Abstract 306: Engineered Neonatal Rat Cardiac Tissue Models Immature in vivo Myocardium

Abstract

Correlating contractile function, cellular, and molecular events in the immature heart is hampered by the limited availability of easily studied models. 2D cultures provide molecular data but can not replicate in vivo mechanical events. Isolated perfused hearts provide contractile data, but gene expression manipulation and molecular studies are limited. Here we demonstrate the utility of a 3D neonatal cardiomyocyte culture to model immature native myocardium. Isolated cardiomyocytes from day-old Sprague-Dawley rat pups were mixed with collagen and matrigel, and cast into cylindrical constructs (termed NECT). After seven days in culture NECT force-strain, force-frequency, and calcium transient data were collected. Identical data were collected from aged matched intact papillary muscle. RNA and protein were isolated from NECT and papillary muscle to assess sarcomeric proteins and quantitate developmentally regulated gene expression. Transcription of β-actin and cardiac α-actin were lower in NECT vs. native ( P <0.001; N=8). Myosin heavy chain α and β isoform ratios and content were similar between NECT and native while metabolic genes GLUT1 and MCAD were increased, and GLUT4 and PDK4 decreased ( P < .05) . Major sarcomeric proteins were well represented in NECT while regulatory proteins MyBPC and TnI were decreased. Peak developed force and calcium transients were similar between NECT and native, while the rate of force development and relaxation were accelerated in the NECT (Table ). 3D culture of neonatal cardiomyocytes, NECT, replicates important structural and functional features of immature native myocardium. The in vitro investigation of 3D NECT represents a unique opportunity to study electromechanical, metabolic, and endocrine factors that influence myocardial maturation. This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia). Comparison of Force and Calcium Transients in NECT