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

Abstract

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.