4 research outputs found
Deep phenotyping of human induced pluripotent stem cell-derived atrial and ventricular cardiomyocytes.
Generation of homogeneous populations of subtype-specific cardiomyocytes (CMs) derived from human induced pluripotent stem cells (iPSCs) and their comprehensive phenotyping is crucial for a better understanding of the subtype-related disease mechanisms and as tools for the development of chamber-specific drugs. The goals of this study were to apply a simple and efficient method for differentiation of iPSCs into defined functional CM subtypes in feeder-free conditions and to obtain a comprehensive understanding of the molecular, cell biological, and functional properties of atrial and ventricular iPSC-CMs on both the single-cell and engineered heart muscle (EHM) level. By a stage-specific activation of retinoic acid signaling in monolayer-based and well-defined culture, we showed that cardiac progenitors can be directed towards a highly homogeneous population of atrial CMs. By combining the transcriptome and proteome profiling of the iPSC-CM subtypes with functional characterizations via optical action potential and calcium imaging, and with contractile analyses in EHM, we demonstrated that atrial and ventricular iPSC-CMs and -EHM highly correspond to the atrial and ventricular heart muscle, respectively. This study provides a comprehensive understanding of the molecular and functional identities characteristic of atrial and ventricular iPSC-CMs and -EHM and supports their suitability in disease modeling and chamber-specific drug screening
hiPSC-derived cardiomyocytes from Brugada Syndrome patients without identified mutations do not exhibit clear cellular electrophysiological abnormalities
Brugada syndrome (BrS) is a rare cardiac rhythm disorder associated with sudden cardiac death. Mutations in the sodium channel gene SCN5A are found in similar to 20% of cases while mutations in other genes collectively account for <5%. In the remaining patients the genetic defect and the underlying pathogenic mechanism remain obscure. To provide insight into the mechanism of BrS in individuals without identified mutations, we here studied electrophysiological properties of cardiomyocytes (CMs) generated from human induced pluripotent stem cells (hiPSCs) from 3 BrS patients who tested negative for mutations in the known BrS-associated genes. Patch clamp studies revealed no differences in sodium current (I-Na) in hiPSC-CMs from the 3 BrS patients compared to 2 unrelated controls. Moreover, action potential upstroke velocity (V-max), reflecting INa, was not different between hiPSC-CMs from the BrS patients and the controls. hiPSC-CMs harboring the BrS-associated SCN5A-1795insD mutation exhibited a reduction in both I-Na and V-max, demonstrating our ability to detect reduced sodium channel function. hiPSC-CMs from one of the BrS lines demonstrated a mildly reduced action potential duration, however, the transient outward potassium current (I-to) and the L-type calcium current (I-Ca,I-L), both implicated in BrS, were not different compared to the controls. Our findings indicate that ion channel dysfunction, in particular in the cardiac sodium channel, may not be a prerequisite for Br