Epicardial signal modulation in cardiac diseases
Final Report Abstract
Studies have shown that the interaction between the epicardial adipose tissue, the embedded coronaries and the myocardium plays a key role during the development of coronary artery disease (CAD). Here we aimed to break down the cellular composition of the epicardium and to contextualize their endocrine, metabolic and inflammatory function. Therefore, single nuclei RNA sequencing (SN-RNAseq) built the base to detect differences between patients with/ without CAD undergoing cardiac surgery. We also aimed to see whether or not there are differences in patients with reduced (rEF) and preserved (pEF) left ventricular ejection fraction. For the first time, the cellular composition of the epicardial adipose tissue was decoded; it consisted mainly of adipocytes (ADPC), hematopoetic cells (macrophages, MP, T-and B-cells), stromal cells (EpiSC), endothelial cells, smooth muscle cells and epithelial epicardial cells (EPC). CAD patients’ samples showed significantly more EpiSC in comparison. On the other hand, more ADPC were detected in non-CAD patients (n.s.). Regarding cellular composition, no difference was found in patients with a rEF or pEF. Gene-set-enrichement analysis revealed that inflammation (TNFα pathway) and epithelial to mesenchymal transitioning (EMT) were upregulated in epicardial cells of CAD patients (mainly in EPC). SN-RNAseq data was validated using in vitro assays (qRT-PCR, ELISA). EMT and derivative mechanisms such as fibrosis and angiogenesis were analyzed. Cells of both patient populations had the capacity to undergo EMT (n.s. difference). Conditioned media of all cell types was collected and used for several functional assays to determine their individual function in disease development. CAD-ADPC CM inhibited angiogenesis more than non-CAD- ADPC CM. In contrast, non-CAD-MP CM stimulated angiogenesis in comparison to CAD-MP CM. EpiSC of both groups stimulated angiogenesis. All epicardial cells in both groups had antifibrotic properties. Furthermore, CAD-EpiSC tended to differentiate better into ADPC than non-CAD-EpiSC. The results of our studies revealed an impact of inflammation for the development of CAD on a cellular level. Furthermore, we showed that EMT also plays a role in human epicardium. Interestingly, epicardial cells of both patient groups showed anti-fibrotic properties. However, ADPC of CAD patients inhibited angiogenesis. Our results indicated that CAD-EpiSC were more susceptible to differentiate into ADPC, potentially revealing the importance of the interaction between EpiSC, ADPC and coronaries. Further analysis is necessary to develop a better understanding of the underlying mechanisms.
