Abstract 247: Expression and Activity of K ATP Channel in Human Cardiomyocytes Derived from Induced Pluripotent Stem Cells of Nondiabetic and Type II Diabetic Patients

Abstract

Pharmacological preconditioning with volatile anesthetics (APC) protects the myocardium against ischemia/reperfusion injury via multiple pathways that include the cardiac sarcolemmal (sarc) KATP channel. However, APC is altered or absent in metabolic diseases such as diabetes. To investigate the underlying mechanisms we evaluated the expression and activity of cardiac sarcKATP channel in cardiomyocytes (CMs) differentiated from induced pluripotent stem cells of non-diabetic (N-iPSCs) and type II diabetic (DM-iPSCs) patients. Differentiation of human iPSCs into CMs was confirmed by positive immunostaining for cardiac-specific markers and expression of green fluorescent protein under transcriptional control of cardiac promoter myosin light chain-2v that was delivered by lentiviral vector. Immunocytochemical analysis of cardiac sarcKATP channel subunits was carried out with Anti-Kir6.2 and Anti-SUR2A antibodies. Images were captured using a laser-scanning confocal microscope. Single KATP channel activity was monitored from excised inside-out patches at membrane potentials +80 mV to -80 mV, in symmetrical 140 mM K+. The channel was closed by 1 µM glibenclamide and 2 mM ATP. Immunocytochemical analysis showed the presence and colocalization of Kir6.2 and SUR2A proteins in CMs derived from both N-iPSCs and DM-iPSCs. Interestingly, sarcolemmal expression of these subunits appeared lower in DM-iPSCs. Electrophysiological recordings demonstrated that at 5 µM ATP internal single sarcKATP channels were open more frequently in N-iPSCs (7 of 16 cultures) than in DM-iPSCs (3 of 16 cultures). When measured at +40 mV, the single channel current amplitude (2.2 pA) and conductance (55 pS) were typical for the cardiac sarcKATP channel in N-iPSCs. By contrast, the DM-iPSC channels flickered between the open and closed state, resulting in higher noise level and decreased current amplitude (1.6 pA). This is the first report of sarcKATP channel expression and activity in CMs differentiated from human N-iPSCs and DM-iPSCs. The study suggests that compromised APC in human diabetic heart may in part result from altered expression of sarcKATP channel subunits and altered channel kinetics.