Improving electrical properties of iPSC-cardiomyocytes by enhancing Cx43 expression

The therapeutic potential of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is limited by immature functional features including low impulse propagation and reduced cell excitability. Key players regulating electrical activity are voltage-gated Na⁺ channels (Na_v1.5) and gap junctions built from connexin-43 (Cx43). Here we tested the hypothesis that enhanced Cx43 expression increases intercellular coupling and influences excitability by modulating Na_v1.5. Using transgenic approaches, Cx43 and Na_v1.5 localization and cell coupling were studied by confocal imaging. Na_v1.5 currents and action potentials (APs) were measured using the patch-clamp technique. Enhanced sarcolemmal Cx43 expression significantly improved intercellular coupling and accelerated dye transfer kinetics. Furthermore, Cx43 modulated Na_v1.5 function leading to significantly higher current and enhanced AP upstroke velocities, thereby improving electrical activity as measured by microelectrode arrays. These findings suggest a mechanistic link between cell coupling and excitability controlled by Cx43 expression in iPSC-CMs. Therefore, we propose Cx43 as novel molecular target for improving electrical properties of iPSC-CMs to match the functional properties of native myocytes.