Analyzing atrial human iPSC-cardiomyocyte responses to GPCR and ion channel modulators: Introducing a chamber-specific cell model for preclinical testing

Abstract

Over the past decade, commercial human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have emerged as vital tools for preclinical cardiac risk assessment, thanks to their human origin and limitless reproducibility. Commonly, mixed cell populations comprising ventricular, atrial, and nodal cardiomyocytes are used. However, diseases such as atrial fibrillation, impacting over 33 million individuals globally, underscore the urgent need for cardiac subtype-specific commercial cell lines. Here, we characterize commercially available hiPSC-derived atrial cardiomyocytes (atrial hiPSC-CMs) and compare them to hiPSC-derived ventricular cardiomyocytes (ventricular hiPSC-CMS) (both Axol Biosciences) regarding their contractile properties using FLEXcyte 96 technology. The cells were seeded on flexible 96-well plates mimicking physiological human heart conditions in vitro. Pre-compound beat characteristics were analyzed regarding beat rate and amplitude. Compound-induced effects of GPCR agonists acetylcholine and carbachol were tested regarding contractile properties including beat rate, amplitude and beat duration using a concentration range of 1 μM – 100 μM. Furthermore, ion channel modulators including S-Bay K8644, ivabradine, vernakalant and 4-Aminopyridine were assessed at 4 different concentrations ranging from 100 nM – 1 μM. Pre-compound analysis reveals cell type-specific beat shapes analogous to the respective cardiac action potential, in which atrial cells show a higher beat rate and less pronounced contraction force compared to ventricular cells. Pharmacological analysis demonstrates a higher susceptibility of atrial hiPSC-CMs towards GPCR agonists acetylcholine and carbachol than ventricular cells. Ion channel modulator S-Bay K8644 induces reversed inotropic and chronotropic effects in atrial and ventricular cells, while ivabradine causes a pronounced negative chronotropic effect in atrial cells alone. 4-Aminopyridine reveals prolonged contraction duration and reduced chronotropy in atrial hiPSC-CMs, while vernakalant induces opposing reactions in chronotropy of chamber-specific cardiomyocytes. These results underscore the significant pharmacological responses of atrial hiPSC-CMs and their utility on a multiwell contractility platform for enhancing in vitro cardiac liability studies and disease modeling.