Background:
Angiogenesis is enhanced in the ischemic tissues after the injection of bone marrow cells (BMCs). However the exact mechanisms for this are not yet fully understood.
Methods:
A unilateral ischemic limb was surgically induced in mice and then BMCs were injected into the ischemic area. We measured the capillary/muscle ratio. Fluorescence-labeled BMCs were injected into the ischemic tissues and then the locations of the cells were examined by using a confocal microscope. Recruitment of bone marrow-derived cells into the ischemic tissue was examined in a sex-mismatched bone marrow transplantation (BMT) setting by identifying the Y chromosome with using the FISH technique. The expressions of VEGF, MMP-9, SDF-1 and CXCR-4 were measured by Western blot analysis.
Results:
The capillary/muscle ratio was more increased in the BMC-injected group than in the control group (P＜0.05). Florescence-labeled BMCs, which had been directly injected into ischemic tissue, were not detected in the tissue. In the sex-mismatched bone marrow transplantation models, the ischemic tissues of the BMC-injected group recruited a much greater number of Y chromosome-positive bone marrow- derived cells, as compared to the control group. The expressions of VEGF and MMP-9 were increased after injection of BMCs. SDF-1 was expressed on the seventh day in the BMC-injected group and CXCR-4 was highly expressed until 12 weeks in the BMC-injected group.
Conclusion:
We suggest that the injection of BMCs into ischemic tissue recruits CXCR-4-positvie cells from the bone marrow via the up-regulation of VEGF, MMP-9 and SDF-1, and these CXCR-4-positive cells may play a role in neovascularization.

Keywords: Ischemia, Angiogenesis, Bone marrow cell, VEGF, MMP-9, SDF-1, CXCR-4