The Disease-Specific Phenotype in Cardiomyocytes Derived from Induced Pluripotent Stem Cells of Two Long QT Syndrome Type 3 Patients

Azra Fatima,Shao Kaifeng,Matthias Linke,Guoxing Xu,Martin Farr,Filomain Nguemo,Tomo Šarić,Hendrik Milting,Sven Dittmann,Jürgen Hescheler,Ulrich Zechner,Manoj K Gupta,Katriina Aalto-Setala

doi:10.1371/journal.pone.0083005

Abstract

Long QT syndromes (LQTS) are heritable diseases characterized by prolongation of the QT interval on an electrocardiogram, which often leads to syncope and sudden cardiac death. Here we report the generation of induced pluripotent stems (iPS) cells from two patients with LQTS type 3 carrying a different point mutation in a sodium channel Nav1.5 (p.V240M and p.R535Q) and functional characterization of cardiomyocytes (CM) derived from them. The iPS cells exhibited all characteristic properties of pluripotent stem cells, maintained the disease-specific mutation and readily differentiated to CM. The duration of action potentials at 50% and 90% repolarization was longer in LQTS-3 CM as compared to control CM but this difference did not reach statistical significance due to high variations among cells. Sodium current recordings demonstrated longer time to peak and longer time to 90% of inactivation of the Na+ channel in the LQTS-3 CM. This hints at a defective Na+ channel caused by deficiency in open-state inactivation of the Na+ channel that is characteristic of LQTS-3. These analyses suggest that the effect of channel mutation in the diseased CM is demonstrated in vitro and that the iPS cell-derived CM can serve as a model system for studying the pathophysiology of LQTS-3, toxicity testing and design of novel therapeutics. However, further improvements in the model are still required to reduce cell-to-cell and cell line-to-cell line variability.

Highlights

The long QT syndrome (LQTS) is a rare inborn heart condition in which delayed repolarization of the heart following a heartbeat increases the risk of episodes of torsade de pointes [1]
These analyses revealed that this polymorphism was present as a heterozygous allele in all samples (Figure S3 in File S1), suggesting that if any modulation of Nav1.5 function would occur through this polymorphism the effect would be manifested in CM derived from both control and LQTS-3 induced pluripotent stems (iPS) cells and is not expected to be a confounding factor in our experiments
Because of insufficient data for ventricular-like CM from V240M-LQTS-3 iPS cells, statistical analysis of the action potential (AP) parameters was possible only from R535Q-LQTS-3 iPS CM derived from patient NP0012. These analysis showed that the AP parameters, such as the overshoot, maximum diastolic potential (MDP), AP height, AP duration, AP frequency, upstroke rate (Vmax) and AP duration at 50% and 90% repolarization (APD50 and APD90), did not significantly differ between ventricular-like CM derived from R535Q-LQTS-3 iPS cells and control embryonic stem (ES) cell- and iPS cell-derived CM (Table 2)

Summary

Introduction

The long QT syndrome (LQTS) is a rare inborn heart condition in which delayed repolarization of the heart following a heartbeat increases the risk of episodes of torsade de pointes [1]. These episodes may lead to palpitations, fainting and sudden death due to ventricular fibrillation. A large number of mutations in all domains of Nav1.5 have been characterized as leading to or predisposing to LQTS-3 [3] Most of these mutations produce increased persistent sodium current (INa) during the plateau and repolarization phase of the action potential (AP) due to defective open-state inactivation of the

Methods

Results

Conclusion