079 MMP 9 Mediates Angiopoietin‐1 Recruitment of Endothelial Progenitor Cells to Diabetic Wounds

Introduction: Adenoviral gene transfer of Angiopoietin-1 (AdAng1) recruits endothelial progenitor cells (EPCs) and improves diabetic wound healing. A suggested mechanism for EPC mobilization from the bone marrow (BM) is mediated through MMP-9 and stem cell factor (SCF). We hypothesize that Ang-1 recruits EPCs to diabetic wounds via an MMP-9 dependent mechanism. Methods: Lethally irradiated mice were reconstituted with BM from transgenic TIE-2/LacZ mice. After engraftment, diabetes was induced with steptozotocin. 8 mm wounds were created in BM transplanted (BMT)(n = 12) or MMP-9 knockout (KO)(n = 12) mice and treated with 1 × 108 PFU of AdAng1, AdGFP or PBS. At 7 days wounds were analyzed for epithelial gap, vessel density, and EPCs. Serum levels of VEGF, proMMP9 and SCF were assessed. Data are expressed as mean ± SEM Results: In diabetic BMT wounds, AdAng1 results in improved reepithelialization (Ang1 2.3 ± .2 mm; GFP 3.9 ± .2; PBS 4.0 ± .1 p < .0001) neovascularization (Ang1 6.8 ± .3Caps/Hpf; GFP 3.0 ± .4; PBS 2.9 ± .3 p < .0001) and EPC recruitment (Ang1 5.3 ± .4 EPCs/Hpf; GFP 2.1 ± .3; PBS 2.2 ± .3 p < .0001). AdAng1 treatment results in increased levels of proMMP-9 (Ang1 9.7 ± .8 ng/ml; GFP 6.3 ± .9; PBS 6.4 ± .4 p < .01) and SCF (Ang1 265 ± 28 pg/ml; GFP 119 ± 16; PBS159 ± 12 p < .001). In MMP9 KO mice, AdAng1 accelerates reepithelialization (Ang1 3.2 ± .1 mm; GFP 4.1 ± .2; PBS 3.8 ± .2; p<.) but has no significant effect on neovascularization (Ang1 4.1 ± .5 Caps/HPF; GFP 3.9 ± .4; PBS 3.9 ± .6), EPC recruitment (Ang1 2 ± .3 EPC/Hpf; GFP 1.5 ± .3; PBS 1.6 ± .2) or SCF levels (Ang1 83 ± 5 pg/ml; GFP 83 ± 2; PBS 88 ± 6). Conclusions: The effects of Ang-1 on EPC recruitment and neovascularization are dependent on MMP-9. Our data support the hypothesis that MMP-9 enables SCF to permit mobilization of EPCs.