Regulation of mechanical force on cardiomyocytes beating

Abstract

The mechanical behavior of cardiomyocytes plays an essential role in the maintenance of life and health. It is traditionally believed that both electrical and chemical signals modulate the cardiomyocytes behaviors. Recent discoveries have elucidated that the physical cues of microenvironment can regulate cell activities such as proliferation, spreading, migration, and differentiation. However, researches concerning the regulation of cardiomyocytes beating through mechanical force remains sparse. Here, we prepared different polyacrylamide gels coating with different cell adhesion ligand proteins to simulate the physical microenvironment of cardiomyocyte. Then the mechanical loading forces were loaded by employing a tungsten probe to stretch elastic hydrogels which can emulate the mechanical oscillations induced by the beating of adjacent cardiomyocytes. We investigated the responsive behavior of cardiomyocytes to external mechanical oscillations within various physical microenvironments. Firstly， we loaded 1 Hz mechanical oscillation on the matrix (E=11 kPa) with different kinds and concentrations of ligands (0, 5, 20, 100 μg/ml) to stimulate cardiomyocytes and observed it's mechanical response behavior. Our findings indicate that all kinds of ligands including Laminin, Fibronectin and Collagen I , can mediate the cardiomyocytes response to extrinsic mechanical oscillatory stimuli, which might be due to distinct mechanisms of mechanical force coupling (Fig.1b). This suggests that mechanical force signals can regulate the beating of cardiomyocytes through matrix-ligand-cell signaling pathway, thereby inducing intercellular coupled oscillations for rhythmic control of cardiomyocytes. Cardiomyoctes cultured on 20μg/ml Laminin show the highest and most stable response fraction. We hypothesized that there exist dual force transduction pathways for Laminin binding to integrin and dystrophin glycoprotein complex (DGC) (Fig.1a). We further analyzed the cardiomyocytes behaviors under mechanical oscillation with different substrate stiffness (E=1.8, 11, 27 kPa) and concentrations of Laminin (0, 5, 20, 100 μg/ml). We found that cardiomyoctes cultured on 1.8 kPa coated with 20 μg/ml Laminin show the highest response fraction (Fig.1c). Our results demonstrate that the stiffness of substrate, the type and density of cell adhesion ligands, as well as the strength and rhythm of the mechanical signals can synergetic influence the cardiomyocytes responses to external mechanical stimulations, which provides the foundation for understanding the diseases such as cardiac arrhythmias and heart failure following myocardial infarction.