Regulation of mechanical force on cardiomyocytes beating

Abstract

The mechanical behavior of cardiomyocytes plays an essential role in maintaining life and health. It is traditionally believed that both electrical signals 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, there is still limited research on regulating cardiomyocytes beating through mechanical force. Herein we prepare different polyacrylamide gels coated with different cell adhesion ligand proteins to simulate the physical microenvironment of cardiomyocytes. Then the mechanical loading forces are loaded by using a tungsten probe to stretch elastic hydrogels which can emulate the mechanical oscillations induced by the beating of adjacent cardiomyocytes. We investigate the responsive behavior of cardiomyocytes to external mechanical oscillations within various physical microenvironments. Firstly, we load 1 Hz mechanical oscillation on the matrix (<i>E</i> = 11 kPa) with different kinds and concentrations of ligands (0, 5, 20, 100 μg/mL) to stimulate cardiomyocytes and observe their 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. (b)). 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. Cardiomyocytes cultured on the matrix coated with 20 μg/mL Laminin show the highest and most stable response fraction. We hypothesize that there exist dual force transduction pathways for Laminin binding to integrin and dystrophin glycoprotein complex (DGC) (Fig. (a)). We further analyze the cardiomyocytes behaviors under mechanical oscillation with different values of substrate stiffness (<i>E</i> = 1.8, 11, 27 kPa) and concentrations of Laminin (0, 5, 20, 100 μg/mL). We find that cardiomyocytes cultured on 1.8 kPa coated with 20 μg/mL Laminin show the highest response fraction (Fig. (c)). 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 synergetically affect 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.