Abstract 14803: Activin A Directly Impaired Human IPSC-cardiomyocyte Contractility and Electrophysiology

Abstract

Activin A is a homo-dimeric TGF-β family member involved in embryonic development, tissue morphogenesis, and cellular differentiation. Levels of activin A correlate with NYHA functional classification and age dependent cardiac dysfunction; however, no data are available to demonstrate a direct role for activin A in regulating human cardiomyocyte dysfunction. The purpose of this study was to characterize the functional impact of chronic activin A on human cardiomyocyte electrophysiology, contractility, calcium handling, and gene expression. Methods: Human iPSC-cardiomyocytes (iPSC-CM) were supplied by Fujifilm Cellular Dynamics. Calcium transients were captured using the FLIPR Tetra imager and impedance/electrophysiology by the Nanion CardioExcyte96. Cells were plated (50k/well), allowed to reach a stable synchronous monolayer, and dosed with 1nM of activin A (A) at each media change alongside a media control (C) or in the presence of inhibitory anti-activin A antibodies. Gene expression was determined using Taqman. Results: Activin A reduced contractile impedance amplitude (C=9.82±0.30, A=6.82±0.21 Ohms, p<0.01) and slowed relaxation velocity kinetics (C=48.78±2.65, A=35.07±1.07 Ohms/sec, p<0.01). Elongated extracellular field potential durations were observed with activin A treatment compared to control (C=0.49±0.02, A=0.56±0.01 sec, p<0.01). Impaired calcium handling peak amplitude (C=609±99, A= C=447±33 RFU, p<0.05) was also observed alongside slower calcium flux falling times (C=0.52±0.05, A=0.70±0.04 sec, p<0.01). An inhibitory activin-A antibody restored all parameters to control values. Chronic exposure of iPSC-CM to activin A reduced expression of calcium handling genes RYR2 (C=1.01±0.07, A=0.75±0.03, p<0.01) and ATP2A2 (C=1.00±0.05, A=0.89±0.05, p<0.05). Conclusions: Chronic activin A treatment reduced cardiomyocyte contractile amplitude, slowed contractile kinetics, impaired cardiomyocyte calcium handling, elongated the action potential, and reduced expression of genes regulating key calcium handling proteins. These data demonstrate that elevated levels of activin A can directly act on cardiomyocytes and therefore may contribute to cardiac dysfunction in heart failure and aged populations.