Switch From Fetal to Adult SCN5A Isoform in Human Induced Pluripotent Stem Cell–Derived Cardiomyocytes Unmasks the Cellular Phenotype of a Conduction Disease–Causing Mutation

Abstract

BackgroundHuman induced pluripotent stem cell–derived cardiomyocytes (hiPSC‐CMs) can recapitulate features of ion channel mutations causing inherited rhythm disease. However, the lack of maturity of these cells is considered a significant limitation of the model. Prolonged culture of hiPSC‐CMs promotes maturation of these cells. We studied the electrophysiological effects of the I230T mutation in the sodium channel gene SCN5A in hiPSC‐CMs generated from a homozygous (I230Thomo) and a heterozygous (I230Thet) individual from a family with recessive cardiac conduction disease. Since the I230T mutation occurs in the developmentally regulated “adult” isoform of SCN5A, we investigated the relationship between the expression fraction of the adult SCN5A isoform and the electrophysiological phenotype at different time points in culture.Methods and ResultsAfter a culture period of 20 days, sodium current (IN a) was mildly reduced in I230Thomo hiPSC‐CMs compared with control hiPSC‐CMs, while I230Thet hiPSC‐CMs displayed no reduction in IN a. This coincided with a relatively high expression fraction of the “fetal” SCN5A isoform compared with the adult isoform as measured by quantitative polymerase chain reaction. Following prolonged culture to 66 days, the fraction of adult SCN5A isoform increased; this was paralleled by a marked decrease in IN a in I230Thomo hiPSC‐CMs, in line with the severe clinical phenotype in homozygous patients. At this time in culture, I230Thet hiPSC‐CMs displayed an intermediate loss of IN a, compatible with a gene dosage effect.ConclusionsProlonged culture of hiPSC‐CMs leads to an increased expression fraction of the adult sodium channel isoform. This new aspect of electrophysiological immaturity should be taken into account in studies that focus on the effects of SCN5A mutations in hiPSC‐CMs.

Patch-Clamp Recording from Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Improving Action Potential Characteristics through Dynamic Clamp

“…Again, recording conditions may play a role [ 4 ], but additional factors such as the employed hiPSC-CMs line, differentiation and dissociation protocols, and the time interval between differentiation and AP recording may also contribute substantially to the apparent differences. Nevertheless, the APD values obtained in the present study are close to the values that we previously observed in our laboratory for control hESC-CMs and hiPSC-CMs [ 5 , 21 , 22 , 26 , 27 , 36 , 37 , 38 , 39 , 40 ]. Preliminary follow-up experiments demonstrate the virtual lack of a carbachol-activated current in our control hiPSC-CMs [ 41 ], which further demonstrates the ventricular nature of these cells, but opposes our speculation regarding the likely presence of “natural” atrial-like hiPSC-CMs in the CTRL group of our present study.…”

A Brief Review of Current Maturation Methods for Human Induced Pluripotent Stem Cells-Derived Cardiomyocytes

“…In hiPSC-CMs, T-tubules are absent and SR is underdeveloped with low expression of SERCA and other key proteins. As a result, hiPSC-CMs rely on L-type channels for the increase of Ca 2+ and ECC is slow (Pesl et al, 2017;Veerman et al, 2017).…”

Human Induced Pluripotent Stem Cells Derived from a Cardiac Somatic Source: Insights for an In-Vitro Cardiomyocyte Platform

“…Furthermore, their current density was found to increase from day 30 to 80 of the differentiation process. Consequently, temporal changes of these properties determine different ionic contribution to the cardiac AP (I Na , I CaL , I K1 ), leading to heterogeneous AP profiles and parameters (diastolic membrane potential, E diast ; AP amplitude, APA; AP duration, APD) [91][92][93].…”