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HCN2 and TBX3 Reprogram Human-Induced Pluripotent Stem Cells-Derived Cardiomyocytes into Pacemaker-Like Cells.

TBX3 reprograms cardiac myocytes into cells that possess sinoatrial node phenotype, but no specific funny current (If) was detected. We explore whether overexpression of TBX3 alone or combined with HCN2 can reprogram human-induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) into pacemaker-like cells. HiPSC-CMs were transfected with TBX3 and/or HCN2 in this study. Expression analysis showed that overexpression of TBX3 induces a reduced reduction expression profile of working cardiomyocytes into that of pacemaker cells. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and electrophysiological analyses showed a reduced expression of connexins subunits (CX40, CX43), the sodium current (SCN5A, INa), the inward rectified potassium channels (Kir2.1, IK1), and an increased expression of connexins subunits (CX30.2, CX45). No If was detected. The reduction of IK1 resulted in a more depolarized maximum diastolic potential together with an expression of If (generated by HCN2), which they work in synergy to generate spontaneous diastolic depolarization that was the most typical characteristic of pacemaker cells. In conclusion, overexpression of TBX3 and HCN2 could reprogram hiPSC-CMs into pacemaker-like cells. The ability to enable diastolic depolarization formation provides a new strategy for the construction of a biological pacemaker.