Abstract 622: Mechanisms of Impairment of Ischemia-induced Angiogenesis and Vasculogenesis in MMP-2-Deficient Mice
Background: MMPs are implicated in the process of neovascularization. However, the decisive role for individual MMP in vessel formation is poorly understood.
Methods and Results: To study the putative role of MMP-2 in the ischemia-induced neovascularization, hindlimb ischemia model was applied to MMP-2+/+ and MMP-2−/ − mice (6 weeks: young, n= 206; 72 weeks: old, n= 64). Serial Laser Doppler blood-flow (LDBF) analysis revealed the recover of the ischemic-normal LDBF ratio in MMP-2−/ − young and old mice remained impaired throughout the follow-up period. At day 35, microangiography and anti-L-lectin immunohistostaining revealed poorer-developed collateral vessels and capillary formation in MMP-2−/ − mice with both old and young ages. Aortic-ring culture assay showed markedly impaired angiogenesis in MMP-2−/ − mice, which was partially recovered by supplementation of recombinant MMP-2 into culture medium. Interestingly, a tissue inhibitor of MMP-2 (1μg/mL) as well as MMPs inhibitor GM6001 (10 μmol/L) significantly inhibited its reaction but not cysteine protease inhibitor (20 μmol/L, E64) or serine protease inhibitor (2 mmol/L, PMSF). At day 7, plasma and ischemic tissues of levels of VEGF and FGF protein reduced in MMP-2−/ − mice. Flow cytometry showed that the numbers of CD31+c-kit+ EPC-like mononuclear cells (MCs) in peripheral blood markedly decreased in MMP-2−/ − young mice, although there was no significant difference for its number in bone marrow (BM) of young mice. CD31+c-kit+ EPC-like cells from MMP-2−/ −mice showed impaired proliferation compared from MMP-2+/+ mice. Transplantation of BM-derived MCs from MMP-2+/+ mice restored neovascularization in MMP-2−/ − young mice.
Conclusions: In a mouse femoral artery ligation model, endogenous MMP-2 contributes to the ischemia-induced neovascularization through EC migration/invasion, proliferation, and EPC mobilization.