Abstract
Induced pluripotent stem cells (iPSCs) from type 1 long QT (LQT1) patients can differentiate into cardiomyocytes (CMs) including ventricular cells to recapitulate the disease phenotype. Although optical recordings using membrane potential dyes to monitor action potentials (APs) were reported, no study has investigated the disease phenotypes of cardiac channelopathy in association with the cardiac subtype at the single-cell level. We induced iPSC-CMs from three control and three LQT1 patients. Single-cell analysis using a fast-responding dye confirmed that ventricular cells were the dominant subtype (control-iPSC-CMs: 98%, 88%, 91%; LQT1-iPSC-CMs: 95%, 79%, 92%). In addition, LQT1-iPSC-ventricular cells displayed an increased frequency of early afterdepolarizations (pvalue = 0.031). Cardiomyocyte monolayers constituted mostly of ventricular cells derived from LQT1-iPSCs showed prolonged AP duration (APD) (pvalue = 0.000096). High-throughput assays using cardiomyocyte monolayers in 96-well plates demonstrated that IKr inhibitors prolonged APDs in both control- and LQT1-iPSC-CM monolayers. We confirmed that the optical recordings of APs in single cells and monolayers derived from control- and LQT1-iPSC-CMs can be used to assess arrhythmogenicity, supporting the feasibility of membrane potential dye-based high-throughput screening to study ventricular arrhythmias caused by genetic channelopathy or cardiotoxic drugs.
Highlights
Type 1 long QT syndrome (LQT1), a frequent type of congenital LQT syndrome [1], is caused by a reduction of slow delayed rectifier K+ current (IKs) and is associated with a loss-of-function mutation in the KCNQ1 gene [2]
Optical recordings of single cardiomyocytes identified the cardiac subtypes of each cells and confirmed their variable electrophysiological properties (Figures 3(a)– 3(c)), which was consistent with previous reports of a genetically encoded membrane potential sensor [15, 16]
field potential duration (FPD), an electrophysiological parameter highly correlated with AP duration (APD) [30], of ventricular hiPSC-CM monolayers was longer than that of atrial Induced pluripotent stem cells (iPSCs)-CM monolayers [9], suggesting that the high proportion of the ventricular subtype would be appropriate for analyzing the action potentials (APs) of LQT-iPSC-CM monolayers and drug-induced long QT syndrome (diLQTS) models
Summary
Type 1 long QT syndrome (LQT1), a frequent type of congenital LQT syndrome (cLQTS) [1], is caused by a reduction of slow delayed rectifier K+ current (IKs) and is associated with a loss-of-function mutation in the KCNQ1 gene [2]. Its coexpression with wild-type KCNE1, a beta subunit of the IKs channel, causes a pathological reduction of IKs [4], suggesting the importance of building physiological conditions to recapitulate the pathology in vitro. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were shown to remodel ion channels that regulate the electrophysiological activity of the human heart and to successfully recapitulate the LQT1 phenotype [5,6,7,8]. The field potential duration (FPD), which reflects QT on electrocardiograms (ECG), of ventricular hiPSC-CM
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