Abstract 11290: Mechanical Loading Enhances the Ability to Predict Hypertrophic Cardiomyopathy Phenotypes with Human Induced Pluripotent Stem Cell Derived Cardiac Micro-Tissues

Introduction: Modeling hypertrophic cardiomyopathy (HCM) with human induced pluripotent stem cell (hiPSC) derived cardiomyocytes is challenging because of the immaturity of hiPSC-derived cardiomyocytes along with the need to recapitulate non-genetic factors that contribute to HCM pathogenesis. We assessed the effects of mechanical loading on the action potential waveform morphology of hiPSC-derived micro-heart muscle. We benchmarked these results against action potential morphology measured in primary human cardiomyocytes from HCM patients. Hypothesis: Mechanical loading is necessary for expression of HCM phenotypes in genotype-positive hiPSC cardiomyocyte engineerd tissues Methods: Control and MYBPC3 +/- iPSC were differentiated into cardiomyocytes which were used to form micro-heart muscle atop soft silicone rubber substrates with rigidity matching healthy (15 kPa) or fibrotic heart (65 kPa) muscle. Micro-tissues were stained with voltage sensitive dye to assess action potential duration (APD) under field pacing. Contractility was measured by monitoring the motion of fluorescent beads embedded into the substrates. Freshly isolated surgical specimens from HCM patients were enzymatically digested into single ventricular myocytes and compared to discarded WT donor hearts as controls. Adult cardiomyocytes were stained with the same voltage sensitive dye to measure APD. Results: MYBPC3 +/- micro-tissues had similar action potential waveforms to controls when the tissues worked against a 15 kPa substrate, although the MYBPC3 +/- tissues had higher contractility. On 65 kPa substrates, the degree of hypercontractility in MYBPC3 +/- tissues was less substantial. However, the action potential duration (APD) of these tissues was significantly longer than controls. This increase in APD of hiPSC-cardiomyocytes with an HCM-causing mutation was consistent with an increase in APD observed in primary HCM cardiomyocytes as compared to controls. Conclusions: Mechanical loading may be required to induce electrophysiological aspects of HCM phenotypes in genotype-positive cells to facilitate modeling this disease with iPSC-derived heart tissues.