Dantrolene rescues arrhythmogenic RYR2 defect in a patient‐specific stem cell model of catecholaminergic polymorphic ventricular tachycardia

Abstract

Coordinated release of calcium (Ca2+) from the sarcoplasmic reticulum (SR) through cardiac ryanodine receptor (RYR2) channels is essential for cardiomyocyte function. In catecholaminergic polymorphic ventricular tachycardia (CPVT), an inherited disease characterized by stress-induced ventricular arrhythmias in young patients with structurally normal hearts, autosomal dominant mutations in RYR2 or recessive mutations in calsequestrin lead to aberrant diastolic Ca2+ release from the SR causing arrhythmogenic delayed after depolarizations (DADs). Here, we report the generation of induced pluripotent stem cells (iPSCs) from a CPVT patient carrying a novel RYR2 S406L mutation. In patient iPSC-derived cardiomyocytes, catecholaminergic stress led to elevated diastolic Ca2+ concentrations, a reduced SR Ca2+ content and an increased susceptibility to DADs and arrhythmia as compared to control myocytes. This was due to increased frequency and duration of elementary Ca2+ release events (Ca2+ sparks). Dantrolene, a drug effective on malignant hyperthermia, restored normal Ca2+ spark properties and rescued the arrhythmogenic phenotype. This suggests defective inter-domain interactions within the RYR2 channel as the pathomechanism of the S406L mutation. Our work provides a new in vitro model to study the pathogenesis of human cardiac arrhythmias and develop novel therapies for CPVT.

Generation of Human Cardiomyocytes: A Differentiation Protocol from Feeder-free Human Induced Pluripotent Stem Cells

“…Electrophysiological analysis of these cells revealed a heterogeneous population comprising cells with nodal, atrial, and ventricular profiles (data not shown, Priori, S.G., et al, J. Clin. Invest., In Press, 14,15,20 ). …”

Disease Models for the Genetic Cardiac Diseases

“…Notably the model with RyR2-P2328S mutation also exhibited early after depolarizations (EADs) in addition to DADs suggesting suggesting another pathophysiological mechanism for CPVT [85]. Intriguing finding was also the effect of dantrolene in rescuing the arrhythmogenic phenotype [84].…”

“…Multiple iPS-based CPVT disease models have been published, most of them having the disease specific mutation in the RyR2 gene while [83][84][85] and one having the mutation in the CASQ2 gene [86]. The congruent result from these CPVT model studies was the occurrence of delayed after depolarizations (DADs) and arrhythmias which are caused by the aberrant diastolic Ca 2+ from the SR.…”

Cardiac regeneration using HLA-matched induced pluripotent stem cells—no monkey business, but still a long and winding road ahead

“…This requires not only the formation of gap junctions with the adjacent cardiomyocytes, but also an intracellular calcium cycling machinery that is able to generate repetitive calcium waves at physiologic heart rates. This aspect is not trivial, since in vitro differentiated iPSC-derived cardiomyocytes are typically immature with respect to calcium cycling (8), and the achievable beating rates are often lower than the physiological heart rates of the respective species (9). Incomplete coupling or failure to adapt to higher heart rates would not only prevent the grafted cells from improving cardiac function, but may also represent a risk for the development of arrhythmias with potentially fatal outcome.…”