Heterogeneity and optimal study design between cell lines in induced pluripotent stem cell-based cardiac disease modeling

Human-induced pluripotent stem cell (hiPSC) technologies have provided access to in vitro models of inaccessible human cardiomyocytes (CMs), providing new insights into human disease mechanisms, therapy strategies, and cardiac toxicology. However, the robustness of reproducible outcomes and integration of data among research groups are hampered due to the variation between cell lines, clones, and batches-to-batch differences. These variable outcomes in hiPSC models are caused by differences in human donors, genetic stability, and experimental variability, which affect morphology, cellular heterogeneity, transcript and protein abundance, and differentiation potency. This review summarizes the usage of hiPSC-CMs obtained from multiple lines and evaluates the corresponding experimental variation between studies to perform in-depth in vitro power calculations. Our meta-analyses show that although 4 or more hiPSC lines are used in 21 published case-control studies, these reports still contain high heterogeneity between functional parameters. In specific CM readouts, the SD is >40%, meaning that the variation between different cell lines is larger than the effect of the studied mutation, drug response, or toxicity. Results indicate a need for careful selection of hiPSC lines, controls, and readout stability and these insights will further guide the power of hiPSC lines in biomedical applications.