Automated Action Potential Recording in Stem Cell-Derived Cardiomyocytes for Proarrhythmia Assessment

Abstract

Development of in vitro toxicity assays based on the human stem cell-derived cardiomyocytes (SC-CMs) provides an opportunity to assess the specific cardiac safety end-points early in drug development. The cardiac action potential (AP) is an established biomarker for cardiac safety and efficacy in humans and a good detector of proarrhythmic events. However, its utility has been mainly limited by a low throughput of manual patch clamp and a restricted access to healthy human cardiomyocytes. The recent progress in automated electrophysiology combined with availability of human SC-CMs provides an exciting possibility to measure AP in human cells expressing endogenous cardiac ion channels.Electrophysiological properties of human SC-CMs were investigated with special focus on establishment of automated cell-based cardiac safety screens.For the first time assay protocols and procedures were established to measure and characterize both cardiac AP and the main underlying currents in human SC-CMs using automated electrophysiology platforms Patchliner(r) and Synchropatch(r)96 (Nanion Technologies GmbH). Employment of the higher throughput systems allowed capturing and evaluating AP and cardiac current profiles in cardiomyocyte cultures revealing specific heterogeneity. Outward potassium current mainly consisting of slow and rapid delayed rectifier and Ca2+-activated components as well as inward cardiac sodium current were recorded and characterized. Density of L-type Ca2+ current varied with the type and differentiation status of cardiomyocytes. The inward rectifier potassium current and a pacemaker current could also be measured. These results demonstrate that functional cardiac currents and appropriate AP present in human SC-CMs can be successfully recorded by automated electrophysiology systems.The automated cardiac AP measurements in human SC-CMs exemplify a novel screening method for early and sensitive detection of multiple ion channel effects in vitro completing the current core battery hERG assay and animal ECG measurements in pre-clinical safety assessment.