Electrophysiological characterization of hiPSC-derived cardiomyocytes, including voltage-gated ion channels and action potential measurements, using automated patch clamp

The human-induced pluripotent stem-cell (hiPSC) technology was developed in 20071,2 and hiPSC-derived cardiomyocytes (hiPSC-CMs) have since then been recognized as a promising model system for cardiac drug screening and disease modelling3,4. Ion channels represent highly attractive therapeutic targets in the cardiovascular system, rendering electrophysiological studies of hiPSC-CMs important for their usage in drug discovery. However, such studies have traditionally been limited by the labor-intensive and low-throughput nature of patch-clamp electrophysiology. Here we use the automated patch clamp (APC) system QPatch II for high-throughput recordings of voltage-gated ion channels and paced action potentials in physiological solutions.
APC measurements of hiPSC-CMs are inherently challenging due to cell quality (batch-batch variation, differentiation efficiency)5, cardiac maturity (presence of pacemaker current If, and reduced hyperpolarizing current, IK1)6,7 and cell harvest (purity/quality of the single-cell suspension). Improving on all three parameters we were able to record cardiac voltage-gated currents (INa, ICa, IKr, IK1) with up to 50% success rates and paced action potentials with up to 20% success rates. The increased throughput of action potential measurements compared to manual patch clamp (10 cells per measurement plate) allowed us to measure dose-response effects of standard compounds such as nifedipine, E4031 and Bay K8466. In contrast to other APC systems, these measurements were performed in physiological solutions without the use of fluoride or other types of a seal-enhancer.