Cell Model of Catecholaminergic Polymorphic Ventricular Tachycardia Reveals Early and Delayed Afterdepolarizations

Kirsi Kujala,Olli Silvennoinen,Mari Pekkanen-Mattila,Lauri Toivonen,Kim Larsson,Jere Paavola,Mika Laine,Kimmo Kontula,Katriina Aalto-Setälä,Anna Lahti,Heikki Swan,Annukka M Lahtinen,Matti Viitasalo

doi:10.1371/journal.pone.0044660

Abstract

BackgroundInduced pluripotent stem cells (iPSC) provide means to study the pathophysiology of genetic disorders. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant inherited ion channel disorder predominantly caused by mutations in the cardiac ryanodine receptor (RyR2). In this study the cellular characteristics of CPVT are investigated and whether the electrophysiological features of this mutation can be mimicked using iPSC -derived cardiomyocytes (CM).Methodology/Principal FindingsSpontaneously beating CMs were differentiated from iPSCs derived from a CPVT patient carrying a P2328S mutation in RyR2 and from two healthy controls. Calcium (Ca2+) cycling and electrophysiological properties were studied by Ca2+ imaging and patch-clamp techniques. Monophasic action potential (MAP) recordings and 24h-ECGs of CPVT-P2328S patients were analyzed for the presence of afterdepolarizations. We found defects in Ca2+ cycling and electrophysiology in CPVT CMs, reflecting the cardiac phenotype observed in the patients. Catecholaminergic stress led to abnormal Ca2+ signaling and induced arrhythmias in CPVT CMs. CPVT CMs also displayed reduced sarcoplasmic reticulum (SR) Ca2+ content, indicating leakage of Ca2+ from the SR. Patch-clamp recordings of CPVT CMs revealed both delayed afterdepolarizations (DADs) during spontaneous beating and in response to adrenaline and also early afterdepolarizations (EADs) during spontaneous beating, recapitulating the changes seen in MAP and 24h-ECG recordings of patients carrying the same mutation.Conclusions/SignificanceThis cell model shows aberrant Ca2+ cycling characteristic of CPVT and in addition to DADs it displays EADs. This cell model for CPVT provides a platform to study basic pathology, to screen drugs, and to optimize drug therapy.

Highlights

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe inherited cardiac disorder characterized by stress-induced polymorphic ventricular tachycardia in a structurally normal heart
These mutations are thought to result in increased release, or leak, of Ca2+ from the sarcoplasmic reticulum (SR) potentially leading to diastolic oscillations of intracellular Ca2+, delayed afterdepolarizations (DAD), and polymorphic ventricular tachycardia [1]
Ca2+ cycling abnormalities were more common in CPVT CMs than in control

Summary

Introduction

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe inherited cardiac disorder characterized by stress-induced polymorphic ventricular tachycardia in a structurally normal heart. CPVT is caused by mutations in the cardiac ryanodine receptor (RyR2) or calsequestrin (CASQ2) gene. RyR2 mutations can be detected in about 70% of patients with CPVT. These mutations are thought to result in increased release, or leak, of Ca2+ from the SR potentially leading to diastolic oscillations of intracellular Ca2+, delayed afterdepolarizations (DAD), and polymorphic ventricular tachycardia [1]. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant inherited ion channel disorder predominantly caused by mutations in the cardiac ryanodine receptor (RyR2). In this study the cellular characteristics of CPVT are investigated and whether the electrophysiological features of this mutation can be mimicked using iPSC -derived cardiomyocytes (CM)

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Conclusion