Decreased Circulating Progenitor Cell Number and Failed Mechanisms of Stromal Cell-Derived Factor-1α Mediated Bone Marrow Mobilization Impair Diabetic Tissue Repair

OBJECTIVE--Progenitor cells (PCs) contribute to postnatal neovascularization and tissue repair. Here, we explore the mechanism contributing to decreased diabetic circulating PC number and propose a novel treatment to restore circulating PC number, peripheral neovascularization, and tissue healing. RESEARCH DESIGN AND METHODS--Cutaneous wounds were created on wild-type (C57BL/J6) and diabetic ([Lepr.sub.db/db]) mice. Blood and bone marrow PCs were collected at multiple time points. RESULTS--Significantly delayed wound closure in diabetic animals was associated with diminished circulating PC number (1.9-fold increase vs. 7.6-fold increase in [lin.sup.-]/[sca.sup.-][l.sup.+]/[ckit.sup.+] in wild-type mice; P < 0.01), despite adequate numbers of PCs in the bone marrow at baseline (14.4 ± 3.2% [lin.sup.-]/[ckit.sup.+]/[scal.sup.+] vs. 13.5 ± 2.8% in wild-type). Normal bone marrow PC mobilization in response to peripheral wounding occurred after a necessary switch in bone marrow stromal cell-derived factor-1α (SDF-1α) expression (40% reduction, P < 0.01). In contrast, a failed switch mechanism in diabetic bone marrow SDF-1α expression (2.8% reduction) resulted in impaired PC mobilization. Restoring the bone marrow SDF-1α switch (54% reduction, P < 0.01) with plerixafor (Mozobil, formerly known as AMD3100) increased circulating diabetic PC numbers (6.8 ± 2.0-fold increase in [lin.sup.-]/[ckit.sup.+], P < 0.05) and significantly improved diabetic wound closure compared with sham-treated controls (32.9 ± 5.0% vs. 11.9 ± 3% at day 7, P > 0.05; 73.0 ± 6.4% vs. 36.5 ± 7% at day 14, P < 0.05; and 88.0 ± 5.7% vs. 66.7 ± 5% at day 21, P > 0.05, respectively). CONCLUSIONS--Successful ischemia-induced bone marrow PC mobilization is mediated by a switch in bone marrow SDF-lα levels. In diabetes, this switch fails to occur. Plerixafor represents a potential therapeutic agent for improving ischemia-mediated pathology associated with diabetes by reducing bone marrow SDF-1α, restoring normal PC mobilization and tissue healing.