Aim To investigate the involvement of stromal cell-derived factor-1(SDF-1)/CXCR4 Axis in recruitment of endothelial progenitor cell(EPC)and reendotheliazation after vascular injury.Methods EPC migration induced by SDF-1α was determined with modified Boyden chamber assay.Treatment of mice after carotid injury with EPC or EPC coincubated with AMD3100(an antagonist of CXCR4),recruitment of EPC,reendotheliazation and neointimal lesion area were determined 14 d later.Results SDF-1α profoundly enhanced EPC migration(p<0.01),but could not enhance migration of EPC treated with AMD3100(p>0.05).Transfused EPC were strictly restricted to the injury site(14.2±3.6 cell/section),and lectin binding confirmed the endothelial phenotype,but only few EPC coincubated with AMD3100 were recruited to the injury site(4.0±2.5 cells/section).Treatment with EPC caused enhanced reendothelialization(83.45%±5.44%,p<0.01)associated with a reduction of neointima formation(19 237±1 875 μm2,p<0.01)compared with isotype control(66.46%±6.16%,34 676±2 412 μm2);treatment with EPC coincubated with AMD3100 caused no enhanced reendothelialization(68.02%±6.68%,p>0.05)and no reduction of neointima formation(32 451±2 081 μm2,p>0.05)compared with isotype control.Conclusions Stromal cell-derived factor-1/CXCR4 Axis plays an instrumental role in recruitment of EPC and reendotheliazation after vascular injury in mice.