In vitro generated cardiomyocytes - a novel tool to assess the cardiotropic actions for drug development and safety pharmacology

Ralf Kettenhofen, Alexey Kuzmenkin, Huamin Liang, Silke Schwengberg, Jürgen Hescheler, Heribert Bohlen
1Axiogenesis AG, Cologne, Germany, 2Institute for Neurophysiology, University of Cologne, Cologne, Germany

Scientists in cardiac science and toxicology suffer from the lack of standardised, pure in vitro cardiac cell and tissue models. Up-to-date, models for cardiotoxicity comprise recombinant cell systems e.g. injected oocytes and mammalian cell lines expressing ion channels or primary preparations of cardiomyocytes, cardiac tissues (e.g. papillary muscle) and Langendorff-perfused explanted hearts or in vivo animal models, respectively. Here we present data that in vitro generated, fibroblast-free cardiomyocytes derived murine embryonic stem cells (mESC-CM – Cor.At®) can be produced in large-scale and are a novel pure in vitro model to solve critical issues of cardiac ion channel modulation and humoral regulation. mESC-CM keep their functional integrity in culture for weeks after thawing. Voltage clamp experiments revealed expression of typical cardiac currents like INa, ICa,L, and IK. Block of IKr currents by E-4031(hERG) was demonstrated in current and voltage clamp experiments and extra-cellular recording from multi electrode arrays (MEAs) revealing the capability of the mES-CM as an in vitro model for non-clinical assessment of the potential for delayed cardiac repolarisation. Application of typical ion channel blockers lidocaine (INa blocker) and nifedipine (ICa,L blocker) as well as the beta-adrenergic and muscarinic agonists suprarenin and carbachol, respectively, in voltage clamp and MEA experiments display the functional integrity of the cells. Due to their electrical coupling evidenced by synchronous beating in 2D tissue cultures on MEAs and the expression of Cx43, the mESC-CM represent the first standardised in vitro cardiac tissue model to assess drug-induced arrhythmias. Furthermore, we were able to demonstrate cardiomyocyte specific cytotoxicity and the induction of hypertrophy.