title: The Effect of Substrate Stiffness on Cardiomyocyte Action Potentials.
abstract: The stiffness of myocardial tissue changes significantly at birth and during neonatal development, concurrent with significant changes in contractile and electrical maturation of cardiomyocytes. Previous studies by our group have shown that cardiomyocytes generate maximum contractile force when cultured on a substrate with a stiffness approximating native cardiac tissue. However, effects of substrate stiffness on the electrophysiology and ion currents in cardiomyocytes have not been fully characterized. In this study, neonatal rat ventricular myocytes were cultured on the surface of flat polyacrylamide hydrogels with elastic moduli ranging from 1 to 25 kPa. Using whole-cell patch clamping, action potentials and L-type calcium currents were recorded. Cardiomyocytes cultured on hydrogels with a 9 kPa elastic modulus, similar to that of native myocardium, had the longest action potential duration. Additionally, the voltage at maximum calcium flux significantly decreased in cardiomyocytes on hydrogels with an elastic modulus higher than 9 kPa, and the mean inactivation voltage decreased with increasing stiffness. Interestingly, the expression of the L-type calcium channel subunit α gene and channel localization did not change with stiffness. Substrate stiffness significantly affects action potential length and calcium flux in cultured neonatal rat cardiomyocytes in a manner that may be unrelated to calcium channel expression. These results may explain functional differences in cardiomyocytes resulting from changes in the elastic modulus of the extracellular matrix, as observed during embryonic development, in ischemic regions of the heart after myocardial infarction, and during dilated cardiomyopathy.
authors.affiliation: Rice University Department of Bioengineering, Houston, TX, USA.
authors.forename: Sean D
authors.initials: SD
authors.lastname: Boothe
authors.affiliation: Rice University Department of Bioengineering, Houston, TX, USA.
authors.forename: Jackson D
authors.initials: JD
authors.lastname: Myers
authors.affiliation: Rice University Department of Bioengineering, Houston, TX, USA.|Texas Children's Hospital, Division of Congenital Heart Surgery, Houston, TX, USA.
authors.forename: Seokwon
authors.initials: S
authors.lastname: Pok
authors.affiliation: Texas Heart Institute/St. Luke's Hospital, Houston, TX, USA.
authors.forename: Junping
authors.initials: J
authors.lastname: Sun
authors.affiliation: Texas Heart Institute/St. Luke's Hospital, Houston, TX, USA.
authors.forename: Yutao
authors.initials: Y
authors.lastname: Xi
authors.affiliation: Texas Children's Hospital, Division of Congenital Heart Surgery, Houston, TX, USA.
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Nieto
authors.affiliation: Texas Heart Institute/St. Luke's Hospital, Houston, TX, USA.|Section of Cardiology, University of Texas School of Medicine at Houston, Houston, TX, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Rice University Department of Bioengineering, Houston, TX, USA. jeffrey.jacot@ucdenver.edu.|Texas Children's Hospital, Division of Congenital Heart Surgery, Houston, TX, USA. jeffrey.jacot@ucdenver.edu.
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Jacot
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D055119:Elastic Modulus; D020100:Hydrogels / Q000737:chemistry; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D013379:Substrate Specificity; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D002118:Calcium; D020746:Calcium Channels, L-Type; D020100:Hydrogels; D000099166:Polyacrylamides
keywords: Calcium channels, L-type; Cardiac electrophysiology; Cardiac myoblasts; Elastic modulus; Patch clamp; Rats