Electrophysiological and Functional Comparison of Atrial and Ventricular Engineered Heart Tissue Models Using Human Stem Cells Derived Cardiomyocytes - The 65th Annual Conference of the Israel Heart Society & The Israel Society of Cardiothoracic Surgery, 24-25 April 2018

Idit Goldfracht Rappaport Faculty of Medicine and Research Institute, Technion, Haifa, Israel Stephanie Protze McEwen Centre for Regenerative Medicine, UHN, Toronto, Ontario, Canada Assad Shiti Rappaport Faculty of Medicine and Research Institute, Technion, Haifa, Israel Amit Gruber Rappaport Faculty of Medicine and Research Institute, Technion, Haifa, Israel Yulia Nartiss McEwen Centre for Regenerative Medicine, UHN, Toronto, Ontario, Canada Gordon Keller McEwen Centre for Regenerative Medicine, UHN, Toronto, Ontario, Canada Lior Gepstein Rappaport Faculty of Medicine and Research Institute, Technion, Haifa, Israel

Background and Aims: Traditional human pluripotent stem cells (hPSC) differentiation systems result in a mixture of atrial, ventricular, and nodal cells. Here, we aim to advance the field of cardiac tissue engineering by using chamber-specific hPSC-derived cardiomyocytes (CMs) and to compare the electrophysiological and contractile properties of the resulting atrial and ventricular tissues.

Methods and Results: We used developmental biology guided differentiation strategies to direct the differentiation of hPSCs into ventricular or atrial CMs. The specific CMs subtypes were combined with collagen to create engineered heart tissues (EHTs). Immunostainings analysis of the ventricular and atrial EHTs revealed the expression of characteristic ventricular (MLC-2V) or atrial (sarcolipin) markers respectively. The electrophysiological properties were examined by the use of voltage sensitive fluorescent dyes (FluoVolt or Di-4-ANBDQBS). Shorter action potentials duration (APD) were observed in atrial compared to ventricular EHTs (APD90: 230±5 ms vs. 420±10 ms, p<0.0001). Application of the atrial-selective antiarrhythmic agent (Vernakalant) resulted in significant prolongation of the APD in atrial EHTs (by 93%, p<0.0001) but not in ventricular EHTs (by 10%, NS). Conduction velocity was significantly faster in the ventricular (21.4±4.4 cm/s) than in the atrial (4.1±0.2 cm/s) EHTs. Multiple arrhythmogenic reentry circuits were detected in the atrial EHTs either spontaneously or following a mild stimulation protocol, indicating the potential for establishing a 3D model of atrial fibrillation. Finally, detailed contractile analysis revealed a typical length–tension relationship. Interestingly, the ventricular EHTs developed significantly higher active force values than the atrial EHTs (0.92±0.09 vs. 0.19±0.04 mN/mm², p<0.0001).

Conclusions: By using chamber-specific hPSC-derived CMs, we established a clinically-relevant engineered cardiac model for atrial and ventricular tissues. This novel model may bring unique value to the study of developmental biology, disease modeling, drug development, drug testing and regenerative medicine.