Granulocyte colony‐stimulating factor promotes neovascularization by releasing vascular endothelial growth factor from neutrophils

Abstract

The granulocyte colony‐stimulating factor (G‐CSF) promotes angiogenesis. However, the exact mechanism is not known. We demonstrate that vascular endothelial growth factor (VEGF) was released by Gr‐1 + CD11b − neutrophils but not Gr‐1 − CD11b + monocytes prestimulated with G‐CSF in vitro and in vivo. Similarly, in vivo, concomitant with an increase in neutrophil numbers in circulation, G‐CSF augmented plasma VEGF level in vivo. Local G‐CSF administration into ischemic tissue increased capillary density and provided a functional vasculature and contributed to neovascularization of ischemic tissue. Blockade of the VEGF pathway abrogated G‐CSF‐induced angiogenesis. On the other hand, as we had shown previously, VEGF can induce endothelial progenitor cell (EPC) mobilization. Here, we show that G‐CSF also augmented the number of circulating VEGF receptor‐2 (VEGFR2) EPCs as compared with untreated controls. Blocking the VEGF/VEGFR1, but to a much lesser extent, the VEGF/VEGFR2 pathway in G‐CSF‐treated animals delayed tissue revascularization in a hindlimb model. These data clearly show that G‐CSF modulates angiogenesis by increasing myelomonocytic cells (VEGFR1 + neutrophils) and their release of VEGF. Our results indicated that administration of G‐CSF into ischemic tissue provides a novel and safe therapeutic strategy to improve neovascularization.