Chronic Exposure to Testosterone Increases Expression of Transient Outward Current in Human Induced Pluripotent Stem Cell (hiPSC)-Derived Cardiomyocytes (CM)

Abstract

Background The transient outward potassium current (I to ) plays a prominent role in the development of cardiac arrhythmias associated with the J-wave syndromes, including Brugada and early repolarization syndromes. The J-wave syndromes are strongly male-dominated, presumably due to higher expression of I to in the right ventricular epicardium of male vs female dogs. In this study we tested the hypothesis that the male androgen testosterone underlies these gender differences by examining its influence on expression of I to in hiPSC-derived cardiomyocytes. Methods and Results Embryoid bodies (EBs) were made from a human iPS cell line reprogrammed with Oct4, Nanog, Lin28, and Sox2 using a serum-free differentiation protocol supplemented with growth factors for selective cardiac differentiation. The beating clusters were microdissected from the entire EBs, enzymatically dissociated, and plated on fibronectin-coated dishes. Cells were treated with 1 µM testosterone for 4 weeks. I to was measured using whole-cell patch-clamp techniques at 36oC. I to density was significantly greater in testosterone-treated hiPSC CMs compared to controls (18.7 ± 3.2 pA/pF vs 11.8 ± 1.6 pA/pF, 1 μM testosterone, P P = .036). Steady state (SS) inactivation was unchanged. Expression of the I to -associated gene transcript (KCND3, Kv4.3) was 547.51% greater ( P to from inactivation and a depolarized MDP (–65.4 ± 10.3 mV) due to a deficient I K1 . Conclusions Our results suggest that testosterone is capable of increasing expression of I to , at least in part by upregulating expression of Kv4.3 mRNA. These results provide insights into the gender-dependent expression of I to and may explain the marked gender differences observed in the manifestation of life-threatening arrhythmias associated with the J-wave syndromes. [Supported by NYSTEM contract # C026424.]