Long Chains Fatty Acids Induce Differentiation of Epicardial Progenitor Cells into Adipocytes Through Preadipocyte Marker DLK1

The atrial fibrillation (AF), the most frequent cardiac arrhythmia is most often the clinical expression of the atrial cardiomyopathy. The epicardial adipose tissue (EAT) is now considered as an important component of the atrial cardiomyopathy notably when AF is associated metabolic disorders such as obesity. We previously showed that the epicardial progenitor cells (EPC) are the main source of EAT. Here we tested the hypothesis that long chain free fatty acids (LCFFA) present in the serum of patients with metabolic disorders can induce the differentiation of EPC into adipocytes. First, characterization of the effects LCFFA oleate (OLE) and palmitate (PAL) on differentiation of EPC; second, to examine the involvement of DLK1/Pref-1, a key actor of adipogenesis in the differentiation of EPC into adipocytes. In a rat model of atrial cardiomyopathy secondary to ischemic heart failure, EPC were harvested and cultured in presence of OLE (500 μM) and PAL (250 μM) for 7 days. EPC-derived adipocytes were characterized with oil red-O staining and Bodipy labelling. The transcriptomic of EPC was performed with single cell RNA sequencing together with a gene expression of EPC-derived adipocytes performed with qPCR at 3 and 7days after treatment. Soluble form of Pref-1 was measured in supernatant of EPC treated by using ELISA assay. The Notch/Pref-1 signaling pathway was investigated with biochemistry approach. After 3 days, the subpopulation of EPC expressing pref1 accumulated lipid droplets evidenced by red oil. At day 7, DLK1 expression was decreased whereas that of the adipogenic marker PPARγ was increased at the transcriptomic level (n = 5; P < 0.05). Furthermore, the expression of short soluble form of Pref-1 accumulated in supernatant of EPC indicated the shedding of the protein. Preliminary data indicated an effect of the short soluble form of Pref-1 on EPC proliferation. Single cell RNA sequencing revealed Notch expression in cluster of EPC engaged in the adipocyte differentiation pathway. Serum long chain fatty acid can trigger the adipogenic differentiation of EPC and DLK1/Notch signaling pathway appears to be an early step during this process. It remains to determine mechanisms of lipidic receptor GPR40 in EPC differentiation and the contribution to the expansion of atrial EAT during metabolic diseases.