Engineered heart tissue models from hiPSC-derived cardiomyocytes and cardiac ECM for disease modeling and drug testing applications

Cardiac tissue engineering provides unique opportunities for cardiovascular disease modeling, drug testing, and regenerative medicine applications. To recapitulate human heart tissue, we combined human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) with a chitosan-enhanced extracellular-matrix (ECM) hydrogel, derived from decellularized pig hearts. Ultrastructural characterization of the ECM-derived engineered heart tissues (ECM-EHTs) revealed an anisotropic muscle structure, with embedded cardiomyocytes showing more mature properties than 2D-cultured hiPSC-CMs. Force measurements confirmed typical force-length relationships, sensitivity to extracellular calcium, and adequate ionotropic responses to contractility modulators. By combining genetically-encoded calcium and voltage indicators with laser-confocal microscopy and optical mapping, the electrophysiological and calcium-handling properties of the ECM-EHTs could be studied at the cellular and tissue resolutions. This allowed to detect drug-induced changes in contraction rate (isoproterenol, carbamylcholine), optical signal morphology (E-4031, ATX2, isoproterenol, ouabin and quinidine), cellular arrhythmogenicity (E-4031 and ouabin) and alterations in tissue conduction properties (lidocaine, carbenoxolone and quinidine). Similar assays in ECM-EHTs derived from patient-specific hiPSC-CMs recapitulated the abnormal phenotype of the long QT syndrome and catecholaminergic polymorphic ventricular tachycardia. Finally, programmed electrical stimulation and drug-induced pro-arrhythmia led to the development of reentrant arrhythmias in the ECM-EHTs. In conclusion, a novel ECM-EHT model was established, which can be subjected to high-resolution long-term serial functional phenotyping, with important implications for cardiac disease modeling, drug testing and precision medicine