361 General Discussion - hiPSC-CMs Disease Modelling and Future Perspectives 13 Study type hiPSC lines (number) hiPSC-CMs maturation status Analysis Assesment Outcome ref. Disease modelling MYH7 (5) Proband (5 ) 20-60 days Optical Ca2+ imaging, MEA, patch clamp, confocal microscopy, single-cell qPCR Elucidate mechanisms underlying HCM and test pharmacological restoration MYH7 hiPSCCMs recapitulate HCM phenotype. Screening of 13 drugs revealed Ca2+/Na2+ blocking drugs most efficient to restore beating frequency. Verapamil prevented hypertrophy. 69 Disease modelling Healthy subjects (6) 30 days Overall distribution of action potential Variability of arrhythmias per cell line, per differentiation protocol and batch Even the same cell line and differentiation protocol reveals variability, indicating importance in modeling arrhythmias in hiPSC-CMs. 70 Kinetic image cytometry (KIC) can analyze any individual cells within a full field of view, thereby increasing the identification of heterogeneous proarrhythmic events in each CM, such as early afterdepolarizations. Here, a study by McKeithan et al. proved that hiPSC-CMs from patients with LQTS type 3, facilitated the rapid medicinal chemical refinement of analogs of the drug mexiletine to improve the therapeutic potential and reduce the undesired proarrhythmic activity of this drug.71 Thus, the optical modalities with Ca2+ sensors for recording intracellular Ca2+ concentration used in this study hold a great opportunity for high-throughput (HT) physiological recording. The 3D HT model we described in Chapter 12 has proven to be sufficient for the translation of in vivo clinical data to in vitro to elucidate the full molecular mechanism of the PLN-R14del mutation. Additionally, to the best of our knowledge, we showed for the first time, the kinetic analysis of cardiac pathophysiology by the functional assessment of Ca2+ in an HT 3D spheroid model. Our data compare similarly to alternative cardiac spheroids studies, which used imaging and cellular viability endpoints.72–74 We observed, similarly to the study from McKeithan, that our 3D cardiac spheroids recapitulated decreased Ca2+ handling, as predicted to be disturbed in the PLN-R14del mutation (Chapter 7). As we initiated in Chapter 12, the implementation of more complex 3D in vitro models in HT platforms would be the most suitable for screening disease manifestations with cellautonomous mechanisms, such as cardiomyopathies with morphological, electrophysiological,
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