Human macrophages directly modulate iPSC-derived cardiomyocytes at healthy state and congenital arrhythmia model in vitro

Abstract

The electrophysiological regulation of cardiomyocytes (CMs) by the cardiac macrophages (M Phi s) has been recently described as an unconventional role of M Phi s in the murine heart. Investigating the molecular and physiological modulation of CM by M Phi is critical to understand the novel mechanisms behind cardiac disorders from the systems perspective and to develop new therapeutic approaches. Here, we developed an in vitro direct coculture system to investigate the cellular and functional interaction between human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and monocyte-derived M Phi s both in healthy-state and congenital arrhythmia disease model associated with SCN5A ion channel mutations. Congenital arrhythmia patient-derived (P) and healthy individual-derived control (C) monocytes and derived M Phi s exhibited distinct M1- and M2-like polarization-related gene expression pattern. The iPSC-CMs and M Phi s formed direct membrane contacts in cocultures demonstrated by time-lapse imaging, scanning electron microscopy, and immunolabeling. The intracellular Ca(2+ )transients were observed in iPSC-CMs and M Phi s when in contact with each other. Interestingly, the C-M Phi s in direct contact with C-CMs significantly accelerated the contraction rates, demonstrating the positive chronotropic effect of M Phi s on healthy cardiac cultures. Furthermore, the M Phi s carrying the SCN5A gene mutation significantly enhanced the arrhythmic events in both C-CMs and P-CMs, implying that the sodium channel mutation in the M Phi is important for the CM function. Importantly, when C-M Phi s were coupled to tachycardic P-CMs, the contraction frequency drastically decreased, and rhythmicity enhanced implicating the amelioration of the disease phenotype in vitro. Consequently, our results indicated the functional regulatory role of M Phi s on human iPSC-CM contractility by membrane contacts in a physiologically relevant in vitro coculture model of both steady-state and arrhythmia. Our findings could serve as a valuable source for the development of effective immunoregulatory therapies for cardiac arrhythmia in the future.