Characterization of Human Induced Pluripotent Stem Cell (hiPSC)-Derived Epicardial Cells and Their Involvement in Arrhythmogenic Cardiomyopathy

Abstract

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disease, characterized by progressive fibrofatty replacement of the ventricular myocardium and ventricular arrythmias, potentially leading to sudden cardiac death. Most ACM cases are caused by mutations in the genes encoding the components of the desmosome, with almost half of such mutations found in the PKP2 locus. ACM pathogenesis, while extensively investigated, remains poorly understood, particularly regarding the process of fibrofatty replacement of the ventricular myocardium. The cellular source of the adipocytes that form the fatty deposits in ACM has not been fully elucidated yet. The epicardium, an epithelial cell layer surrounding the myocardium with multipotent and proliferative properties, is a strong candidate for the cellular source of adipocytes in the ACM heart. Furthermore, previous studies have shown that the inflammatory cytokine interferon-gamma (IFNγ) acts as an inhibitor of adipogenesis and considering the involvement of inflammation in ACM, this suggests a role that IFNγ signaling may play in ACM pathogenesis, particularly adipogenesis. In this study, human induced pluripotent stem cell derived epicardial cells (hiPSC-EPCs) with two different ACM-causing PKP2 mutations were used to investigate the cellular contribution of the epicardium to the fatty infiltration in ACM. It was hypothesized that epicardial cells contribute to ACM by increased migration into the myocardium and increased lipid accumulation potential and that IFNγ treatment would attenuate the adipogenic behavior of ACM hiPSC-EPCs. By investigating PKP2 localization, lipid accumulation, cell migration, and gene expression of ACM hiPSC-EPCs, it was found that hiPSC-EPCs with PKP2 mutations demonstrated higher cell migration in vitro but did not have a significantly higher lipid accumulation. Nevertheless, IFNγ treatment resulted in a decrease in lipid accumulation in ACM hiPSC-EPCs. Taken together, the findings of this study suggest that investigating the epicardial involvement in ACM may require studying the interactions of epicardial cells with other heart cell types in disease models that can more closely recapitulate the pathophysiology of the disease. Dissecting the molecular and cellular role of the epicardium in ACM pathogenesis would help increase the current understanding of the early events that bring about the disease’s phenotype and thus would help in the development of novel therapeutics that can address the root cause of ACM.