Development and validation of an isogenic iPSC-CM model to recapitulate sex-differences in cardiac electrophysiology

About This Grant

PROJECT SUMMARY Sex-based differences in ventricular cardiac pharmacology are well known but remain poorly predicted and understood. In clinical populations, women have a prolonged QT interval when compared to their male counterparts. The female sex-specific prolonged QT phenotype is thought to be linked to disproportionately higher rates (2-4X) of life-threatening drug-induced arrhythmias, such as drug-induced long QT and torsade’s de pointes. This sex-dependent response is often credited to higher expression and function of potassium channels in males and higher calcium handling ability in females. However, previous research into each of these causes is conflicting, often confounded by model-to-model variability and genetic heterogeneity. Additionally, differential sex hormone expression, such as estrogen and testosterone, has been tied to these responses, making the roles of chromosomal sex versus the role of sex hormones difficult to isolate in current pre-clinical model systems. Recently, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC- CM) have emerged as a promising model to predict adverse drug effects. However, a major limitation with these models is the genetic heterogeneity required between male and female lines, making novel discoveries difficult to claim. To address this gap, the proposed project uses isogenic hiPSC-CMs derived from a patient with mosaic Klinefelter Syndrome (XXY) to systematically investigate sex-based differences in the myocyte electrophysiological response to antiarrhythmic drugs. Ventricular XX and XY iPSC-CM were validated thorough flow cytometry, imaging and functional data. Using optical fluorescence assays, it was found that this model system recapitulates the significantly prolonged AP phenotype in XX-CM, which aligns with the prolonged QT interval seen in clinical female populations, both at baseline and under drug perturbation when compared to their male counterparts (Aim 1). This project aims to further quantify this relationship utilizing patch clamping, optical assays, in conjunction with hormonal supplementation (Aim 2) to further understand the role of sex as a complex variable in cardiac pharmacology. By establishing this platform, we aim to predict whether novel reagents have a sex dependent likelihood to become proarrhythmic, informing de novo drug development. The long-term goal is that the introduction of this model system in both cardiac and eventually other tissue types will provide fundamental knowledge about sex differences within human systems to enhance patient health, develop new solutions to reduce illness, and increase quality of life.