Effects of Substrate Mechanics on Contractility of Cardiomyocytes Generated from Human Pluripotent Stem Cells

Laurie B Hazeltine,Wendy C Crone,Beth L Pruitt,Wenqing Han,Xiaojun Lian,Mehmet G Badur,Chelsey S Simmons,Max R Salick,Tetsuro Wakatsuki,Sean P Palecek,Stephanie M Delgado

doi:10.1155/2012/508294

Abstract

Human pluripotent stem cell (hPSC-) derived cardiomyocytes have potential applications in drug discovery, toxicity testing, developmental studies, and regenerative medicine. Before these cells can be reliably utilized, characterization of their functionality is required to establish their similarity to native cardiomyocytes. We tracked fluorescent beads embedded in 4.4–99.7 kPa polyacrylamide hydrogels beneath contracting neonatal rat cardiomyocytes and cardiomyocytes generated from hPSCs via growth-factor-induced directed differentiation to measure contractile output in response to changes in substrate mechanics. Contraction stress was determined using traction force microscopy, and morphology was characterized by immunocytochemistry for α-actinin and subsequent image analysis. We found that contraction stress of all types of cardiomyocytes increased with substrate stiffness. This effect was not linked to beating rate or morphology. We demonstrated that hPSC-derived cardiomyocyte contractility responded appropriately to isoprenaline and remained stable in culture over a period of 2 months. This study demonstrates that hPSC-derived cardiomyocytes have appropriate functional responses to substrate stiffness and to a pharmaceutical agent, which motivates their use in further applications such as drug evaluation and cardiac therapies.

Highlights

Cardiovascular disease is the leading cause of mortality in the United States, resulting in 1 of every 2.9 deaths in 2006 [1]
This study demonstrates that Human pluripotent stem cell (hPSC-)derived cardiomyocytes have appropriate functional responses to substrate stiffness and to a pharmaceutical agent, which motivates their use in further applications such as drug evaluation and cardiac therapies
These results demonstrate that contraction stress of cardiomyocytes generated from Human pluripotent stem cells (hPSCs) increases with substrate stiffness

Summary

Introduction

Cardiovascular disease is the leading cause of mortality in the United States, resulting in 1 of every 2.9 deaths in 2006 [1]. The healthy heart linearly increases its contractile output in response to increased blood flow through a phenomenon known as the Frank-Starling Law [13]. Bead displacements can be resolved into cell tractions in a technique known as traction force microscopy [17] This method has been previously used to quantify contractility of quail, rat, and hESC-derived cardiomyocytes [18,19,20,21], but the physiological responses of hESC- and hiPSC-derived cardiomyocytes to changes in substrate mechanical properties have not yet been demonstrated. We hypothesized that hPSC-derived cardiomyocytes would increase their contractile output in response to increased substrate stiffness. We seeded neonatal rat and hPSC-derived cardiomyocytes onto PA hydrogels with a range of stiffnesses and measured their contraction stress using traction force microscopy. We examined changes in hPSC-derived cardiomyocyte contraction stress as a result of drug treatment and increased time in culture

Materials and Methods

Results

Discussion