Induced pluripotent cardiomyocytes from female CPVT patient present different Ca2+ mishandling than men

Abstract

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited disease manifested as syncope or sudden death in children and young adults. The ryanodine receptor (RyR2) R420Q mutation was identified in a 14-year-old boy who died suddenly. We generated human induced pluripotent (h-iPS) derived cardiomyocytes from two sisters. As most of sudden death occurs in males, we had the hypothesis that there might be some sex-dependent differences. We aim to elucidate the key role of [Ca 2+ ] i in the genesis of cardiac arrhythmia in female RyR2 R420Q CPVT patients. We generated hiPSC-CM from two sisters, one carrier and the other non-carrier. We assessed intracellular [Ca 2+ ] i handling both spontaneous and during electrical pacing at 1 Hz by confocal microscopy. For SR Ca 2+ load quantification, h-iPS-CMs were rapidly perfused with 10 mmol/L caffeine. To induce β-adrenergic activation, 100 nM isoproterenol (ISO) was added in some experiments. All confocal Ca 2+ images were analysed by homemade routines using IDL software. First, we found that woman CPVT h-iPS-CMs presented longer cycle length than wt cells, correlating with the bradycardia observed in CPVT patients. The amplitude of the Ca 2+ transients were significantly higher for CPVT h-iPS-CMs compared to wt; however Ca 2+ transients did not change in CPVT h-iPS-CMs, after ISO perfusion. SR Ca 2+ load presented no differences between groups but the time decay constant of the caffeine-evoked Ca 2+ transients were faster in CPVT h-iPS-CMs whereas it became slower after ISO perfusion. Moreover, Ca 2+ pro-arrhythmogenic events were significantly higher in CPVT h-iPS-CMs compared to wt h-iPS-CMs whereas similar values were observed in CPVT cells after ISO perfusion. Although pro-arrythmogenic events were similarly higher in both male and female hiPSC-CM, the Ca 2+ handling characteristics were slightly different. The RyR2R420Q mutation in woman CPVT h-iPS-CMs provides a reliable model to study CPVT in human context.