Human Cardiomyocytes Derived from Induced Pluripotent Stem Cells: High Throughput and High Content Assessment of Cardiac Toxicity and Drug Efficacy by Monitoring Cytosolic Free Calcium Transients
For high throughput screening (HTS) assays mainly recombinant cell lines expressing the target of interest are used due to the specificity, robustness, sensitivity, and the low costs of the assays. As is to be expected, these assays frequently lead to a high number of false positive hits. Complex physiological processes like the excitation-contraction coupling of cardiac myocytes and the efficacy of drugs or toxic drug action on such a system cannot be represented correctly with such simple cell models. Human iPSCM display a primary-like phenotype, reveal a regular spontaneous beating pattern and a functional calcium induced calcium release. Furthermore, these cells can be produced in large quantities in a quality controlled environment and are therefore an ideal model to be introduced into a standard calcium imaging HTS assay using Ca2+ sensitive fluorescent dyes in combination with a fluorescence plate reader system. The Hamamatsu FDSS kinetic plate readers are equipped with a high-speed camera, an integrated dispenser head and temperature control, allowing for detection of fast calcium signals under physiological temperatures. We have used cryopreserved hiPS-derived Cor.4U® cardiomyocytes in 384 well plates to optimise assay conditions and to detect changes in calcium transients induced by cardiac ion channel modulators. Using hiPS-derived Cor.4U® cardiomyocytes precultured for 3 - 5 days in 384 well plates, stable [Ca2±], signals were measured over 35 min and the effect of more than 30 compounds on [Ca21, transients in human iPS-derived cardiomyocytes were detected and analyzed.