Ph.D Thesis

Ph.D StudentGoldfracht Idit
SubjectDevelopment of an Engineered Human Heart Tissue Model from
Human iPSCs-Derived Cardiomyocytes
DepartmentDepartment of Biotechnology
Supervisor PROF. Lior Gepstein


The combination of tissue engineering and human induced pluripotent stem cells derived cardiomyocytes (hiPSCs-CMs) technologies provide unique opportunities for cardiovascular disease modeling, drug testing, and regenerative medicine applications. To achieve these goals, we aimed to establish clinically-relevant engineered human heart tissue models through the use of several novel techniques. To recapitulate human heart tissue, we combined 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 corresponding 2D-cultured hiPSC-CMs. Force measurements from the ECM-EHTs 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 also allowed to detect drug-induced changes in contraction rate, optical signal morphology, cellular arrhythmogenicity and alterations in tissue conduction properties. 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.

Next, we aimed to develop functional EHTs comprised of chamber-specific hPSC-CMs. We showed that such EHTs can be generated by directing hPSCs to differentiate into ventricular or atrial cardiomyocytes, and then embedding these cardiomyocytes in a collagen-hydrogel to create chamber-specific, ring-shaped, EHTs. The chamber-specific EHTs displayed distinct atrial versus ventricular phenotypes as revealed by immunostaining, gene-expression, optical assessment of action-potentials and conduction velocity, pharmacological, and mechanical force measurements. We also established an atrial EHT-based arrhythmia model (atrial fibrillation) and confirmed its usefulness by applying relevant pharmacological interventions

In conclusion, novel models of ECM-EHT and chamber-specific EHTs were established. These models could have important implications for cardiac disease modeling, regenerative medicine, drug testing and developmental biology applications.