Table 1.

Human Relevant Myocyte Models for In Vitro Studies

Construct	Composition and Description	Advantages	Disadvantages
Single hiPSC-CMs	May be micropatterned to form rectangles resembling adult myocytes	Amenable to electrophysiological studies using patch-clamp approaches	No intercalated disk or gap junctions No syncytium function Shape does not equal maturation Single-cell isolation from sheets may cause injury
2D layers	Cardiomyocytes grown in plates or wells in culture Thin film/layers or sheet constructs possible	Ease of preparation Amenable to HTS for electrophysiological, Ca flux, syncytial functions, measures of impulse propagation, fibrillation arrhythmias Cells can be matured by media, patterning extracellular matrix manipulation	Lacks influence of other cardiac cell types and 3D environment of native tissue Variable morphology and sarcomere alignment elicit strain patterns different from native myocytes
2D cocultures	hiPSC-CMs mixed with fibroblasts, vascular cells, mesenchymal stem cells, native adult cardiomyocytes	Mimics heterogeneous cellular composition of native heart Study cell-cell interactions, integrate hiPSC- CMs with noncontractile cells Promotion of hiPSC-CM maturation	Optimum proportions of cell types uncertain Proliferative cells may affect preparation stability and reproducibility Nonmyocyte-to-myocyte coupling may differ from normal tissues
3D organoids	hiPSCs cocultured with fibroblasts/endothelial cells with self-assembly	Mimic 3D cardiac environment Heterogeneous cell types may resemble native heart composition	Spatial arrangements of elements uncertain Difficult to assess electrophysiology and contractility effects with multielectrode arrays and force measures
Engineered human tissues	hiPSC-CMs with/without fibroblasts, endothelial cells	Ability to directly measure contractile force, transmembrane potentials Pacing controls rate More natural alignment of cells/sarcomeres Enhanced myocyte maturation	Initial high myocyte requirements and costs being reduced by miniaturization Lack of vasculature for thicker preparations may create diffusion barrier, anoxic core Low to moderate throughput
3D macroscopic constructs	Ventricular pouches Potential mini-ventricles	Direct pressure measurements possible May promote myocyte maturation	Technically demanding, high cell quantities needed Limited to a few laboratories; low throughput; cost prohibitive

A summary of different hiPSC-CM–derived models used to evaluate various cardiotoxicities. Models have been arranged in order of increasing complexity. In general, the protocols and composition of more complex structures increase the level of phenotypic maturity while challenging reproducibility and assay throughput.

2D indicates 2-dimensional; 3D, 3-dimensional; hiPSC, human induced pluripotent stem cell; hiPSC-CM, human induced pluripotent stem cell–derived cardiomyocyte; and HTS, high-throughput screening.