts actual force generation remains unclear. Quantitative assays are needed to determine the effect of alignment on contractile function and muscle physiology. To test this, micropatterned surfaces were used to build 2-dimensional myocardium from neonatal rat ventricular myocytes with distinct architectures: confluent isotropic (serving as the unaligned control), confluent anisotropic, and 20 μm spaced, parallel arrays of multicellular myocardial fibers. We combined image analysis of sarcomere orientation with muscular thin film contractile force assays in order to calculate the peak sarcomere-generated stress as a function of tissue architecture. Here we report that increasing peak systolic stress in engineered cardiac tissues corresponds with increasing sarcomere alignment. This change is larger than would be anticipated from enhanced calcium handling and increased uniaxial alignment alone. These results suggest that boundary conditions (heterogeneities) encoded in the extracellular space can regulate muscle tissue function, and that structural organization and cytoskeletal alignment are critically important for maximizing peak force generation.}, url = {https://doi.org/10.1016/j.biomaterials.2012.04.043}, author = {50 - and Feinberg AW and Alford PW and Jin H and Ripplinger CM and Werdich AA and Sheehy SP and Grosberg A and Parker KK} } @article {1625823, title = {Cooperative coupling of cell-matrix and cell-cell adhesions in cardiac muscle.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {109}, number = {25}, year = {2012}, pages = {9881-9886}, abstract = {Adhesion between cardiac myocytes is essential for the heart to function as an electromechanical syncytium. Although cell-matrix and cell{\textendash}cell adhesions reorganize during development and disease, the hierarchical cooperation between these subcellular structures is poorly understood. We reasoned that, during cardiac development, focal adhesions mechanically stabilize cells and tissues during myofibrillogenesis and intercalated disc assembly. As the intercalated disc matures, we postulated that focal adhesions disassemble as systolic stresses are transmitted intercellularly. Finally, we hypothesized that pathological remodeling of cardiac microenvironments induces excessive mechanical loading of intercalated discs, leading to assembly of stabilizing focal adhesions adjacent to the junction. To test our model, we engineered μtissues composed of two ventricular myocytes on deformable substrates of tunable elasticity to measure the dynamic organization and functional remodeling of myofibrils, focal adhesions, and intercalated discs as cooperative ensembles. Maturing μtissues increased systolic force while simultaneously developing into an electromechanical syncytium by disassembling focal adhesions at the cell{\textendash}cell interface and forming mature intercalated discs that transmitted the systolic load. We found that engineering the microenvironment to mimic fibrosis resulted in focal adhesion formation adjacent to the cell{\textendash}cell interface, suggesting that the intercalated disc required mechanical reinforcement. In these pathological microenvironments, μtissues exhibited further evidence of maladaptive remodeling, including lower work efficiency, longer contraction cycle duration, and weakened relationships between cytoskeletal organization and force generation. These results suggest that the cooperative balance between cell-matrix and cell{\textendash}cell adhesions in the heart is guided by an architectural and functional hierarchy established during development and disrupted during disease.}, url = {https://doi.org/10.1073/pnas.1203007109}, author = {49 - and McCain ML and Lee H and Aratyn-Schaus Y and Kl{\'e}ber AG and Parker KK} } @article {1625828, title = {Differential Contributions of Conformation Extension and Domain Unfolding to Properties of Fibronectin Nanotexiles}, journal = {Nano Letters}, volume = {12}, number = {11}, year = {2012}, pages = {5587-5592}, abstract = {Fibronectin (FN) textiles are built as nanometer-thick fabrics. When uniaxially loaded, these fabrics exhibit a distinct threshold between elastic and plastic deformation with increasing stretch. Fabric mechanics are modeled using an eight-chain network and two-state model, revealing that elastic properties of FN depend on conformational extension of the protein and that plastic deformation depends on domain unfolding. Our results suggest how the molecular architecture of a molecule can be exploited for designer mechanical properties of a bulk material.}, url = {https://doi.org/10.1021/nl302643g}, author = {48 - and Deravi LF and Su T and Paten JA and Ruberti JW and Bertoldi K and Parker KK} } @article {1625821, title = {Electrical Coupling and Propagation in Engineered Ventricular Myocardium With Heterogeneous Expression of Connexin43.}, journal = {111.259705Circulation Research}, volume = {110}, number = {11}, year = {2012}, pages = {1445-1453}, abstract = {Spatial heterogeneity in connexin (Cx) expression has been implicated in arrhythmogenesis.}, url = {https://doi.org/10.1161/circresaha.111.259705}, author = {47 - and Beauchamp P and Desplantez T and McCain ML and Li W and Asimaki A and Rigoli G and Parker KK and Saffitz JE and Kleber AG} } @article {1625819, title = {Modeling of cardiac muscle thin films: Pre-stretch, passive and active behavior.}, journal = {Journal of Biomechanics}, volume = {45}, number = {5}, year = {2012}, pages = {832-841}, abstract = {Recent progress in tissue engineering has made it possible to build contractile bio-hybrid materials that undergo conformational changes by growing a layer of cardiac muscle on elastic polymeric membranes. Further development of such muscular thin films for building actuators and powering devices requires exploring several design parameters, which include the alignment of the cardiac myocytes and the thickness/Young{\textquoteright}s modulus of elastomeric film. To more efficiently explore these design parameters, we propose a 3-D phenomenological constitutive model, which accounts for both the passive deformation including pre-stretch and the active behavior of the cardiomyocytes. The proposed 3-D constitutive model is implemented within a finite element framework, and can be used to improve the current design of bio-hybrid thin films and help developing bio-hybrid constructs capable of complex conformational changes.}, url = {https://dx.doi.org/10.1016\%2Fj.jbiomech.2011.11.024}, author = {46 - and Shim J and Grosberg A and Nawroth JC and Parker KK and Bertoldi K} } @article {1625822, title = {Muscle on a chip: In vitro contractility assays for smooth and striated muscle.}, journal = {Journal of Pharmacological and Toxicological Methods}, volume = {65}, number = {3}, year = {2012}, pages = {126-135}, abstract = {article i nfo Introduction: To evaluate the viability of a muscle tissue, it is essential to measure the tissue{\textquoteright}s contractile performance as well as to control its structure. Accurate contractility data can aid in development of more ef- fective and safer drugs. This can be accomplished with a robust in vitro contractility assay applicable to var- ious types of muscle tissue. Methods: The devices developed in this work were based on the muscular thin film (MTF) technology, in which an elastic film is manufactured with a 2D engineered muscle tissue on one side. The tissue template is made by patterning extracellular matrix with microcontact printing. When muscle cells are seeded on the film, they self-organize with respect to the geometric cues in the matrix to form a tissue. Results: Several assays based on the "MTF on a chip" technology are demonstrated. One such assay incorporates the contractility assay with striated muscle into a fluidic channel. Another assay platform in- corporates the MTFs in a multi-well plate, which is compatible with automated data collection and analysis. Fi- nally, we demonstrate the possibility of analyzing contractility of both striated and smooth muscle simultaneously on the same chip. Discussion: In this work, we assembled an ensemble of contractility assays for striated and smooth muscle based on muscular thin films. Our results suggest an improvement over current methods and an alternative to isolated tissue preparations. Our technology is amenable to both primary har- vests cells and cell lines, as well as both human and animal tissues.}, url = {http://dx.doi.org/10.1016/j.vascn.2012.04.001}, author = {45 - and Grosberg A and Nesmith AP and Goss JA and Brigham MD and McCain ML and Parker KK} } @article {1625829, title = {Myocyte shape regulates lateral registry of sarcomeres and contractility}, journal = {American Journal of Pathology}, volume = {101}, number = {6}, year = {2012}, pages = {2030-7}, abstract = {The heart actively remodels architecture in response to various physiological and pathological conditions. Gross structural change of the heart chambers is directly reflected at the cellular level by altering the morphological characteristics of individual cardiomyocytes. However, an understanding of the relationship between cardiomyocyte shape and the contractile function remains unclear. By using in vitro assays to analyze systolic stress of cardiomyocytes with controlled shape, we demonstrated that the characteristic morphological features of cardiomyocytes observed in a variety of pathophysiological conditions are correlated with mechanical performance. We found that cardiomyocyte contractility is optimized at the cell length/width ratio observed in normal hearts, and decreases in cardiomyocytes with morphological characteristics resembling those isolated from failing hearts. Quantitative analysis of sarcomeric architecture revealed that the change of contractility may arise from alteration of myofibrillar structure. Measurements of intracellular calcium in myocytes revealed unique characteristics of calcium metabolism as a function of myocyte shape. Our data suggest that cell shape is critical in determining contractile performance of single cardiomyocytes by regulating the intracellular structure and calcium handling ability.}, url = {https://doi.org/10.1016/j.ajpath.2012.08.045}, author = {44 - and Kuo P and Lee H and Bray MA and Geisse NA and Huang YT and Adams WJ and Sheehy SP and Parker KK} } @article {1625826, title = {A potential role for integrin signaling in mechanoelectrical feedback}, journal = {Progress in Biophysics \&Molecular Biology}, volume = {110}, number = {43864}, year = {2012}, pages = {196-203}, abstract = {Certain forms of heart disease involve gross morphological changes to the myocardium that alter its hemodynamic loading conditions. These changes can ultimately lead to the increased deposition of extracellular matrix (ECM) proteins, such as collagen and fibronectin, which together work to pathologically alter the myocardium{\textquoteright}s bulk tissue mechanics. In addition to changing the mechanical properties of the heart, this maladaptive remodeling gives rise to changes in myocardium electrical conductivity and synchrony since the tissue{\textquoteright}s mechanical properties are intimately tied to its electrical characteristics. This phenomenon, called mechanoelectrical coupling (MEC), can render individuals affected by heart disease arrhythmogenic and susceptible to Sudden Cardiac Death (SCD). The underlying mechanisms of MEC have been attributed to various processes, including the action of stretch activated channels and changes in troponin C-Ca(2+) binding affinity. However, changes in the heart post infarction or due to congenital myopathies are also accompanied by shifts in the expression of various molecular components of cardiomyocytes, including the mechanosensitive family of integrin proteins. As transmembrane proteins, integrins mechanically couple the ECM with the intracellular cytoskeleton and have been implicated in mediating ion homeostasis in various cell types, including neurons and smooth muscle. Given evidence of altered integrin expression in the setting of heart disease coupled with the associated increased risk for arrhythmia, we argue in this review that integrin signaling contributes to MEC. In light of the significant mortality associated with arrhythmia and SCD, close examination of all culpable mechanisms, including integrin-mediated MEC, is necessary.}, url = {https://doi.org/10.1016/j.pbiomolbio.2012.07.002}, author = {43 - and Dabiri BE and Lee H and Parker KK} } @article {1625825, title = {A tissue-engineered jellyfish with biomimetic propulsion}, journal = {Nature Biotechnology}, volume = {30}, number = {8}, year = {2012}, pages = {792-797}, abstract = {Reverse engineering of biological form and function requires hierarchical design over several orders of space and time. Recent advances in the mechanistic understanding of biosynthetic compound materials1,2,3, computer-aided design approaches in molecular synthetic biology4,5 and traditional soft robotics6,7, and increasing aptitude in generating structural and chemical microenvironments that promote cellular self-organization8,9,10 have enhanced the ability to recapitulate such hierarchical architecture in engineered biological systems. Here we combined these capabilities in a systematic design strategy to reverse engineer a muscular pump. We report the construction of a freely swimming jellyfish from chemically dissociated rat tissue and silicone polymer as a proof of concept. The constructs, termed {\textquoteright}medusoids{\textquoteright}, were designed with computer simulations and experiments to match key determinants of jellyfish propulsion and feeding performance by quantitatively mimicking structural design, stroke kinematics and animal-fluid interactions. The combination of the engineering design algorithm with quantitative benchmarks of physiological performance suggests that our strategy is broadly applicable to reverse engineering of muscular organs or simple life forms that pump to survive.}, url = {https://doi.org/10.1038/nbt.2269}, author = {42 - and Nawroth JC and Lee H and Feinberg AW and Ripplinger CM and McCain ML and Grosberg A and Dabiri JO and Parker KK} } @article {1625707, title = {Vascular smooth muscle contractility depends on cell shape}, journal = {Integrative Biology}, volume = {3}, number = {11}, year = {2011}, pages = {1063-1070}, abstract = {The physiologic role of smooth muscle structure in defining arterial function is poorly understood. We aimed to elucidate the relationship between vascular smooth muscle architecture and functional contractile output. Using microcontact printing and muscular thin film technology, we engineered in vitro vascular tissues with strictly defined geometries and tested their contractile function. In all tissues, vascular smooth muscle cells (VSMCs) were highly aligned with in vivo-like spindle architecture, and contracted physiologically in response to stimulation with endothelin-1. However, tissues wherein the VSMCs were forced into exaggerated spindle elongation exerted significantly greater contraction force per unit cross-sectional area than those with smaller aspect ratios. Moreover, this increased contraction did not occur in conjunction with an increase in traditionally measured contractile phenotype markers. These results suggest that cellular architecture within vascular tissues plays a significant role in conferring tissue function and that, in some systems, traditional phenotype characterization is not sufficient to define a functionally contractile population of VSMCs.}, url = {https://doi.org/10.1039/c1ib00061f}, author = {41 - and Patrick W. Alford and Alexander P. Nesmith and Johannes N. Seywerd and Anna Grosberg and Kevin Kit Parker} } @article {1625706, title = {Ensembles of engineered cardiac tissues for physiological and pharmacological study: Heart on a chip}, journal = {Miniaturisation for chemistry, physics, biology, materials science and bioengineering}, volume = {11}, number = {24}, year = {2011}, pages = {4165-73}, abstract = {Traditionally, muscle physiology experiments require multiple tissue samples to obtain morphometric, electrophysiological, and contractility data. Furthermore, these experiments are commonly completed one at a time on cover slips of single cells, isotropic monolayers, or in isolated muscle strips. In all of these cases, variability of the samples hinders quantitative comparisons among experimental groups. Here, we report the design of a {\textquoteleft}{\textquoteleft}heart on a chip{\textquoteright}{\textquoteright} that exploits muscular thin film technology {\textendash} biohybrid constructs of an engineered, anisotropic ventricular myocardium on an elastomeric thin film {\textendash} to measure contractility, combined with a quantification of action potential propagation, and cytoskeletal architecture in multiple tissues in the same experiment. We report techniques for real-time data collection and analysis during pharmacological intervention. The chip is an efficient means of measuring structure-function relationships in constructs that replicate the hierarchical tissue architectures of laminar cardiac muscle.}, url = {https://doi.org/10.1039/c1lc20557a}, author = {40 - and Anna Grosberg and Patrick W. Alford and Megan L. McCain and Kevin Kit Parker} } @article {1625795, title = {Blast-induced phenotypic switching in cerebral vasospasm}, journal = {Proceedings Of The National Academy Of Sciences Of The United States Of America}, volume = {108}, number = {31}, year = {2011}, pages = {12705-12710}, abstract = {Vasospasm of the cerebrovasculature is a common manifestation of blast-induced traumatic brain injury (bTBI) reported among combat casualties in the conflicts in Afghanistan and Iraq. Cerebral vasospasm occurs more frequently, and with earlier onset, in bTBI patients than in patients with other TBI injury modes, such as blunt force trauma. Though vasospasm is usually associated with the presence of subarachnoid hemorrhage (SAH), SAH is not required for vasospasm in bTBI, which suggests that the unique mechanics of blast injury could potentiate vasospasm onset, accounting for the increased incidence. Here, using theoretical and in vitro models, we show that a single rapid mechanical insult can induce vascular hypercontractility and remodeling, indicative of vasospasm initiation. We employed high-velocity stretching of engineered arterial lamellae to simulate the mechanical forces of a blast pulse on the vasculature. An hour after a simulated blast, injured tissues displayed altered intracellular calcium dynamics leading to hypersensitivity to contractile stimulus with endothelin-1. One day after simulated blast, tissues exhibited blast force dependent prolonged hypercontraction and vascular smooth muscle phenotype switching, indicative of remodeling. These results suggest that an acute, blast-like injury is sufficient to induce a hypercontraction-induced genetic switch that potentiates vascular remodeling, and cerebral vasospasm, in bTBI patients.}, url = {https://doi.org/10.1073/pnas.1105860108}, author = {39 - and Alford PW and Dabiri BE and Goss JA and Hemphill MA and Brigham MD and Parker KK} } @article {1625815, title = {Cyclic strain induces dual-mode endothelial-mesenchymal transformation of the cardiac valve}, journal = {Proceedings of the National Academy of Sciences}, volume = {108}, number = {50}, year = {2011}, pages = {19943-19948}, abstract = {Endothelial-mesenchymal transformation (EMT) is a critical event for the embryonic morphogenesis of cardiac valves. Inducers of EMT during valvulogenesis include VEGF, TGF-β1, and wnt/β-catenin (where wnt refers to the wingless-type mammary tumor virus integration site family of proteins), that are regulated in a spatiotemporal manner. EMT has also been observed in diseased, strain-overloaded valve leaflets, suggesting a regulatory role for mechanical strain. Although the preponderance of studies have focused on the role of soluble mitogens, we asked if the valve tissue microenvironment contributed to EMT. To recapitulate these microenvironments in a controlled, in vitro environment, we engineered 2D valve endothelium from sheep valve endothelial cells, using microcontact printing to mimic the regions of isotropy and anisotropy of the leaflet, and applied cyclic mechanical strain in an attempt to induce EMT. We measured EMT in response to both low (10\%) and high strain (20\%), where low-strain EMT occurred via increased TGF-β1 signaling and high strain via increased wnt/β-catenin signaling, suggesting dual strain-dependent routes to distinguish EMT in healthy versus diseased valve tissue. The effect was also directionally dependent, where cyclic strain applied orthogonal to axis of the engineered valve endothelium alignment resulted in severe disruption of cell microarchitecture and greater EMT. Once transformed, these tissues exhibited increased contractility in the presence of endothelin-1 and larger basal mechanical tone in a unique assay developed to measure the contractile tone of the engineered valve tissues. This finding is important, because it implies that the functional properties of the valve are sensitive to EMT. Our results suggest that cyclic mechanical strain regulates EMT in a strain magnitude and directionally dependent manner.}, url = {https://doi.org/10.1073/pnas.1106954108}, author = {38 - and Balachandran K and Alford PW and Wylie-Sears J and Goss JA and Grosberg A and Bischoff J and Aikawa E and Levine RA and Parker KK} } @article {1625816, title = {Ensembles of engineered cardiac tissues for physiological and pharmacological study: Heart on a chip.}, journal = {Lab Chip}, volume = {11}, number = {24}, year = {2011}, pages = {4165-4173}, abstract = {Traditionally, muscle physiology experiments require multiple tissue samples to obtain morphometric, electrophysiological, and contractility data. Furthermore, these experiments are commonly completed one at a time on cover slips of single cells, isotropic monolayers, or in isolated muscle strips. In all of these cases, variability of the samples hinders quantitative comparisons among experimental groups. Here, we report the design of a "heart on a chip" that exploits muscular thin film technology--biohybrid constructs of an engineered, anisotropic ventricular myocardium on an elastomeric thin film--to measure contractility, combined with a quantification of action potential propagation, and cytoskeletal architecture in multiple tissues in the same experiment. We report techniques for real-time data collection and analysis during pharmacological intervention. The chip is an efficient means of measuring structure-function relationships in constructs that replicate the hierarchical tissue architectures of laminar cardiac muscle.}, url = {https://doi.org/10.1039/c1lc20557a}, author = {37 - and Grosberg A and Alford PW and McCain ML and Parker KK} } @article {1625792, title = {Hierarchical architecture influences calcium dynamics in engineered cardiac muscle.}, journal = {Publisher}, volume = {236}, number = {3}, year = {2011}, pages = {366-373}, abstract = {Changes in myocyte cell shape and tissue structure are concurrent with changes in electromechanical function in both the developing and diseased heart. While the anisotropic architecture of cardiac tissue is known to influence the propagation of the action potential, the influence of tissue architecture and its potential role in regulating excitation-contraction coupling (ECC) are less well defined. We hypothesized that changes in the shape and the orientation of cardiac myocytes induced by spatial arrangement of the extracellular matrix (ECM) affects ECC. To test this hypothesis, we isolated and cultured neonatal rat ventricular cardiac myocytes on various micropatterns of fibronectin where they self-organized into tissues with varying degrees of anisotropy. We then measured the morphological features of these engineered myocardial tissues across several hierarchical dimensions by measuring cellular aspect ratio, myocyte area, nuclear density and the degree of cytoskeletal F-actin alignment. We found that when compared with isotropic tissues, anisotropic tissues have increased cellular aspect ratios, increased nuclear densities, decreased myocyte cell areas and smaller variances in actin alignment. To understand how tissue architecture influences cardiac function, we studied the role of anisotropy on intracellular calcium ([Ca(2+)](i)) dynamics by characterizing the [Ca(2+)](i)-frequency relationship of electrically paced tissues. When compared with isotropic tissues, anisotropic tissues displayed significant differences in [Ca(2+)](i) transients, decreased diastolic baseline [Ca(2+)](i) levels and greater [Ca(2+)](i) influx per cardiac cycle. These results suggest that ECM cues influence tissue structure at cellular and subcellular levels and regulate ECC.}, url = {https://doi.org/10.1258/ebm.2010.010239}, author = {36 - and Pong T and Adams WJ and Bray MA and Feinberg AW and Sheehy SP and Werdich AA and Parker KK} } @article {1625793, title = {Mechanotransduction: the role of mechanical stress, myocyte shape, and cytoskeletal architecture on cardiac function}, journal = {Pfl{\"u}gers Archiv - European Journal of Physiology}, volume = {462}, number = {1}, year = {2011}, pages = {89{\textendash}104}, abstract = {Mechanotransduction refers to the conversion of mechanical forces into biochemical or electrical signals that initiate structural and functional remodeling in cells and tissues. The heart is a kinetic organ whose form changes considerably during development and disease, requiring cardiac myocytes to be mechanically durable and capable of fusing a variety of environmental signals on different time scales. During physiological growth, myocytes adaptively remodel to mechanical loads. Pathological stimuli can induce maladaptive remodeling. In both of these conditions, the cytoskeleton plays a pivotal role in both sensing mechanical stress and mediating structural remodeling and functional responses within the myocyte.}, url = {https://doi.org/10.1007/s00424-011-0951-4}, author = {35 - and McCain ML and Parker KK} } @article {1625796, title = {Nanowired three-dimensional cardiac patches}, journal = {Nature Nanotechnology}, volume = {6}, number = {11}, year = {2011}, pages = {720-725}, abstract = {Engineered cardiac patches for treating damaged heart tissues after a heart attack are normally produced by seeding heart cells within three-dimensional porous biomaterial scaffolds1,2,3. These biomaterials, which are usually made of either biological polymers such as alginate4 or synthetic polymers such as poly(lactic acid) (PLA)5, help cells organize into functioning tissues, but poor conductivity of these materials limits the ability of the patch to contract strongly as a unit6. Here, we show that incorporating gold nanowires within alginate scaffolds can bridge the electrically resistant pore walls of alginate and improve electrical communication between adjacent cardiac cells. Tissues grown on these composite matrices were thicker and better aligned than those grown on pristine alginate and when electrically stimulated, the cells in these tissues contracted synchronously. Furthermore, higher levels of the proteins involved in muscle contraction and electrical coupling are detected in the composite matrices. It is expected that the integration of conducting nanowires within three-dimensional scaffolds may improve the therapeutic value of current cardiac patches.}, url = {https://doi.org/10.1038/nnano.2011.160}, author = {34 - and Dvir T and Timko BP and Brigham MD and Naik SR and Karajanagi SS and Levy O and Jin H and Parker KK} } @article {1625794, title = {A possible role for integrin signaling in diffuse axonal injury}, journal = {PLOS ONE}, volume = {6}, number = {7}, year = {2011}, pages = {e22899}, abstract = {Over the past decade, investigators have attempted to establish the pathophysiological mechanisms by which non-penetrating injuries damage the brain. Several studies have implicated either membrane poration or ion channel dysfunction pursuant to neuronal cell death as the primary mechanism of injury. We hypothesized that traumatic stimulation of integrins may be an important etiological contributor to mild Traumatic Brain Injury. In order to study the effects of forces at the cellular level, we utilized two hierarchical, in vitro systems to mimic traumatic injury to rat cortical neurons: a high velocity stretcher and a magnetic tweezer system. In one system, we controlled focal adhesion formation in neurons cultured on a stretchable substrate loaded with an abrupt, one dimensional strain. With the second system, we used magnetic tweezers to directly simulate the abrupt injury forces endured by a focal adhesion on the neurite. Both systems revealed variations in the rate and nature of neuronal injury as a function of focal adhesion density and direct integrin stimulation without membrane poration. Pharmacological inhibition of calpains did not mitigate the injury yet the inhibition of Rho-kinase immediately after injury reduced axonal injury. These data suggest that integrin-mediated activation of Rho may be a contributor to the diffuse axonal injury reported in mild Traumatic Brain Injury.}, url = {https://doi.org/10.1371/journal.pone.0022899}, author = {33 - and Hemphill MA and Dabiri BE and Gabriele S and Kerscher L and Franck C and Goss JA and Alford PW and Parker KK} } @article {1625817, title = {The Role of Mechanical Forces in Guiding Tissue Differentiation.}, journal = {Tissue Engineering in Regenerative Medicine}, year = {2011}, pages = {77-97}, abstract = {Stem cell differentiation is regulated by a diverse array of extracellular cues. Recent evidence suggests that mechanical interactions between extracellular matrix (ECM) and cell surface receptors as well as physical interactions between neighboring cells play important roles in stem cell self-renewal and differentiation. It is also becoming clear that the ECM effects cellular behavior through many physical mechanisms, such as ECM geometry, elasticity, and the propagation of mechanical signals to intracellular compartments. Considerable effort is being targeted at developing biomaterials that exploit cellular microenvironments in guiding cells to desired phenotypes and organizing these into functional tissues. Improved understanding of the interactions between stem cells and their physical environment should yield new insight into the mechanisms governing their activity and allow the fabrication of artificial ECM to promote tissue development.}, url = {http://dx.doi.org/10.1007/978-1-61779-322-6_5}, author = {32 - and Sheehy SP and Parker KK} } @article {1625791, title = {Self-organization of muscle cell structure and function.}, journal = {PLOS Computational Biology}, volume = {7}, number = {2}, year = {2011}, pages = {e1001088}, abstract = {The organization of muscle is the product of functional adaptation over several length scales spanning from the sarcomere to the muscle bundle. One possible strategy for solving this multiscale coupling problem is to physically constrain the muscle cells in microenvironments that potentiate the organization of their intracellular space. We hypothesized that boundary conditions in the extracellular space potentiate the organization of cytoskeletal scaffolds for directed sarcomeregenesis. We developed a quantitative model of how the cytoskeleton of neonatal rat ventricular myocytes organizes with respect to geometric cues in the extracellular matrix. Numerical results and in vitro assays to control myocyte shape indicated that distinct cytoskeletal architectures arise from two temporally-ordered, organizational processes: the interaction between actin fibers, premyofibrils and focal adhesions, as well as cooperative alignment and parallel bundling of nascent myofibrils. Our results suggest that a hierarchy of mechanisms regulate the self-organization of the contractile cytoskeleton and that a positive feedback loop is responsible for initiating the break in symmetry, potentiated by extracellular boundary conditions, is required to polarize the contractile cytoskeleton.}, url = {https://doi.org/10.1371/journal.pcbi.1001088}, author = {31 - and Grosberg A and Kuo P-L and Guo C-L and Geisse NA and Bray M-A and Adams WJ and Sheehy SP and Parker KK} } @article {1625814, title = {A simple model for nanofiber formation by rotary jet-spinning}, journal = {Applied Physics Letters}, volume = {99}, number = {20}, year = {2011}, pages = {203107}, abstract = {Nanofibers are microstructured materials that span a broad range of applications from tissue engineering scaffolds to polymer transistors. An efficient method of nanofiber production is rotary jet-spinning (RJS), consisting of a perforated reservoir rotating at high speeds along its axis of symmetry, which propels a liquid, polymeric jet out of the reservoir orifice that stretches, dries, and eventually solidifies to form nanoscale fibers. We report a minimal scaling framework complemented by a semi-analytic and numerical approach to characterize the regimes of nanofiber production, leading to a theoretical model for the fiber radius consistent with experimental observations. In addition to providing a mechanism for the formation of nanofibers, our study yields a phase diagram for the design of continuous nanofibers as a function of process parameters with implications for the morphological quality of fibers.}, url = {https://doi.org/10.1063/1.3662015}, author = {30 - and Mellado P and McIlwee HA and Badrossamay MR and Goss JA and Mahadevan L and Parker KK} } @article {1625797, title = {Vascular smooth muscle contractility depends on cell shape}, journal = {Integrative Biology}, volume = {3}, number = {11}, year = {2011}, pages = {1063-1070}, abstract = {The physiologic role of smooth muscle structure in defining arterial function is poorly understood. We aimed to elucidate the relationship between vascular smooth muscle architecture and functional contractile output. Using microcontact printing and muscular thin film technology, we engineered in vitro vascular tissues with strictly defined geometries and tested their contractile function. In all tissues, vascular smooth muscle cells (VSMCs) were highly aligned with in vivo-like spindle architecture, and contracted physiologically in response to stimulation with endothelin-1. However, tissues wherein the VSMCs were forced into exaggerated spindle elongation exerted significantly greater contraction force per unit cross-sectional area than those with smaller aspect ratios. Moreover, this increased contraction did not occur in conjunction with an increase in traditionally measured contractile phenotype markers. These results suggest that cellular architecture within vascular tissues plays a significant role in conferring tissue function and that, in some systems, traditional phenotype characterization is not sufficient to define a functionally contractile population of VSMCs.}, url = {https://doi.org/10.1039/c1ib00061f}, author = {29 - and Alford PW and Nesmith AP and Seywerd JN and Grosberg A and Parker KK} } @article {1625785, title = {Biohybrid thin films for measuring contractility in engineered cardiovascular muscle.}, journal = {Biomaterials}, volume = {31}, number = {13}, year = {2010}, pages = {3613-3621}, abstract = {In vitro cardiovascular disease models need to recapitulate tissue-scale function in order to provide in vivo relevance. We have developed a new method for measuring the contractility of engineered cardiovascular smooth and striated muscle in vitro during electrical and pharmacological stimulation. We present a growth theory-based finite elasticity analysis for calculating the contractile stresses of a 2D anisotropic muscle tissue cultured on a flexible synthetic polymer thin film. Cardiac muscle engineered with neonatal rat ventricular myocytes and paced at 0.5 Hz generated stresses of 9.2 +/- 3.5 kPa at peak systole, similar to measurements of the contractility of papillary muscle from adult rats. Vascular tissue engineered with human umbilical arterial smooth muscle cells maintained a basal contractile tone of 13.1 +/- 2.1 kPa and generated another 5.1 +/- 0.8 kPa when stimulated with endothelin-1. These data suggest that this method may be useful in assessing the efficacy and safety of pharmacological agents on cardiovascular tissue.}, url = {https://doi.org/10.1016/j.biomaterials.2010.01.079}, author = {28 - and Alford PW and Feinburn AW and Sheehy SP and Parker KK} } @article {1625790, title = {Hierarchical wrinkling patterns}, journal = {Soft Matter}, volume = {6}, number = {22}, year = {2010}, pages = {5751-5756}, abstract = {This paper reports a simple and flexible method for generating hierarchical patterns from wrinkling instability. Complex features with gradually changing topographies are generated by using the spontaneous wrinkling of a rigid membrane (titanium) on a soft foundation (polystyrene) compressed via the diffusion of a solvent. We show that the morphology of these unreported wrinkled patterns is directly related to the rheological properties of the polymer layer and the geometry of the diffusion front. Based on these ingredients, we rationalize the mechanism for the formation of hierarchical wrinkling patterns and quantify our experimental findings with a simple scaling theory. Finally, we illustrate the relevance of our structuration method by studying the mechanosensitivity of fibroblasts.}, url = {https://doi.org/10.1039/C0SM00394H}, author = {27 - and Vandeparre H and Gabriele S and Brau F and Gay C and Parker KK} } @article {1625789, title = {A multiscale model for eccentric and concentric cardiac growth through sarcomerogenesis}, journal = {Publisher}, volume = {265}, number = {3}, year = {2010}, pages = {433-442}, abstract = {We present a novel computational model for maladaptive cardiac growth in which kinematic changes of the cardiac chambers are attributed to alterations in cytoskeletal architecture and in cellular morphology. We adopt the concept of finite volume growth characterized through the multiplicative decomposition of the deformation gradient into an elastic part and a growth part. The functional form of its growth tensor is correlated to sarcomerogenesis, the creation and deposition of new sarcomere units. In response to chronic volume-overload, an increased diastolic wall strain leads to the addition of sarcomeres in series, resulting in a relative increase in cardiomyocyte length, associated with eccentric hypertrophy and ventricular dilation. In response to chronic pressure-overload, an increased systolic wall stress leads to the addition of sacromeres in parallel, resulting in a relative increase in myocyte cross sectional area, associated with concentric hypertrophy and ventricular wall thickening. The continuum equations for both forms of maladaptive growth are discretized in space using a nonlinear finite element approach, and discretized in time using the implicit Euler backward scheme. We explore a generic bi-ventricular heart model in response to volume- and pressure-overload to demonstrate how local changes in cellular morphology translate into global alterations in cardiac form and function.}, url = {https://doi.org/10.1016/j.jtbi.2010.04.023}, author = {26 - and G{\"o}ktepe S and Abilez OJ and Parker KK and Kuhl E} } @article {1625788, title = {Nuclear morphology and deformation in engineered cardiac myocytes and tissues.}, journal = {Biomaterials}, volume = {31}, number = {19}, year = {2010}, pages = {5143-5150}, abstract = {Cardiac tissue engineering requires finely-tuned manipulation of the extracellular matrix (ECM) microenvironment to optimize internal myocardial organization. The myocyte nucleus is mechanically connected to the cell membrane via cytoskeletal elements, making it a target for the cellular response to perturbation of the ECM. However, the role of ECM spatial configuration and myocyte shape on nuclear location and morphology is unknown. In this study, printed ECM proteins were used to configure the geometry of cultured neonatal rat ventricular myocytes. Engineered one- and two-dimensional tissue constructs and single myocyte islands were assayed using live fluorescence imaging to examine nuclear position, morphology and motion as a function of the imposed ECM geometry during diastolic relaxation and systolic contraction. Image analysis showed that anisotropic tissue constructs cultured on microfabricated ECM lines possessed a high degree of nuclear alignment similar to that found in vivo; nuclei in isotropic tissues were polymorphic in shape with an apparently random orientation. Nuclear eccentricity was also increased for the anisotropic tissues, suggesting that intracellular forces deform the nucleus as the cell is spatially confined. During systole, nuclei experienced increasing spatial confinement in magnitude and direction of displacement as tissue anisotropy increased, yielding anisotropic deformation. Thus, the nature of nuclear displacement and deformation during systole appears to rely on a combination of the passive myofibril spatial organization and the active stress fields induced by contraction. Such findings have implications in understanding the genomic consequences and functional response of cardiac myocytes to their ECM surroundings under conditions of disease.}, url = {https://doi.org/10.1016/j.biomaterials.2010.03.028}, author = {25 - and Bray MA and Adams WJ and Geisse NA and Feinberg AW and Sheehy SP and Parker KK} } @article {1625784, title = {Optimization of electroactive hydrogel actuators}, journal = {ACS Applied Materials \& Interfaces}, volume = {2}, number = {2}, year = {2010}, pages = {343-346}, abstract = {To improve actuation of hydrogels, we utilized an emulsion polymerization to engineer porous structures into polyelectrolyte hydrogels. Porous hydrogels generated large deformation as a result of enhanced deswelling mechanisms; for instance, the decreased number of COO- groups that must be protonated in porous hydrogels to initiate bending. Measurements of the mechanical properties revealed that porous hydrogels also bend to a larger extent because of their increased flexibility. Overall, our results demonstrate that the fast and large actuation of polyelectrolyte hydrogels can be accomplished by increasing the hydrogel porosity.}, url = {https://doi.org/10.1021/am900755w}, author = {24 - and O{\textquoteright}Grady M and Kuo P and Parker KK} } @article {1625786, title = {Surface-initiated assembly of protein nanofabrics}, journal = {Nanoletters}, volume = {10}, number = {6}, year = {2010}, pages = {2184-2191}, abstract = {Cells and tissues are self-organized within an extracellular matrix (ECM) composed of multifunctional, nano- to micrometer scale protein fibrils. We have developed a cell-free, surface-initiated assembly technique to rebuild this ECM structure in vitro. The matrix proteins fibronectin, laminin, fibrinogen, collagen type I, and collagen type IV are micropatterned onto thermosensitive surfaces as 1 to 10 nm thick, micrometer to centimeter wide networks, and released as flexible, free-standing nanofabrics. Independent control of microstructure and protein composition enables us to engineer the mechanical and chemical anisotropy. Fibronectin nanofabrics are highly extensible (\>4-fold) and serve as scaffolds for engineering synchronously contracting, cardiac muscle; demonstrating biofunctionality comparable to cell-generated ECM.}, url = {https://doi.org/10.1021/nl100998p}, author = {23 - and Feinberg AW and Parker KK} } @article {1625769, title = {Computational modeling of muscular thin films for cardiac repair}, journal = {Computational Mechanics}, volume = {4}, number = {43}, year = {2009}, pages = {535-544}, abstract = {Motivated by recent success in growing biohybrid material from engineered tissues on synthetic polymer films, we derive a computational simulation tool for muscular thin films in cardiac repair. In this model, the polydimethylsiloxane base layer is simulated in terms of microscopically motivated tetrahedral elements. Their behavior is characterized through a volumetric contribution and a chain contribution that explicitly accounts for the polymeric microstructure of networks of long chain molecules. Neonatal rat ventricular cardiomyocytes cultured on these polymeric films are modeled with actively contracting truss elements located on top of the sheet. The force stretch response of these trusses is motivated by the cardiomyocyte force generated during active contraction as suggested by the filament sliding theory. In contrast to existing phenomenological models, all material parameters of this novel model have a clear biophyisical interpretation. The predictive features of the model will be demonstrated through the simulation of muscular thin films. First, the set of parameters will be fitted for one particular experiment documented in the literature. This parameter set is then used to validate the model for various different experiments. Last, we give an outlook of how the proposed simulation tool could be used to virtually predict the response of multi-layered muscular thin films. These three-dimensional constructs show a tremendous regenerative potential in repair of damaged cardiac tissue. The ability to understand, tune and optimize their structural response is thus of great interest in cardiovascular tissue engineering.}, url = {https://ui.adsabs.harvard.edu/link_gateway/2009CompM..43..535B/doi:10.1007/s00466-008-0328-5}, author = {22 - and Bol M and Reese S and Parker KK and Kuhl K} } @article {1625771, title = {Control of myocyte remodeling in vitro with engineered substrates}, journal = {In Vitro Cellular \& Developmental biology. Animal.}, volume = {45}, number = {7}, year = {2009}, pages = {343-350}, abstract = {Tissue microenvironments can regulate cell behavior by imposing physical restrictions on their geometry and size. An example of these phenomena is cardiac morphogenesis, where morphometric changes in the heart are concurrent with changes in the size, shape, and cytoskeleton of ventricular myocytes. In this study, we asked how myocytes adapt their size, shape, and intracellular architecture when spatially confined in vitro. To answer this question, we used microcontact printing to physically constrain neonatal rat ventricular myocytes on fibronectin islands in culture. The myocytes spread and assumed the shape of the islands and reorganized their cytoskeleton in response to the geometric cues in the extracellular matrix. Cytoskeletal architecture is variable, where myocytes cultured on rectangular islands of lower aspect ratios (length to width ratio) were observed to assemble a multiaxial myofibrillar arrangement; myocytes cultured on rectangles of aspect ratios approaching those observed in vivo had a uniaxial orientation of their myofibrils. Using confocal and atomic force microscopy, we made precise measurements of myocyte volume over a range of cell shapes with approximately equal surface areas. When myocytes are cultured on islands of variable shape but the same surface area, their size is conserved despite the changes in cytoskeletal architecture. Our data suggest that the internal cytoskeletal architecture of the cell is dependent on extracellular boundary conditions while overall cell size is not, suggesting a growth control mechanism independent of the cytoskeleton and cell geometry.}, url = {https://doi.org/10.1007/s11626-009-9182-9}, author = {21 - and Geisse NA and Sheehy SP and Parker KK} } @article {1625783, title = {Generation of functional ventricular heart muscle from mouse ventricular progenitor Cells.}, journal = {Science}, volume = {326}, number = {5951}, year = {2009}, pages = {426-429}, abstract = {The mammalian heart is formed from distinct sets of first and second heart field (FHF and SHF, respectively) progenitors. Although multipotent progenitors have previously been shown to give rise to cardiomyocytes, smooth muscle, and endothelial cells, the mechanism governing the generation of large numbers of differentiated progeny remains poorly understood. We have employed a two-colored fluorescent reporter system to isolate FHF and SHF progenitors from developing mouse embryos and embryonic stem cells. Genome-wide profiling of coding and noncoding transcripts revealed distinct molecular signatures of these progenitor populations. We further identify a committed ventricular progenitor cell in the Islet 1 lineage that is capable of limited in vitro expansion, differentiation, and assembly into functional ventricular muscle tissue, representing a combination of tissue engineering and stem cell biology.}, url = {https://doi.org/10.1126/science.1177350}, author = {20 - and Domian IJ and Chiravuri M and van der Meer P and Feinberg AW and Shi X and Shao Y and Wu SM and Parker KK and Chien KR} } @article {1625770, title = {Time-warped comparison of gene expression in adaptive and maladaptive cardiac hypertrophy}, journal = {Publisher}, volume = {2}, number = {2}, year = {2009}, pages = {116-124}, abstract = {Background{\textemdash} Cardiac hypertrophy is classically regarded as a compensatory response, yet the active tissue remodeling processes triggered by various types of mechanical stress can enhance or diminish the function of the heart. Despite the disparity in outcomes, there are similarities in the hypertrophic responses. We hypothesized that a generic genetic response that is not dependent on the particular nature of the hypertrophic stimulus exists. To test our hypothesis, we compared the temporal evolution of transcriptomes measured in hearts subjected to either adaptive (exercise-induced) or maladaptive (aortic banding{\textendash}induced) hypertrophy.}, url = {https://doi.org/10.1161/CIRCGENETICS.108.806935}, author = {19 - and Sheehy SP and Huang S and Parker KK} } @article {1625768, title = {Cardiogenesis and the complex biology of regenerative cardiovascular medicine.}, journal = {Science}, volume = {322}, number = {5907}, year = {2008}, pages = {1494-1497}, abstract = {The heart is a complex organ system composed of a highly diverse set of muscle and nonmuscle cells. Understanding the pathways that drive the formation, migration, and assembly of these cells into the heart muscle tissue, the pacemaker and conduction system, and the coronary vasculature is a central problem in developmental biology. Efforts to unravel the biological complexity of in vivo cardiogenesis have identified a family of closely related multipotent cardiac progenitor cells. These progenitors must respond to non-cell-autonomous signaling cues to expand, differentiate, and ultimately integrate into the three-dimensional heart structures. Coupling tissue-engineering technologies with patient-specific cardiac progenitor biology holds great promise for the development of human cell models of human disease and may lay the foundation for novel approaches in regenerative cardiovascular medicine.}, url = {https://doi.org/10.1126/science.1163267}, author = {18 - and Chien KR and Domain IJ and Parker KK} } @article {1625757, title = {Dynamic control of protein-protein interactions}, journal = {Langmuir}, volume = {24}, number = {1}, year = {2008}, pages = {316-322}, abstract = {The capability to selectively and reversibly control protein-protein interactions in antibody-doped polypyrrole (PPy) was accomplished by changing the voltage applied to the polymer. Polypyrrole was doped with sulfate polyanions and monoclonal anti-human fibronectin antibodies (alphaFN). The ability to toggle the binding and dissociation of fibronectin (FN) to alphaFN-doped polypyrrole was demonstrated. Staircase potential electrochemical impedance spectroscopy (SPEIS) was performed to characterize the impedance and charge transfer characteristics of the alphaFN-doped PPy as a function of applied voltage, frequency, and FN concentration. Impedance measurements indicated oxidation of alphaFN-doped PPy promoted selective binding of FN to alphaFN antibodies and reduction of the polymer films facilitated FN dissociation. Moreover, SPEIS measurements suggested that the apparent reversibility of antigen binding to antibody-doped PPy is not due to the suppression of hydrophobic binding forces between antibody and antigen. Instead, our data indicate that reversible antigen binding to antibody-doped PPy can be attributed to the minimization of charge in the polymer films during oxidation and reduction. Furthermore, alphaFN-doped PPy was utilized to collect real-time, dynamic measurements of varying FN concentrations in solution by repeatedly binding and releasing FN. Our data demonstrate that antibody-doped PPy represents an electrically controllable sensing platform which can be exploited to collect rapid, repeated measurements of protein concentrations with molecular specificity.}, url = {https://doi.org/10.1021/la702041g}, author = {17 - and O{\textquoteright}Grady ML and Parker KK} } @article {1625758, title = {Micropatterning Approaches for Cardiac Biology}, journal = {Micro and Nanoengineering of the Cell Microenvironment: Technologies and Applications. Boston: Artech House.}, year = {2008}, pages = {341-357}, author = {16 - and Geisse NA and Feinberg AW and Kuo P and Sheehy S and Bray MA and Toner M}, editor = {Parker KK and Khademhosseini A} } @article {1625766, title = {Myofibrillar architecture in engineered cardiac myocytes}, journal = {Circulation Research}, volume = {103}, number = {4}, year = {2008}, pages = {340-342}, abstract = {Morphogenesis is often considered a function of transcriptional synchrony and the spatial limits of diffusing mitogens; however, physical constrainment by the cell microenvironment represents an additional mechanism for regulating self-assembly of subcellular structures. We asked whether myocyte shape is a distinct signal that potentiates the organization of myofibrillar arrays in cardiac muscle myocytes. We engineered the shape of neonatal rat ventricular myocytes by culturing them on microfabricated fibronectin islands, where they spread and assumed the shape of the island. Myofibrillogenesis followed, both spatially and temporally, the assembly of unique actin networks whose architecture was predictable given the shape of the island. Subsequently, the z lines of the sarcomeres aligned and registered in distinct patterns in different regions of the myocytes in such a way that orthogonal axes of contraction could be distinctly engineered. These data suggest that physical constrainment of muscle cells by extracellular matrix may be an important regulator of myofibrillar organization.}, url = {https://doi.org/10.1161/circresaha.108.182469}, author = {15 - and Parker KK and Tan J and Chen CS and Tung L} } @article {1625767, title = {Sarcomere alignment is regulated by myocyte shape}, journal = {Cell Motil Cytoskeleton}, volume = {65}, number = {issueNumber}, year = {2008}, pages = {641-651}, abstract = {Cardiac organogenesis and pathogenesis are both characterized by changes in myocyte shape, cytoskeletal architecture, and the extracellular matrix (ECM). However, the mechanisms by which the ECM influences myocyte shape and myofibrillar patterning are unknown. We hypothesized that geometric cues in the ECM align sarcomeres by directing the actin network orientation. To test our hypothesis, we cultured neonatal rat ventricular myocytes on islands of micro-patterned ECM to measure how they remodeled their cytoskeleton in response to extracellular cues. Myocytes spread and assumed the shape of circular and rectangular islands and reorganized their cytoskeletons and myofibrillar arrays with respect to the ECM boundary conditions. Circular myocytes did not assemble predictable actin networks nor organized sarcomere arrays. In contrast, myocytes cultured on rectangular ECM patterns with aspect ratios ranging from 1:1 to 7:1 aligned their sarcomeres in predictable and repeatable patterns based on highly localized focal adhesion complexes. Examination of averaged α-actinin images revealed invariant sarcomeric registration irrespective of myocyte aspect ratio. Since the sarcomere subunits possess a fixed length, this observation indicates that cytoskeleton configuration is length-limited by the extracellular boundary conditions. These results indicate that modification of the extracellular microenvironment induces dynamic reconfiguring of the myocyte shape and intracellular architecture. Furthermore, geometric boundaries such as corners induce localized myofibrillar anisotropy that becomes global as the myocyte aspect ratio increases.}, url = {https://dx.doi.org/10.1002\%2Fcm.20290}, author = {14 - and Bray MA and Sheehy SP and Parker KK} } @article {1625724, title = {Engineering design of a cardiac myocyte}, journal = {Journal of Computer-Aided Materials Design}, volume = {14}, number = {1}, year = {2007}, pages = {19-29}, abstract = {We describe a design algorithm to build a cardiac myocyte with specific spatial dimensions and physiological function. Using a computational model of a cardiac muscle cell, we modeled calcium (Ca2+) wave dynamics in a cardiac myocyte with controlled spatial dimensions. The modeled myocyte was replicated in vitro when primary neonate rat ventricular myocytes were cultured on micropatterned substrates. The myocytes remodel to conform to the two dimensional boundary conditions and assume the shape of the printed extracellular matrix island. Mechanical perturbation of the myocyte with an atomic force microscope results in calcium-induced calcium release from intracellular stores and the propagation of a Ca2+ wave, as indicated by high speed video microscopy using fluorescent indicators of intracellular Ca2+. Analysis and comparison of the measured wavefront dynamics with those simulated in the computer model reveal that the engineered myocyte behaves as predicted by the model. These results are important because they represent the use of computer modeling, computer-aided design, and physiological experiments to design and validate the performance of engineered cells. The ability to successfully engineer biological cells and tissues for assays or therapeutic implants will require design algorithms and tools for quality and regulatory assurance.}, url = {http://dx.doi.org/10.1007/s10820-006-9045-6}, author = {13 - and Adams WJ and Pong T and Geisse NA and Sheehy S and Parker KK} } @article {1625755, title = {Extracellular matrix, mechanotransduction and structural hierarchies in heart tissue engineering.}, journal = {Philosophical Transactions of the Royal Society B: Biological Sciences}, volume = {362}, number = {1484}, year = {2007}, pages = {1267-79}, abstract = {The spatial and temporal scales of cardiac organogenesis and pathogenesis make engineering of artificial heart tissue a daunting challenge. The temporal scales range from nanosecond conformational changes responsible for ion channel opening to fibrillation which occurs over seconds and can lead to death. Spatial scales range from nanometre pore sizes in membrane channels and gap junctions to the metre length scale of the whole cardiovascular system in a living patient. Synchrony over these scales requires a hierarchy of control mechanisms that are governed by a single common principle: integration of structure and function. To ensure that the function of ion channels and contraction of muscle cells lead to changes in heart chamber volume, an elegant choreography of metabolic, electrical and mechanical events are executed by protein networks composed of extracellular matrix, transmembrane integrin receptors and cytoskeleton which are functionally connected across all size scales. These structural control networks are mechanoresponsive, and they process mechanical and chemical signals in a massively parallel fashion, while also serving as a bidirectional circuit for information flow. This review explores how these hierarchical structural networks regulate the form and function of living cells and tissues, as well as how microfabrication techniques can be used to probe this structural control mechanism that maintains metabolic supply, electrical activation and mechanical pumping of heart muscle. Through this process, we delineate various design principles that may be useful for engineering artificial heart tissue in the future.}, url = {https://doi.org/10.1098/rstb.2007.2114}, author = {12 - and Parker KK and Ingber, Donald E} } @article {1625754, title = {Multidimensional detection and analysis of Ca2+ sparks in cardiac myocytes.}, journal = {Biophysical Journal}, volume = {92}, number = {12}, year = {2007}, pages = {4433-4443}, abstract = {Examining calcium spark morphology and its relationship to the structure of the cardiac myocyte offers a direct means of understanding excitation-contraction coupling mechanisms. Traditional confocal line scanning achieves excellent temporal spark resolution but at the cost of spatial information in the perpendicular dimension. To address this, we developed a methodology to identify and analyze sparks obtained via two-dimensional confocal or charge-coupled device microscopy. The technique consists of nonlinearly subtracting the background fluorescence, thresholding the data on the basis of noise level, and then localizing the spark peaks via a generalized extrema test, while taking care to detect and separate adjacent peaks. In this article, we describe the algorithm, compare its performance to a previously validated spark detection algorithm, and demonstrate it by applying it to both a synthetic replica and an experimental preparation of a two-dimensional isotropic myocyte monolayer exhibiting sparks during a calcium transient. We find that our multidimensional algorithm provides better sensitivity than the conventional method under conditions of temporally heterogeneous background fluorescence, and the inclusion of peak segmentation reduces false negative rates when spark density is high. Our algorithm is robust and can be effectively used with different imaging modalities and allows spark identification and quantification in subcellular, cellular, and tissue preparations.}, url = {https://doi.org/10.1529/biophysj.106.089359}, author = {11 - and Bray MA and Geisse NA and Parker KK} } @article {1625756, title = {Muscular thin films for building actuators and powering devices}, journal = {Science}, volume = {7}, number = {317}, year = {2007}, pages = {1366-1370}, abstract = {We demonstrate the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films. The constructs were built by culturing neonatal rat ventricular cardiomyocytes on polydimethylsiloxane thin films micropatterned with extracellular matrix proteins to promote spatially ordered, two-dimensional myogenesis. The constructs, termed muscular thin films, adopted functional, three-dimensional conformations when released from a thermally sensitive polymer substrate and were designed to perform biomimetic tasks by varying tissue architecture, thin-film shape, and electrical-pacing protocol. These centimeter-scale constructs perform functions as diverse as gripping, pumping, walking, and swimming with fine spatial and temporal control and generating specific forces as high as 4 millinewtons per square millimeter.}, url = {https://doi.org/10.1126/science.1146885}, author = {10 - and Feinberg AW and Feigel A and Shevkoplyas SS and Sheehy S and Whitesides GM and Parker KK} } @article {1625723, title = {Microtubules can bear enhanced compressive loads in living cells because of lateral reinforcement.}, journal = {Journal of Cell Biology}, volume = {173}, number = {5}, year = {2006}, pages = {733-741}, abstract = {Cytoskeletal microtubules have been proposed to influence cell shape and mechanics based on their ability to resist large-scale compressive forces exerted by the surrounding contractile cytoskeleton. Consistent with this, cytoplasmic microtubules are often highly curved and appear buckled because of compressive loads. However, the results of in vitro studies suggest that microtubules should buckle at much larger length scales, withstanding only exceedingly small compressive forces. This discrepancy calls into question the structural role of microtubules, and highlights our lack of quantitative knowledge of the magnitude of the forces they experience and can withstand in living cells. We show that intracellular microtubules do bear large-scale compressive loads from a variety of physiological forces, but their buckling wavelength is reduced significantly because of mechanical coupling to the surrounding elastic cytoskeleton. We quantitatively explain this behavior, and show that this coupling dramatically increases the compressive forces that microtubules can sustain, suggesting they can make a more significant structural contribution to the mechanical behavior of the cell than previously thought possible.}, url = {https://doi.org/10.1083/jcb.200601060}, author = {9 - and Clifford P. Brangwynne and Mackintosh, Frederick C. and Kumar, Sanjay and Nicholas A. Geisse and Jennifer Talbot and Mahadevan, L. and Kevin K. Parker and Donald E. Ingber and Weitz, DavidA.} } @article {1625722, title = {Symmetry-breaking in mammalian cell cohort migration during tissue pattern formation: role of random-walk persistence.}, journal = {Cell Motil Cytoskeleton}, volume = {6}, number = {61}, year = {2005}, pages = {201-213}, abstract = {Coordinated, cohort cell migration plays an important role in the morphogenesis of tissue patterns in metazoa. However, individual cells intrinsically move in a random walk-like fashion when studied in vitro. Hence, in the absence of an external orchestrating influence or template, the emergence of cohort cell migration must involve a symmetry-breaking event. To study this process, we used a novel experimental system in which multiple capillary endothelial cells exhibit spontaneous and robust cohort migration in the absence of chemical gradients when cultured on micrometer-scale extracellular matrix islands fabricated using microcontact printing. A computational model suggested that directional persistence of random-walk and dynamic mechanical coupling of adjacent cells are the critical control parameters for this symmetry-breaking behavior that is induced in spatially-constrained cell ensembles. The model predicted our finding that fibroblasts, which exhibit a much shorter motility persistence time than endothelial cells, failed to undergo symmetry breaking or produce cohort migration on the matrix islands. These findings suggest that cells have intrinsic motility characteristics that are tuned to match their role in tissue patterning. Our results underscore the importance of studying cell motility in the context of cell populations, and the need to address emergent features in multicellular organisms that arise not only from cell-cell and cell-matrix interactions, but also from properties that are intrinsic to individual cells.}, url = {https://doi.org/10.1002/cm.20077}, author = {8 - and Huang S and Brangwynne CP and Parker KK and Ingber} } @article {1625720, title = {Analytical model for predicting mechanotransduction effects in engineered cardiac tissue.}, journal = {Tissue Engineering}, volume = {9}, number = {2}, year = {2003}, pages = {283-289}, abstract = {Mechanochemical and mechanoelectrical signaling is imperative for cardiac organogenesis and underlies pathophysiological events. New techniques for engineering cardiac tissue allow unprecedented means of modeling these phenomena in vitro. However, experimental design is often hampered by a lack of models that can be adapted to the ideal conditions these methods allow. To address these deficiencies, we developed a mathematical model to calculate the distribution of stress and strain in fibrous cardiac tissue. The fluid-fiber-collagen model characterizes the mechanical behavior of cardiac tissue and is solved analytically for the distributions of stress and strain along the myocardial fibers. An example application of the model is presented: modeling the distribution of strains in the vicinity of an ischemic region. The ischemic region is stretched during systole, as has been shown in previous one-dimensional models. Our model predicts a complex distribution of stretch in the border zone surrounding the ischemic region and in nonischemic regions surrounding the border zone. These strain patterns may predict patterns of mechanochemical coupling that results in localized fibrosis, altered gene expression, or the mechanoelectrical signaling events that potentiate cardiac arrhythmias.}, url = {https://doi.org/10.1089/107632703764664747}, author = {7 - and Latimer DC and Roth BJ and Parker KK} } @article {1625716, title = {Cardiomyocyte cultures with controlled macroscopic anisotropy: a model for functional electrophysiological studies of cardiac muscle.}, journal = {Circulation Research}, volume = {99}, number = {12}, year = {2002}, pages = {e45-e54}, abstract = {Structural and functional cardiac anisotropy varies with the development, location, and pathophysiology in the heart. The goal of this study was to design a cell culture model system in which the degree, change in fiber direction, and discontinuity of anisotropy can be controlled over centimeter-size length scales. Neonatal rat ventricular myocytes were cultured on fibronectin on 20-mm diameter circular cover slips. Structure-function relationships were assessed using immunostaining and optical mapping. Cell culture on microabraded cover slips yielded cell elongation and coalignment in the direction of abrasion, and uniform, macroscopically continuous, elliptical propagation with point stimulation. Coarser microabrasion (wider and deeper abrasion grooves) increased longitudinal (23.5 to 37.2 cm/s; r=0.66) and decreased transverse conduction velocity (18.1 to 9.2 cm/s; r=-0.84), which resulted in increased longitudinal-to-transverse velocity anisotropy ratios (1.3 to 3.7, n=61). A thin transition zone between adjacent uniformly anisotropic areas with 45{\textdegree} or 90{\textdegree} difference in fiber orientation acted as a secondary source during 2{\texttimes} threshold field stimulus. Cell culture on cover slips micropatterned with 12- or 25-μm wide fibronectin lines and previously coated with decreasing concentrations of background fibronectin yielded transition from continuous to discontinuous anisotropic architecture with longitudinally oriented intercellular clefts, decreased transverse velocity (16.9 to 2.6 cm/s; r=-0.95), increased velocity anisotropy ratios (1.6 to 5.6, n=70), and decreased longitudinal velocity (36.4 to 14.6 cm/s; r=-0.85) for anisotropy ratios \>3.5. Cultures of cardiac myocytes with controlled degree, uniformity and continuity of structural, and functional anisotropy may enable systematic 2-dimensional in vitro studies of macroscopic structure-related mechanisms of reentrant arrhythmias. The full text of this article is available at http://www.circresaha.org.}, url = {https://doi.org/10.1161/01.RES.0000047530.88338.EB}, author = {6 - and Bursac N and Parker KK and Iravanian S and Tung L} } @article {1625715, title = {Directional control of lamellipodia extension by constraining cell shape and orienting cell tractional forces.}, journal = {Federation of American Societies for Experimental Biology (FASEB)}, volume = {16}, number = {10}, year = {2002}, pages = {1195-1204}, abstract = {Directed cell migration is critical for tissue morphogenesis and wound healing, but the mechanism of directional control is poorly understood. Here we show that the direction in which cells extend their leading edge can be controlled by constraining cell shape using micrometer-sized extracellular matrix (ECM) islands. When cultured on square ECM islands in the presence of motility factors, cells preferentially extended lamellipodia, filopodia, and microspikes from their corners. Square cells reoriented their stress fibers and focal adhesions so that tractional forces were concentrated in these corner regions. When cell tension was dissipated, lamellipodia extension ceased. Mechanical interactions between cells and ECM that modulate cytoskeletal tension may therefore play a key role in the control of directional cell motility.}, url = {https://doi.org/10.1096/fj.02-0038com}, author = {5 - and Kevin Kit Parker and Amy Lepre Brock and Cliff Brangwynne and Robert J Mannix and Wang, Ning and Emanuele Ostuni and Nicholas A Geisse and Josephine C Adams and George M. Whitesides and Ingber, Donald E} } @article {1625714, title = {The effects of tubulin-binding agents on stretch-induced ventricular arrhythmias.}, journal = {European Journal of Pharmacology}, volume = {417}, number = {1-2}, year = {2001}, pages = {131-40}, abstract = {Stretch-activated ion channels have been identified as transducers of mechanoelectric coupling in the heart, where they may play a role in arrhythmogenesis. The role of the cytoskeleton in ion channel control has been a topic of recent study and the transmission of mechanical stresses to stretch-activated channels by cytoskeletal attachment has been hypothesized. We studied the arrhythmogenic effects of stretch in 16 Langendorff-perfused rabbit hearts in which we pharmacologically manipulated the microtubular network of the cardiac myocytes. Group 1 (n=5) was treated with colchicine, which depolymerizes microtubules, and Group 2 (n=6) was treated with taxol, which polymerizes microtubules. Stretch-induced arrhythmias were produced by transiently increasing the volume of a fluid-filled left ventricular balloon with a volume pump driven by a computer-controlled stepper motor. Electrical events were recorded by a contact electrode which provided high-fidelity recordings of monophasic action potentials and stretch-induced depolarizations. The probability of eliciting a stretch-induced arrhythmia increased (0.22+/-0.11 to 0.62+/-0.19, p=0.001) in hearts treated with taxol (5 microM), whereas hearts treated with colchicine (100 microM) showed no statistically significant change. We conclude that proliferation of microtubules increased the arrhythmogenic effect of transient left ventricle diastolic stretch. This result indicates a possible mode of arrhythmogenesis in chemotherapeutic patients and patients exhibiting uncompensated ventricular hypertrophy. The data would indicate that the cytoskeleton represents a possible target for antiarrhythmic therapies.}, url = {https://doi.org/10.1016/s0014-2999(01)00856-1}, author = {4 - and Parker KK and Taylor LK and Atkinson JB and Hansen DE and Wikswo JP.} } @article {1625721, title = {Stretch-induced ventricular arrhythmias during acute ischemia and reperfusion.}, journal = {Journal of Applied Physiology}, volume = {97}, number = {1}, year = {2001}, pages = {377-383}, abstract = {Mechanical stretch has been demonstrated to have electrophysiological effects on cardiac muscle, including alteration of the probability of excitation, alteration of the action potential waveform, and stretch-induced arrhythmia (SIA). We demonstrate that regional ventricular ischemia due to coronary artery occlusion increases arrhythmogenic effects of transient diastolic stretch, whereas globally ischemic hearts showed no such increase. We tested our hypothesis that, during phase Ia ischemia, regionally ischemic hearts may be more susceptible to triggered arrhythmogenesis due to transient diastolic stretch. During the first 20 min of regional ischemia, the probability of eliciting a ventricular SIA (PSIA) by transient diastolic stretch increased significantly. However, after 30 min, PSIA decreased to a value comparable with baseline measurements, as expected during phase Ib, where most ventricular arrhythmias are of reentrant mechanisms. We also suggest that mechanoelectrical coupling may contribute to the nonreentrant mechanisms underlying reperfusion-induced arrhythmia. When coronary artery occlusion was relieved after 30 min of ischemia, we observed an increase in PSIA and the maintenance of this elevated level throughout 20 min of reperfusion. We conclude that mechanoelectrical coupling may underlie triggered arrhythmogenesis during phase 1a ischemia and reperfusion.}, url = {https://doi.org/10.1152/japplphysiol.01235.2001}, author = {3 - and Kevin Kit Parker and James A. Lavelle and L. Katherine Taylor and Zifa Wang and and David E. Hansen} } @article {1625713, title = {Symmetry breaking in cultured mammalian cells.}, journal = {In Vitro Cellular \& Developmental Biology - Animal}, volume = {36}, number = {9}, year = {2001}, pages = {563-565}, url = {https://doi.org/10.1007/bf02577523}, author = {2 - and Brangwynne, C. and Huang, S and Parker, K. K. and Ingber, D. E. and Ostuni, E} } @article {1625712, title = {A model of the magnetic fields created by single motor unit compound action potentials in skeletal muscle.}, journal = {IEEE Trans Biomed Eng.}, volume = {44}, number = {10}, year = {1997}, pages = {948-957}, abstract = {We have developed a computationally simple model for calculating the magnetic-field strength at a point due to a single motor unit compound action potential (SMUCAP). The motor unit is defined only in terms of its anatomical features, and the SMUCAP is approximated using the tripole model. The distributed current density J is calculated within the volume defined by the motor unit. The law of Biot and Savart can then be cast in a form necessitating that J be integrated only over the region containing current sources or conductivity boundaries. The magnetic-field strength is defined as the summation of the contributions to the field made by every muscle fiber in the motor unit. Applying this model to SMUCAP measurements obtained using a high-resolution SUper Conducting Quantum Interference Device (SQUID) magnetometer may yield information regarding the distribution of action currents (AC{\textquoteright}s) and the anatomical properties of single motor units within a muscle bundle.}, url = {https://doi.org/10.1109/10.634647}, author = {1 - and Parker KK and Wikswo JP Jr.} }