Characterization Of Sarcolemmal K-Atp Channels In Human Ipsc-Derived Cardiomyocytes

Background: The ATP-sensitive potassium channel (KATP) plays a key role in protecting heart muscle during metabolic challenges such as ischemia. KATP activation causes action potential shortening that reduces calcium entry and contraction thus reducing calcium overload induced damage and preserving energy reserves. Cardiomyocytes derived from human inducible pluripotent stem cell (hiPSC) have emerged as a model to study cardiac function, however there are few studies that have focused on KATP. Methods: In the present study, cardiomyocytes were either generated from hiPSC using heparin- based chemically defined media or purchased from Cellular Dynamics (iCells2). Expression of the pore-forming (Kir6.2) and regulatory (SUR1 & SUR2) subunits of the KATP channel during differentiation were assessed using western blot. KATP function was assessed by measuring the field potential duration (FPD) and spontaneous beat rate in a confluent monolayer using the Axion Maestro multielectrode array system. Cells were probed using the KATP activators P1075 and diazoxide, specific for SUR2 and SUR1, respectively. Results: We found that the pore-forming subunit of the sarcolemmal KATP channel (Kir6.2) was expressed in iPSC and maintained throughout the course of differentiation. Consistent with the typical composition of sarcolemmal KATP, we observe a significant increase of SUR2 but little SUR1 protein following Wnt inhibition. Functionally, the FPD is markedly reduced by P1075 in a concentration-dependent manner, with 24% reduction at 100 nM and 92 % reduction at 100 μM. Moreover, glibenclamide 10μM reduces FPD shortening confirming a role for KATP. Finally, we observe little change in FPD when cells are exposed to diazoxide (100 μM) consistent with reduced SUR1 protein levels. Conclusion: These results indicate that cardiomyocytes derived from human iPSC express the KATP channel composed of primarily the SUR2 isoform and suggest that iPSC derived cardiomyocytes would be an effective model for studying the role of KATP during metabolic challenges.