Functional abnormalities in iPSC‐derived cardiomyocytes generated from CPVT1 and CPVT2 patients carrying ryanodine or calsequestrin mutations

Abstract

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia characterized by syncope and sudden death occurring during exercise or acute emotion. CPVT is caused by abnormal intracellular Ca2+ handling resulting from mutations in the RyR2 or CASQ2 genes. Because CASQ2 and RyR2 are involved in different aspects of the excitation-contraction coupling process, we hypothesized that these mutations are associated with different functional and intracellular Ca²+ abnormalities. To test the hypothesis we generated induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CM) from CPVT1 and CPVT2 patients carrying the RyR2R420Q and CASQ2D307H mutations, respectively, and investigated in CPVT1 and CPVT2 iPSC-CM (compared to control): (i) The ultrastructural features; (ii) the effects of isoproterenol, caffeine and ryanodine on the [Ca2+]i transient characteristics. Our major findings were: (i) Ultrastructurally, CASQ2 and RyR2 mutated cardiomyocytes were less developed than control cardiomyocytes. (ii) While in control iPSC-CM isoproterenol caused positive inotropic and lusitropic effects, in the mutated cardiomyocytes isoproterenol was either ineffective, caused arrhythmias, or markedly increased diastolic [Ca2+]i. Importantly, positive inotropic and lusitropic effects were not induced in mutated cardiomyocytes. (iii) The effects of caffeine and ryanodine in mutated cardiomyocytes differed from control cardiomyocytes. Our results show that iPSC-CM are useful for investigating the similarities/differences in the pathophysiological consequences of RyR2 versus CASQ2 mutations underlying CPVT1 and CPVT2 syndromes.

Patient-Specific Drug Screening Using a Human Induced Pluripotent Stem Cell Model of Catecholaminergic Polymorphic Ventricular Tachycardia Type 2

“…Subsequently, many hiPSC-CMs models of both CPVT types [20][21][22][23][24][25][26][27][28][29] were shown to recapitulate the clinical phenotype in the culture-dish by displaying abnormal Ca 2+ handling and arrhythmias. Here, we focused on CPVT2 and found, similar to previous reports, 24,25,29 21,30 We recently investigated this phenomenon in a CPVT1-hiPSC-CMs model demonstrating a reduced SOICR threshold in the affected cells. 21 Here, we demonstrated the ability to model SOICR also in the CPVT2-hiPSC-CMs and revealed that the D307H-CASQ2 may also reduce SOICR threshold in the affected cardiomyocytes.…”

“…7,8 In the cardiac field, hiPSCs were established from healthy individuals and from patients inflicted with acquired 9 and several types of inherited cardiac disorders. 10,11 Patient-specific hiPSC-derived cardiomyocyte (hiPSC-CM) models of different inherited arrhythmogenic syndromes (including the long-QT, [12][13][14][15] Brugada, 16 and sodium channel overlap 17 syndromes; arrhythmogenic right ventricular cardiomyopathy 18,19 ; and both types of CPVT [20][21][22][23][24][25][26][27][28][29] ) were…”

Human Induced Pluripotent Stem Cells as a Platform for Personalized and Precision Cardiovascular Medicine

“…This supported the mechanistic explanation that increased diastolic Ca 2ϩ can lead to the development of arrhythmias. In a separate study, ultrastructural characterization demonstrated that hiPSC-CMs from CPVT1 patients also have enlarged mitochondrial, glycogen, and lysosome clusters, as well as thinner Z-bands, reduced number of sarcomeres per cell, and increased sarcomere disarray (206). These phenotypes were more pronounced in CPVT2 hiPSC-CMs, demonstrating that hiPSCs provide a setting for the investigation of the similarities and differences in the pathophysiological consequences of different mutations.…”

Puerarin Enhances Ca2+ Reuptake and Ca2+ Content of Sarcoplasmic Reticulum in Murine Embryonic Stem Cell-Derived Cardiomyocytes via Upregulation of SERCA2a

“…Liu et al have reported a facilitated maturation of Ca 2+ handling properties of transgenic hES-CMs with CSQ overexpression. CSQ is a high-capacity but low affinity Ca 2+ binding protein in the SR, playing an important role in regulating excitation-contraction coupling and CICR in the heart [16, 30-31]. It serves as a major Ca 2+ buffer that modulate RyR activity through Jn and Trd, and also as a reservoir for Ca 2+ readily accessible for CICR [31].…”