Disease Phenotypes and Mechanisms of iPSC-Derived Cardiomyocytes From Brugada Syndrome Patients With a Loss-of-Function SCN5A Mutation

Abstract

Brugada syndrome (BrS) is one of the major causes of sudden cardiac death in young people, while the underlying mechanisms are not completely understood. Here, we investigated the pathophysiological phenotypes and mechanisms using induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) from two BrS patients (BrS-CMs) carrying a heterozygous SCN5A mutation p.S1812X. Compared to CMs derived from healthy controls (Ctrl-CMs), BrS-CMs displayed a 50% reduction of I Na density, a 69.5% reduction of Na V 1.5 expression, and the impaired localization of Na V 1.5 and connexin 43 (Cx43) at the cell surface. BrS-CMs exhibited reduced action potential (AP) upstroke velocity and conduction slowing. The I to in BrS-CMs was significantly augmented, and the I CaL window current probability was increased. Our data indicate that the electrophysiological mechanisms underlying arrhythmia in BrS-CMs may involve both depolarization and repolarization disorders. Cilostazol and milrinone showed dramatic inhibitions of I to in BrS-CMs and alleviated the arrhythmic activity, suggesting their therapeutic potential for BrS patients.

Blebbistatin protects iPSC-CMs from hypercontraction and facilitates automated patch-clamp based electrophysiological study

“…The peak I Na appeared at -20 mV in Ctrl1-and Ctrl2-CMs showed as -114.9 ± 11.7 and -117.5 ± 20.7 pA/pF, and in BrS1-and BrS2-CMs presented as -63.5 ± 7.3 and -45.9 ± 6.0 pA/pF, respectively. These results generated by using APC were consistent with our previous results acquired with MPC, which also revealed a more than 50% reduction of I Na density in BrS-CMs [34].…”

“…The peak I to at +60 mV in BrS1-CMs (9.7 ± 2 pA/pF) and BrS2-CMs (10.8 ± 2.2 pA/pF) were significantly bigger than those in Ctrl1-CMs (4.7 ± 0.5 pA/pF) and Ctrl2-CMs (5.7 ± 0.8 pA/pF) (Figure 4C and D). The I to recorded with APC are in line with our previous publication of MPC results: the I to at +60 mV in BrS1-CMs and BrS2-CMs were 2.4 and 1.9 times bigger than those in Ctrl-CMs [34]. Furthermore, consistent with our MPC data, we did not observe any I CaL density differences between Ctrl-CMs and BrS-CMs (Figure 4 E, F).…”

“…To study whether human iPSC-CMs under BB-buffered condition can be used with APC for disease modelling, we repeated I Na recording under 50 mM [Na + ] o using APC in previously published BrS disease models [34]. In the presence of 2.5 µM BB, single iPSC-CMs were obtained from two healthy donors (Ctrl1 = iBP76.…”

Recent progress of iPSC technology in cardiac diseases

“…Schwartz et al tested if the in vitro results can be applied clinically to patients with LQTS2 and demonstrated that the combination of lumacaftor and ivacaftor, which is also commonly used to treat cystic fibrosis (Orkambi, Vertex Pharmaceuticals, Inc.), significantly shortened the QT interval, indicating that the drugs discovered from iPSC-based disease modeling can potentially translate clinically (Schwartz et al 2019 ). Similarly, numerous studies have modeled other channelopathies, such as catecholaminergic polymorphic ventricular tachycardia (CPVT) caused by RYR2 or CASQ2 mutations and Brugada syndrome caused by SCN5A mutations (Liang et al 2016 ; Jung et al 2012 ; Sasaki et al 2016 ; Preininger et al 2016 ; Li et al 2020 ). All these studies demonstrated that patient iPSC cardiomyocytes can recapitulate the disease-specific phenotypes, such as abnormal calcium handling and triggered activity, highlighting the effectiveness of iPSC-based disease modeling for channelopathy research.…”

Patient-specific induced pluripotent stem cells as “disease-in-a-dish” models for inherited cardiomyopathies and channelopathies – 15 years of research

“…Importantly, in patient-derived iPSC-CMs, treatment with 4-Aminopyridine, an Ito blocker, completely reversed the increased phase-1 repolarization and restored the APD, indicating a coordinated role of INa and Ito in the arrhythmogenic mechanism of BrS. In-depth analysis of iPSC-CMs derived from two BrS subjects with an SCN5A -S1812X variant revealed reduced INa, amplified Ito, and increased ICaL window current probability along with conduction slowing, demonstrating coexistence of repolarization and depolarization impairment in diseased cells[ 121 ].…”