Developing a FRET tension sensor-compatible system for analyzing cardiomyocyte tension alongside applied strain

Abstract

Cardiomyopathy refers to heart diseases in which myocardial tissue has undergone structural changes, often resulting in systolic dysfunction. Restructuring of the heart is influenced by mechanical forces and these organ-level changes are reflected by remodeling at the cellular level as well. Sarcomeres are the basic contractile unit of muscle tissues, and the direction in which they are added influences the shape of the cells and consequently the shape of the overall heart. Many existing cardiomyopathy therapies only address disease symptoms, such as reducing blood pressure with beta-blockers, but do not solve the underlying issue of systolic dysfunction. Current research focuses on genetic or biochemical methods, whereas manipulating the mechanics would allow for intervention upstream of those targets. Since mechanical forces such as tension strongly influence the development of various phenotypes, an alternative approach would be to leverage these mechanical interactions in the heart to specifically target cell remodeling. However, our current understanding of the relationship between tension and cellular remodeling is incomplete. Recent developments in the field have allowed for FRET force sensors to measure intracellular tension at focal adhesions, but are limited when it comes to externally applied forces. The goal of this project is to design a system capable of measuring intracellular tensile forces when applying an external strain, comprised of two parts. First, by culturing cardiomyocytes derived from a cell line expressing a FRET sensor line on a flexible substrate, it will be possible to image active tension forces experienced in the cell by applying a uniaxial strain. Secondly, the development of a free-standing cardiomyocyte monolayer “cell sheet” would allow for tension imaging of stretched cardiomyocytes alone without a support membrane. The system should allow for the study of how cells sense tension when an external force is applied and in what capacity.