Using automated patch clamp for high throughput pharmacological characterization of cardiac action potential in human induced pluripotent stem cell derived cardiomyocytes
ISSCR Annual Meeting 2023, Boston, US
The human induced pluripotent stem-cell (hiPSC) technology was developed in 2007 1,2 and hiPSC-derived cardiomyocytes (hiPSC-CMs) 3 have since then been recognized as a promising model system for cardiac drug screening and disease modelling 4,5. Ion channels represent highly attractive therapeutic targets in the cardiovascular system, rendering electrophysiological studies of hiPSC-CMs important for their usage in drug discovery and safety pharmacology. However, the low diastolic resting potential, low throughput, and the tediousness of the gold standard; manual patch clamp measurements, has limited their applicability in drug discovery projects.
To address these limitations, we have developed an assay to measure voltage gated current and evoked action potentials using our automated patch clamp (APC) system the QPatchII. Cellular electrophysiology on hiPSC-CMs is inherently challenging due to cell quality (batch-batch variation, differentiation efficiency) cardiac maturity (presence of pacemaker current If , and reduced hyperpolarizing current, IK1) 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 and ICa) and paced action potentials. To address the native depolarized resting membrane potential of hiPSC-CMs 6 , we have introduced a feature called Adaptive Current Clamp – or IAdapt – on our APC systems which allows users to automatically clamp each individual hiPSC-CM to the holding potential of interest and evoke a cardiac action potential with duration and amplitude well mirroring the human adult cardiac action potential.
We obtained an increased throughput and significant improvement of the action potential parameters including resting membrane potential, upstroke velocity and action potential duration with the use of the IAdapt feature. This allowed us to observe the effect of two generic drugs, BayK8644 and Nifidipine, on the action potential duration. In contrast to other APC systems these measurements were performed in physiological solutions without the use of fluoride or other types of seal-enhancers.