Endothelial-monocyte–activating polypeptide II induces migration of endothelial progenitor cells via the chemokine receptor CXCR3

Objective Recruitment of endothelial progenitor cells to the sites of ischemia has recently been suggested as a mechanism of tissue repair. Here we address the hypothesis that the hypoxia-inducible full-length endothelial-monocyte-activating polypeptide II (EMAP II) provides a mechanism to recruit late outgrowth highly proliferating endothelial progenitor cells (EPCs). Materials and Methods We tested in a transwell migration assay EMAP II for its ability to induce migration of EPCs. Furthermore, we measured changes in cellular calcium levels in EPC to assess the ability of EMAP II to induce intracellular signaling. Finally, we employed neutralizing antibodies and binding competition studies in order to identify the receptor mediating these activities of EMAP II in EPCs. Results EMAP II elicits dose-dependent migration and intracellular calcium mobilization in EPCs. Functional blocking and binding studies with radiolabeled interferon-γ–induced protein (IP-10) indicate that EMAP II employs the CXCR3 receptor for these activities in EPCs. Indeed, EMAP II-induced migration of EPCs can be abolished by prior treatment of cells with anti-CXCR3 antibodies or with IP-10. Conclusions These data suggests a novel function for EMAP II and a hitherto undescribed role of the CXCR3 chemokine receptor in EPC recruitment.