Chemokine receptor CXCR7 mediates human endothelial progenitor cells survival, angiogenesis, but not proliferation

Stromal cell-derived factor 1 (SDF-1) is a critical regulator of endothelial progenitor cells (EPCs) mediated physiological and pathologic angiogenesis. It was considered to act via its unique receptor CXCR4 for a long time. CXCR7 is a second, recently identified receptor for SDF-1, and its role in human EPCs is unclear. In present study, CXCR7 was found to be scarcely expressed on the surface of human EPCs derived from cord blood, but considerable intracellular CXCR7 was detected, which differs from that on EPCs derived from rat bone marrow. CXCR7 failed to support SDF-1 induced human EPCs migration, proliferation, or nitric oxide (NO) production, but mediated human EPCs survival exclusively. Besides that, CXCR7 mediated EPCs tube formation along with CXCR4. Blocking CXCR7 with its antagonist CCX733 impaired SDF-1/CXCR4 induced EPCs adhesion to active HUVECs and trans-endothelial migration. Those results suggested that CXCR7 plays an important role in human cord blood derived EPCs in response to SDF-1.