Abstract
Induced pluripotent stem cells (iPSC) offer a unique opportunity for developmental studies, disease modeling and regenerative medicine approaches in humans. The aim of our study was to create an in vitro ‘patient-specific cell-based system' that could facilitate the screening of new therapeutic molecules for the treatment of catecholaminergic polymorphic ventricular tachycardia (CPVT), an inherited form of fatal arrhythmia. Here, we report the development of a cardiac model of CPVT through the generation of iPSC from a CPVT patient carrying a heterozygous mutation in the cardiac ryanodine receptor gene (RyR2) and their subsequent differentiation into cardiomyocytes (CMs). Whole-cell patch-clamp and intracellular electrical recordings of spontaneously beating cells revealed the presence of delayed afterdepolarizations (DADs) in CPVT-CMs, both in resting conditions and after β-adrenergic stimulation, resembling the cardiac phenotype of the patients. Furthermore, treatment with KN-93 (2-[N-(2-hydroxyethyl)]-N-(4methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine), an antiarrhythmic drug that inhibits Ca2+/calmodulin-dependent serine–threonine protein kinase II (CaMKII), drastically reduced the presence of DADs in CVPT-CMs, rescuing the arrhythmic phenotype induced by catecholaminergic stress. In addition, intracellular calcium transient measurements on 3D beating clusters by fast resolution optical mapping showed that CPVT clusters developed multiple calcium transients, whereas in the wild-type clusters, only single initiations were detected. Such instability is aggravated in the presence of isoproterenol and is attenuated by KN-93. As seen in our RyR2 knock-in CPVT mice, the antiarrhythmic effect of KN-93 is confirmed in these human iPSC-derived cardiac cells, supporting the role of this in vitro system for drug screening and optimization of clinical treatment strategies.
Highlights
We focused on catecholaminergic polymorphic ventricular tachycardia (CPVT), a highly lethal inherited arrhythmogenic disease that may cause syncope and sudden death early in life owing to adrenergically mediated bidirectional ventricular tachycardia
Among the putative players in determining the CPVT phenotype, Ca2 þ /calmodulin-dependent serine–threonine protein kinase II (CaMKII) has been recently implicated in arrhythmic events elicited by b-adrenergic activation, and we recently demonstrated that its inhibition is able to prevent ventricular arrhythmogenesis in a mouse model of CPVT.[20,21,22]
Much has been learnt about the pathogenesis of this disease: experimental findings from lipid bilayers as well as knock-in and knockout mouse models suggested that the mechanism underlying the onset of arrhythmia in CPVT patients strictly relies on defective Ca2 þ mobilization within the CM during excitation–contraction coupling
Summary
The usefulness of reprogrammed cells in modelling diseases in vitro has recently been tested for several human congenital cardiovascular diseases: iPSCs have been used for the investigation of monogenic disorders (i.e. long QT (prolongation of Q–T interval combined with torsades de pointes and manifests as several different forms) syndromes, Brugada syndrome/cardiac conduction disease, catecholaminergic polymorphic ventricular tachycardia and other forms of congenital arrhythmias) and disorders in which cardiac defects are part of a multiorgan phenotype (i.e. Leopard and Timothy syndromes).
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