Reactive Oxygen Species Regulate Osteopontin Expression in a Murine Model of Postischemic Neovascularization

Objective-Previous findings from our laboratory demonstrated that neovascularization was impaired in osteopontin (OPN) knockout animals. However, the mechanisms responsible for the regulation of OPN expression in the setting of ischemia remain undefined. Therefore, we sought to determine whether OPN is upregulated in response to ischemia and hypothesized that hydrogen peroxide (H2O2) is a critical component of the signaling mechanism by which OPN expression is upregulated in response to ischemia in vivo. Methods and Results-To determine whether ischemic injury upregulates OPN, we used a murine model of hindlimb ischemia. Femoral artery ligation in C57BL/6 mice significantly increased OPN expression and H2O2 production. Infusion of C57BL/6 mice with polyethylene glycol-catalase (10 000 U/kg per day) or the use of transgenic mice with smooth muscle cell-specific catalase overexpression blunted ischemia-induced OPN, suggesting ischemia-induced OPN expression is H2O2-dependent. Decreased H2O2-mediated OPN blunted reperfusion and collateral formation in vivo. In contrast, the overexpression of OPN using lentivirus restored neovascularization. Conclusion-Scavenging H2O2 blocks ischemia-induced OPN expression, providing evidence that ischemia-induced OPN expression is H2O2 dependent. Decreased OPN expression impaired neovascularization, whereas overexpression of OPN increased angiogenesis, supporting our hypothesis that OPN is a critical mediator of postischemic neovascularization and a potential novel therapeutic target for inducing new vessel growth. (Arterioscler Thromb Vasc Biol. 2012;32:1383-1391.)