Endothelial-specific CXCL12 regulates neovascularization during tissue repair and tumor progression.

C-X-C motif chemokine ligand 12 (CXCL12; Stromal Cell-Derived Factor 1 [SDF-1]), most notably known for its role in embryogenesis and hematopoiesis, has been implicated in tumor pathophysiology and neovascularization. However, its cell-specific role and mechanism of action have not been well characterized. Previous work by our group has demonstrated that hypoxia-inducible factor (HIF)-1 modulates downstream CXCL12 expression following ischemic tissue injury. By utilizing a conditional CXCL12 knockout murine model, we demonstrate that endothelial-specific deletion of CXCL12 (eKO) modulates ischemic tissue survival, altering tissue repair and tumor progression without affecting embryogenesis and morphogenesis. Loss of endothelial-specific CXCL12 disrupts critical endothelial-fibroblast crosstalk necessary for stromal growth and vascularization. Using murine parabiosis with novel transcriptomic technologies, we demonstrate that endothelial-specific CXCL12 signaling results in downstream recruitment of non-inflammatory circulating cells, defined by neovascularization modulating genes. These findings indicate an essential role for endothelial-specific CXCL12 expression during the neovascular response in tissue injury and tumor progression.