Sex-Related Differences in Drug-Induced QT Prolongation and Torsades de Pointes: A New Model System with Human iPSC-CMs

Numerous drugs have the potential to prolong the QT interval and may cause accidental cardiac arrest (torsades de pointes [TdP]). Women are at a higher risk than men for experiencing drug-induced TdP. Due to the lack of appropriate tools, few studies have investigated whether genetic differences between men and women have any effects on drug-induced proarrhythmia. Sex hormones are believed to play a predominant role in the induction of TdP. Recently, progress in induced pluripotent stem cell (iPSC) technologies has made it possible to utilize human iPSC-derived cardiomyocytes (hiPSC-CMs) to investigate the influence of both genetics and sex hormones on cardiac ion channel gene expression and cardiomyocyte function. In this study, we investigated genetic and hormonal effects on sex differences of drug-induced QT prolongation and TdP with hiPSC-CMs from healthy male and female donors. We found that despite batch variations in beating rates and field potential durations (FPD), female-derived hiPSC-CMs showed steeper slopes of FPD to interspike interval ratios and were more sensitive to IKr blocker-induced FPD prolongation. 17β-estradiol increased FPD and 5α-dihydrotestosterone shortened FPD, but the addition of sex hormones had limited effect on the responses of hiPSC-CMs to IKr blockades. The differential expression of KCNE1 gene and reduced repolarization reserve in female-derived hiPSC-CMs compared with male-derived hiPSC-CMs may partially explain why females are more susceptible to proarrhythmias. Human iPSC-CMs can be a useful new model to study mechanisms of sex differences in cardiomyocyte repolarization processes and aid in the prediction of drug-induced proarrhythmias in both men and women.