Characterization of Human-Induced Pluripotent Stem Cell–Derived Cardiomyocytes: Bioenergetics and Utilization in Safety Screening

Abstract

Cardiotoxicity remains the number one reason for drug withdrawal from the market, and Food and Drug Administration issued black box warnings, thus demonstrating the need for more predictive preclinical safety screening, especially early in the drug discovery process when much chemical substrate is available. Whereas human-ether-a-go-go related gene screening has become routine to mitigate proarrhythmic risk, the development of in vitro assays predicting additional on- and off-target biochemical toxicities will benefit from cellular models exhibiting true cardiomyocyte characteristics such as native tissue-like mitochondrial activity. Human stem cell-derived tissue cells may provide such a model. This hypothesis was tested using a combination of flux analysis, gene and protein expression, and toxicity-profiling techniques to characterize mitochondrial function in induced pluripotent stem cell (iPSC) derived human cardiomyocytes in the presence of differing carbon sources over extended periods in cell culture. Functional analyses demonstrate that iPSC-derived cardiomyocytes are (1) capable of utilizing anaerobic or aerobic respiration depending upon the available carbon substrate and (2) bioenergetically closest to adult heart tissue cells when cultured in galactose or galactose supplemented with fatty acids. We utilized this model to test a variety of kinase inhibitors with known clinical cardiac liabilities for their potential toxicity toward these cells. We found that the kinase inhibitors showed a dose-dependent toxicity to iPSC cardiomyocytes grown in galactose and that oxygen consumption rates were significantly more affected than adenosine triphosphate production. Sorafenib was found to have the most effect, followed by sunitinib, dasatinib, imatinib, lapatinib, and nioltinib.

Human pluripotent stem cell-derived cardiomyocyte based models for cardiotoxicity and drug discovery

“…Consequently, researchers have begun developing more relevant human model systems for high-throughput in vitro cardiotoxicity testing. As a monolayer or small multicellular aggregates, human pluripotent stem cell-derived CMs (hPSC-CMs) have been used in a wide range of analytical assays to assess the effect of drugs on various cardiobiological parameters: electrophysiology [4], calcium transients [5], contractility [6], cell movement (beating) [7], metabolic activity [8], morphology, and viability [9], alone or in combination [5,[7][8][9].…”

Stem Cells and Stem Cell-derived Tissues and Their Use in Safety Assessment

“…Again, the mechanistic evaluation of cardiotoxicity in a beating model was crucial, as sunitinib was discovered to inhibit hERG as well as other cardiac ion channels in addition to potent cytotoxicity (37). hPSC-derived models of cardiac injury have shown that cardiac troponins and cardiac natriuretic peptides can be useful biomarkers of cardiac damage induced by chemotherapeutic agents (38), as can the release of troponin T and FABP3 (fatty acid-binding protein 3) following doxorubicin-induced cardiac necrosis (39) Using a variety of molecular markers, including mitochondrial membrane potential, endoplasmic reticulum integrity, Ca 2ϩ mobilization, and membrane permeability, combined with an assessment of cell viability, hPSC-derived cardiomyocytes were shown to be more predictive than primary dog cardiomyocytes and H9c2 cells when taking therapeutic concentration into consideration (40,41). Across a panel of cardiotoxic and non-cardiotoxic kinase inhibitors, mitochondrial dysfunction was identified as a critical component of injury of many of these compounds (40).…”

Microfluidic system for enhanced cardiac tissue formation

“…Although these cells are capable of spontaneous beating and show many physiological features of CMs, they remain immature. There are many features in which differences could be observed, including smaller cell size, different shape, different expression levels of ion channels as well as lower oxygen consumption levels and force development [5][6][7][8]. This immature physiology of iPSCderived CMs (iPSC-CMs) leads to differences in pharmacological response to many drugs tested thus far (including tetrodoxin, nisoldipine or lidocaine) [9].…”