447. Notch Activation Enchances Vascular Lineage Commitment of Cardiac Stem Cells

Abstract

Notch signaling pathway is an evolutionary conserved system that control heart development and could be important for cardiac tissue renewal and regeneration after injury by controlling the maintenance and commitment of a cardiac stem cell compartment. However the precise cell targets of Notch signaling in the mammalian damaged heart remain poorly defined. OBJECTIVE: To investigate the functional role of Notch signaling in the regulation of cardiac stem cells (CSCs) commitment in ischemic mice myocardium. METHODS AND RESULTS: Notch 1 receptor, their ligands and markers of cardiomyocyte, SMC, and endothelial cell lineages were examined in undamaged and infarcted C57BL/6 mice hearts by immunofluorescence staining. We have found that the majority of c-kit+ CSCs were nested in the interstitium between cardiomyocytes, and expressed Notch 1 receptor. Ligand Jagged 1 is presented on cardiomyocyte and cardiac fibroblasts, localized near c-kit+Notch1+ CSCs. Conversely, Delta-like4 ligand expressed on the endothelial and smooth muscle cells of coronary vessels. No signs of Notch1 signaling activation (such as nuclear NICD localization) were detected in undamaged mice hearts. Acute myocardial infarction was accompanied by the increase in the total amount of c-kit + Notch1 + CSCs and the appearance of nuclear NICD localization in a number of CSCs showing an activation of Notch signaling. Cultivation of CSC in vitro on dishes coated with Jagged 1 ligand released NICD and activated expression of Notch target genes (Hes, Hey). Activation of Notch signaling upregulated expression of endothelial cell transcription factors Gata 4 and Vezf1 in CSCs but γ-secretase inhibitor prevented Notch signaling activation and endothelial cell commitment of CSCs. CONCLUSIONS: These results revealed that Notch signaling activation promote CSCs commitment toward vascular cells. These findings suggest that modulation of Notch signaling can be promising therapeutic strategy for the treatment of myocardial ischemic damage.