Table 2.
Approaches for Assessing In Vitro Cardiotoxicity With hiPSC-CMs
| Biomarker Category | Technological Approaches | Advantages | Disadvantages |
|---|---|---|---|
| Electrophysiology | Transmembrane recordings: action potentials (intracellular electrodes or VSDs) Extracellular recordings: field potential measures (eg, multielectrode arrays); also conduction/propagation |
Ability to assess drug effects on repolarization, depolarization, conduction, propagation; ion current measures with voltage clamp MEA recordings enable longer-term studies of long-term effects and recovery (days to weeks) VSD enables visualization of drug effects on action potential shape, providing insight into currents affected by drugs Reflects biological integration of net effects on multiple ionic currents, exchangers, and pumps not fully reflected in in silico reconstructions |
Variability of myocyte maturation may affect expression; key ion currents (Kir2.1, Nav1.5, Ip etc) differ from native adult myocyte Repolarization waveform from MEA recordings may be difficult to measure and interpret Effects on repolarization using simpler surrogate measures (contractility, cell movement) may be challenging Single-cell recordings possible but technically difficult and prone to potential artifacts from cell isolation |
| Contractility | Impedance measures linked to overall motion of myocytes sheets Ca2+ transient to assess EC coupling Edge displacement and traction force to assess contraction and relaxation Direct force measurements possible with thin film and myotube constructs |
Measures represent surrogates of pump function with different translational fidelity | Disorganized sarcomeric structure, lack of t tubules in some constructs contribute to reduced force; calcium handling may be immature Lack of anisotropic morphology may distort contractility assessments Calcium-handling dysregulation linked to negative force-frequency relationship |
| Injury/structural damage | Measures of secreted/released proteins (troponins, proBNP), microRNAs, exosomes Mitochondrial markers (mitochondrial membrane potential, morphology, number) Morphology (cellular/organelle characteristics, cell viability markers) Monitoring apoptosis/cytotoxicity with fluorescent dyes/time-lapse imaging |
HTS is possible, full-dose responses, days to weeks of exposure possible; reversibility studies possible Application of any substance to human heart tissue in vitro without risk to patients Assessing early apoptosis induced by chemotherapy |
Lack of neuronal and humoral influences present in intact myocardium Difficult to replicate time course of in vivo exposures (parent and metabolite) in longer-term in vitro studies Known resistance to hypoxic injury in some preparations Immunological responses to removing products of cellular injury or dead cells are absent |
A summary of different approaches for assessing cardiotoxicity on the basis of toxicity type (electrophysiology, contractility, and injury/structural damage).
EC indicates excitation-contraction; hiPSC-CM, human induced pluripotent stem cell–derived cardiomyocyte; HTS, high-throughput screening; MEA, microelectrode array; proBNP, pro-B-type natriuretic peptide; and VSD, voltage-sensitive dye.