Essential role of copper-zinc superoxide dismutase for ischemia-induced neovascularization via modulation of bone marrow-derived endothelial progenitor cells.

OBJECTIVE To investigate the effect of oxidative stress on ischemia-induced neovascularization in copper-zinc (CuZn) superoxide dismutase (SOD)-deficient mice. METHODS AND RESULTS In the vascular wall, CuZnSOD is essential for protecting against excessive oxidative stress and maintaining endothelial function. However, its specific role for the development of new vessels in response to ischemia is unknown. After surgically induced hind limb ischemia, CuZnSOD-deficient mice showed impaired neovascularization, as assessed by blood flow recuperation (laser Doppler) and capillary density in the ischemic muscles. This was associated with increased levels of oxidative stress in ischemic tissues and peripheral blood, together with reduced plasmatic NO production. CuZnSOD-deficient mice demonstrated an important reduction in the number of endothelial progenitor cells (EPCs) in the bone marrow and spleen. Moreover, EPCs isolated from CuZnSOD-deficient mice showed increased oxidative stress levels, decreased NO production, and a reduced ability to migrate and integrate into capillary-like networks. Importantly, the functional activities of CuZnSOD-deficient EPCs were rescued after treatment with the SOD-mimetic Tempol (a membrane-permeable radical scavenger) or the NO donor sodium nitroprusside (SNP). Moreover, the neovascularization defect in CuZnSOD-deficient mice could be rescued by wild-type (but not CuZnSOD-deficient) EPC supplementation. CONCLUSIONS Protection against oxidative stress by CuZnSOD may be essential for EPC function and reparative neovascularization after ischemia.