Abstract 774: Decreased Number And Functional Activities Of Endothelial Progenitor Cells In CuZnSOD-deficient Mice.
Background: Several risk factors for cardiovascular diseases are associated with reduced neovascularization in response to ischemia. A common feature of all cardiovascular risk factors is increased production of reactive oxygen species (ROS) such as superoxide. We have recently demonstrated that mice that are deficient for CuZnSOD present impaired neovascularization in response to ischemia. Here we tested the hypothesis that endothelial progenitor cell (EPC) dysfunction might be involved in this neovascularization defect.
Methods and results: Seven days after surgically induced hindlimb ischemia, EPCs were isolated from CuZnSOD deficient mice (CuZnSOD−/ −, n=8 –10) or control mice (CuZnSOD+/+, n=8 –10). We found that the number of EPCs was significantly reduced in the bone marrow (40.6±3.0 vs 70.5±5.0, p<0.05) and the spleen (0.29±0.06 vs 0.54±0.11, p<0.001) of CuZnSOD−/ − mice compared to controls. Moreover, EPC functional activities were significantly impaired in CuZnSOD−/ − mice. More specifically, we found that EPC adhesion was reduced by 41%, migration by 88%, proliferation by 46% and integration into tubules by 77% in CuZnSOD−/ − mice. To confirm the role of EPCs in vivo, we isolated CD117+ cells (also acLDL and lectin positive when cultured for 4 days in vitro) from the bone marrow of CuZnSOD +/+ mice and performed an intravenous injection (5X105 cells) into CuZnSOD −/ − mice at 24 hours after surgically-induced hindlimb ischemia. Interestingly, EPC supplementation in CuZnSOD−/ − mice led to a complete rescue of ischemia-induced neovascularization, as assessed by blood flow recuperation in the ischemic hindlimb (Laser-Doppler analysis). Moreover, EPC therapy in CuZnSOD−/ − mice was also associated with a significant reduction of oxidative stress in ischemic tissues (nitrotyrosine and DHE staining).
Conclusions: CuZnSOD deficiency is associated with a significant reduction in the number and the functional activities of EPCs. Cellular therapy with EPC can rescue the impaired neovascularization in CuZnSOD−/ − mice. Our results suggest that increased oxidative stress could contribute to explain EPC dysfunction and impaired neovascularization associated with different cardiovascular risk factors.