OBJECTIVE: Recently, we have shown that shear stress regulates the angiogenic potential of endothelial cells in vitro by an Angiopoietin-2 (Ang2)-dependent mechanism; however its pathophysiological significance in vivo was not clear. We hypothesized that Ang2 plays an important role in blood flow recovery after arterial occlusion in vivo by regulating angiogenesis and arteriogenesis. METHODS AND RESULTS: C57Bl/6J mice underwent femoral artery ligation and were injected with a specific Ang2 inhibitor, L1-10, or vehicle for 10 days. Ang2 mRNA was upregulated at day 2, and Ang2 protein was upregulated at day 2, 5, and 7 in the ligated hindlimb. L1-10 treatment significantly blunted blood flow recovery. L1-10 decreased smooth muscle cell coverage of neovessels without affecting capillary density, suggesting a specific role for Ang2 in arteriogenesis. Mechanistically, L1-10 decreased expression of intercellular and vascular cell adhesion molecules as well as infiltrating monocytes/macrophages in the ischemic tissue. Although L1-10 had no effect on the number of CD11b+ cells (monocytes/macrophages) mobilized in the bone marrow, it maintained elevated numbers of circulating CD11b+ cells in the peripheral blood. CONCLUSIONS: These results suggest that Ang2 induced in ischemic tissue plays a critical role in blood flow recovery by stimulating inflammation and arteriogenesis.