Characterization of hiPSC-derived cardiomyocytes formatted into a physiologically-relevant screening platform.
Current approaches on the study of acute cardiac toxicity and safety have been transformed with the availability of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Cardiac toxicity plays an important role in the failure of therapeutic agents in late stages of clinical trials, as well as in the removal of approved drugs from the market. The Comprehensive in vitro Proarrhythmia Assay (CiPA) constitutes a novel screening proposal intended to replace current regulatory strategies that have failed to predict the acute cardiotoxic effects of developing drugs. Through the CiPA initiative, researchers from diverse organizations such as the FDA, academic institutions, and pharmaceutical companies are evaluating hiPSC-CMs as an integral tool for the safety assessment of novel therapeutic compounds. Nonetheless, key challenges under consideration for the hiPSC-CM system are sub-ideal cardiomyocyte geometry, sub-cellular structural organization and overall electro physiological maturity. As an example, hiPSC-CMs frequently display, undefined or disarrayed sarcomeric organization when plated in standard cell cultureware. We have developed a novel high-density screening platform for hiPSC-CMs that is micro-engineered to emulate correct cardiac muscle fiber organization. This platform allows for passive self-alignment of hiPSC-CMs, leading to improved sarcomeric organization, as seen by readily identifiable, correctly patterned myofibrils along the cell body. Concomitantly, directionality of contraction of hiPSC-CM preparations were observed to be increased in this platform. We also observed increased gene expression of ryr2, atp2a2, and pln, key components of cardiomyocyte calcium handling pathways, which are crucial for cardiac physiology. The expression levels of cardiac ion channel genes such as cacnac1c, scn5a, kcne1, kcnq1 as well as cardiac cell junction components gja1, gja5 and dsp also showed an increase. Furthermore, a comprehensive analysis of calcium flux in hiPSC-CMs indicated that hiPSC-CM alignment in this platform influences cardiomyocyte physiology, which can be of great importance for the evaluation of compound cardiotoxicity. Altogether we describe a novel hiPSC-derived cardiomyocyte platform with greater physiological relevance that is pre-formatted to high throughput screening.