Stromal cell-derived factor-1 enhances pro-angiogenic effect of granulocyte-colony stimulating factor

Abstract

Granulocyte colony-stimulating factor (G-CSF) mobilizes bone marrow mononuclear cells into the peripheral circulation. Stromal cell-derived factor-1 (SDF-1) enhances the homing of progenitor cells mobilized from the bone marrow and augments neovascularization in ischemic tissue. We hypothesize that SDF-1 will boost the pro-angiogenic effect of G-CSF. NIH 3T3 cells retrovirally transduced with SDF-1alpha gene (NIH 3T3/SDF-1) were used to deliver SDF-1 in vitro and in vivo. Endothelial progenitor cells (EPCs) co-cultured with NIH 3T3/SDF-1 cells using cell culture inserts migrated faster and were less apoptotic compared to those not exposed to SDF-1. NIH 3T3/SDF-1 (10(6) cells) were injected into the ischemic muscles immediately after resection of the left femoral artery and vein of C57BL/6J mice. G-CSF (25 mug/kg/day) was injected intraperitioneally daily for 3 days after surgery. Blood perfusion was examined using a laser Doppler perfusion imaging system. The perfusion ratio of ischemic/non-ischemic limb increased to 0.57+/-0.03 and 0.50+/-0.06 with the treatment of either SDF-1 or G-CSF only, respectively, 3 weeks after surgery, which was significantly higher than the saline-injected control group (0.41+/-0.01, P<0.05). Combined treatment with both SDF-1 and G-CSF resulted in an even better perfusion ratio of 0.69+/-0.08 (P<0.05 versus the single treatment groups). Mice were sacrificed 21 days after surgery. Immunostaining and Western blot assay of the tissue lysates showed that the injected NIH 3T3/SDF-1 survived and expressed SDF-1. CD34(+) cells were detected with immunostaining, capillary density was assessed with alkaline phosphatase staining, and the apoptosis of muscle cells was viewed using an in situ cell death detection kit. More CD34(+) cells, increased capillary density, and less apoptotic muscle cells were found in both G-CSF and SDF-1 treated group (P<0.05 versus other groups). Combination of G-CSF-mediated progenitor cell mobilization and SDF-1-mediated homing of EPCs promotes neovascularization in the ischemic limb and increases the recovery of blood perfusion.