Figure 1

Trafficking of EPCs to ischemic/tumor tissues as directed by major cytokine/chemokine expression. Endothelial progenitor cell homing from the bone marrow niche to sites of neovasculogenesis is dependent a cytokine/chemokine gradient. The cellular stress induced by ischemic and tumor tissue leads to the release of a number of pro-angiogenic factors, including VEGF. VEGF stimulation of stromal cells leads to an increase in eNOS and NO production, leading to MMP-9 secretion. MMP-9 then converts m-KitL to s-KitL aiding in the release of EPCs from bone marrow stromal cells. The EPCs then migrate toward the angiogenic gradient via chemokine receptors including CXCR-4 and VEGFR-2.