About the Lab

The Disease Biophysics Group (DBG) at Harvard University is an interdisciplinary team of biologists, physicists, engineers and material scientists actively researching the structure/function relationship in cardiac, neural, and vascular smooth muscle tissue engineering. We seek to quantify cellular mechanotransduction at the single-cell and tissue level to understand the effect on electrophysiology and disease states.

Cardiac Research

Our group’s primary research focus is on understanding cellular mechanotransduction in the heart. Specifically, we are interested in how extracellular matrix and cytoskeletal architecture potentiate and modulate the activation of mechanochemical and mechanoelectrical signaling pathways and genetic programs in cardiac cells and tissues. In order to study these mechanisms at different spatial scales, we use cellular and tissue engineering techniques that allow us to build custom-designed cardiac myocytes and ventricular tissue constructs as experimental preparations.

Why are we interested in this problem of biological scaling in the heart?

The Cardiac Arrhythmia Suppression Trial (CAST) of the late 1980’s was a clinical trial designed to test the hypothesis that suppression of premature ventricular contractions (PVC) with Class I antiarrhythmics (blockers of excitatory sodium currents) would reduce arrhythmic death risk. The trial was ended prematurely by the FDA when the mortality rate of those patients on encainide and flecainide, the Class I drugs studied, nearly quadrupled the mortality rates of those patients on placebo. Subsequent studies of antiarrhythmic drugs indicate that drugs that alter ion channel kinetics often show little or no benefit in the suppression of ventricular tachycardia and ventricular fibrillation. To date, there is no clinically reliable means of treating cardiac arrhythmias medicinally.

How are we approaching this problem?

We hypothesize that single channel blockade antiarrhythmic strategies were inherently flawed because they target a single scale (molecular level) without considering the fact that the pathogenesis of arrhythmias transcends multiple levels of integration, i.e., it is a multiscale problem. We propose that increasing the spatial scale of the drug target search, from single proteins to protein networks, will result in the development of more effective antiarrhythmic medicinal therapies. Thus, we take a multiscale approach, by targeting several spatial magnitudes simultaneously. At the length scale of a single cell, we study the cytoskeletal networks that span the entirety of the cardiac myocyte and modulate the kinetics of many of the more than half dozen ion channels that contribute to the cardiac action potential. More specifically, we investigate 1) how the cardiac myocyte cytoskeleton self-assembles; and, 2) the role of cytoskeletal architecture modulating action potential morphology and calcium metabolism. In tissue-scale studies, we investigate cell ensembles and correlate their behavior to larger tissue and whole heart function. Cell-cell mechanocoupling, via cell adhesion proteins and extracellular matrix, undoubtedly contributes to the electrical synchrony amongst cardiac myocytes. Here, more specific studies are directed towards investigating how the mechanical continuity amongst cardiac myocytes modulates electrical excitability and may contribute to the wavebreaks that mark the transition from ventricular tachycardia to ventricular fibrillation.

Immunofluorescence Staining of Micropatterned Cardiac Myocytes

FIGURE: Microcontact Printing used to control Cardiomyocyte geometry and cellular architecture. For all Images: Sarcomeric actin labeled in green, sarcomeric alpha-actinin (Z-lines) marked in red, nucleus marked in blue.
A: Adult Rat Cardiac Myocyte without structural modification (nucleus not shown).
B: Neonatal Rat Cardiac Myocyte without structural modification, cultured on a monolayer of extracellular matrix protein.
C: Neonatal Rat Cardiac Myocyte cultured on a rectangular island of extracellular matrix protein.
D: Neonatal Rat Cardiac Myocyte cultured on a triangular island of extracellular matrix protein.
E: Neonatal Rat Cardiac Myocyte cultured on a square island of extracellular matrix protein.
F: Neonatal Rat Cardiac Myocyte cultured on a circular island of extracellular matrix protein.

Detection, Characterization and Visualization of Calcium Sparks In Micropatterned Cardiac Myocytes
Primary Investigator: Mark Bray, Ph.D.

The cytoarchitecture of the myocyte has been determined to be critical in understanding not only mechanical contraction of the cell but also electrical propagation. Knowledge of this mechanotransduction mechanism has implications in the treatment of stretch-activated arrhythmias, as well as understanding the role of the extracellular environment on intracellular signaling pathways. Our objective is to micropattern myocytes into various shapes and examine spark occurrence as a function of cell shape. The expectation is that cell shapes which incorporate regions of high mechanical cellular stress will modulate calcium spark characteristics as the cytoskeleton reconfigures itself accordingly. A critical and novel component of this project is the development of software able to detect and visualize sparks in two-dimensions.

FIGURE: Fluorescence map of square cell (top left) and with background fluorescence subtracted (bottom left). Visualization of spark boundaries with respect to (x,y,t), shown in red (right).

Visualization of Calcium Sparks in Cardiac Myocytes

Estimation of Contractile Stress on Cardiac Myocytes
Primary Investigator: Poling Kuo, M.D.

We hypothesize that mechanical coupling between cells plays a critical role both in the normal and pathological development of cardiac tissues. We are using traction force microscopy to map the contractile stresses of micropatterned neonatal rat cardiomyocytes.

FIGURE: Relative stress field of cardiac myocytes exhibited by red vectors. The bottom black scale bar represents 10 um.

Analysis of Traction Forces In Contractile Cardiac Myocytes
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What's New

DBG Lab is Operational! March 15th, 2021

After 17 years of outstanding science in Cambridge, the DBG has moved to the Engineering School’s new campus in Allston. As of March 2, the lab is fully operational and has resumed experiments. Thank you to all alumni and current personnel for constantly raising the bar. Stand by for the next chapter of DBG science!

Congratulations to Dr. Megan McCain! March 10th, 2021

Our congratulations go out to DBG alumna, Dr. Megan McCain, who has recently received tenure at University of Southern California!

Farewell to Dr. Suhwan Kim! January 13th, 2021

Congratulations to Dr. Suhwan Kim, who has accepted a position as an Assistant Professor in the Department of Chemical Engineering at Dong-A University in Basun, South Korea! Dr. Kim was an integral part of our brain team for over a year as a postdoctoral fellow. We wish him the best on this next step in his career!

Inaugural Issue — Biophysics Reviews! January 4th, 2021

Dr. Kevin Kit Parker launched Biophysics Reviews, a new peer-reviewed journal for the biophysics research community on December 14. Produced by scientific publisher AIP Publishing, the aims to expand “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”.

References:
1. KK Parker, L Longobardi, A Sulicz. “Welcome to Biophysics Reviews, a big tent for the biophysics community”. Biophysics Reviews. 14 Dec 2020; 1(1); 010401. https://doi.org/10.1063/5.0036408.

A Belated Farewell and Congratulations to Dr. Ardoña! October 14th, 2020

Congratulations to Dr. Herdeline Ardoña, who has accepted a position as an Assistant Professor in the University of California Irvine Department of Chemical and Biomolecular Engineering. She joined the Disease Biophysics Group as a postdoctoral fellow in 2017 and was an essential part of our research and mentoring team. Best of luck to you as you settle in and get your research group up and running!