Safety pharmacology studies using EFP and impedance

Introduction: While extracellular field potential (EFP) recordings using multi-electrode arrays (MEAs) are a well-established technique for monitoring changes in cardiac and neuronal function, impedance is a relatively unexploited technology. The combination of EFP, impedance and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) has important implications for safety pharmacology as functional information about contraction and field potentials can be gleaned from human cardiomyocytes in a beating monolayer. The main objectives of this study were to demonstrate, using a range of different compounds, that drug effects on contraction and electrophysiology can be detected using a beating monolayer of hiPSC-CMs on the CardioExcyte 96.

Methods: hiPSC-CMs were grown as a monolayer on NSP-96 plates for the CardioExcyte 96 (Nanion Technologies) and recordings were made in combined EFP and impedance mode at physiological temperature. The effect of the hERG blockers, E4031 and dofetilide, hERG trafficking inhibitor, pentamidine, β-adrenergic receptor agonist, isoproterenol, and calcium channel blocker, nifedipine, was tested on the EFP and impedance signals.

Results: Combined impedance and EFP measurements were made from hiPSC-CMs using the CardioExcyte 96 (Nanion Technologies). E4031 and dofetilide, known to cause arrhythmia and Torsades de Pointes (TdP) in humans, decreased beat rate in impedance and EFP modes. Early afterdepolarization (EAD)-like events, an in vitro marker of TdP, could also be detected using this system. Isoproterenol and nifedipine caused an increase in beat rate. A long-term study (over 30h) of pentamidine, a hERG trafficking inhibitor, showed a concentration and time-dependent effect of pentamidine.

Discussion: In the light of the new Comprehensive in Vitro Proarrhythmia Assay (CiPA) initiative to improve guidelines and standardize assays and protocols, the use of EFP and impedance measurements from hiPSCs may become critical in determining the proarrhythmic risk of potential drug candidates. The combination of EFP offering information about cardiac electrophysiology, and impedance, providing information about contractility from the same area of a synchronously beating monolayer of human cardiomyocytes in a 96-well plate format has important implications for future cardiac safety testing.