Abstract P009: Notch Signaling Regulates Pluripotent Gene Expressions in Cardiac c-Kit+ Cells

We and others have shown that transplantation of explant-derived cells (EDCs) obtained from cardiac biopsies improved cardiac function after myocardial infarction. The current study was designed to examine the molecular mechanisms regulating expression of pluripotent genes in these cells. Toward this end, EDCs were separated based on expression of c-Kit antigen after 21 days in culture. We found that Notch signaling was activated mainly in c-Kit+ cells, but to a lesser degree in c-Kit- cells. In addition, we found that the pluripotency markers Sca-1, Nanog and Sox2 were mainly expressed in c-Kit+ cells. Also, in c-Kit+ cells, forced activation of Notch signaling via over-expression of Notch intracellular domain (NICD) induced cellular and molecular changes typical of epithelial-mesenchymal transition (EMT), evident by a decrease in VE cadherin and increases in N-cadherin, MMP, and ICAM. . Suppression of Notch signaling was associated with c-Kit+ cells exhibition of an epithelial/endothelial morphology. This observation is further supported by the increase in Nanog, Sca1, Sox2, VEGFR2 gene expressions after Notch suppression. In contrast, overexpression of NICD resulted in down-regulation of pluripotency gene expressions. Furthermore, suppression of Notch signaling was coincided with stabilization of β-catenin and accumulation of phosphorylated glycogen synthase kinase 3 beta (pGSK3β) suggestive of a crosstalk between Notch and canonical Wnt pathway. Thus, Notch regulates expression of pluripotency genes and mesenchymal transition of c-Kit+ cardiac EDCs.