Knock down of E-selectin by in vivo administration of E-selectin siRNA impaired vasculogenesis of ischemic hindlimb, which was rescued by sE-selectin treatment. (A) Real-time RT-PCR showed that E-selectin siRNA significantly attenuated the expression of E-selectin in various tissues after ischemia, especially in ischemic muscle, when the mice were treated with E-selectin siRNA (†P < .05; n = 4). (B-D) A million EPCs cultured from bone marrow of eGFP transgenic mice (green) were transplanted into siRNA-treated mice after induction of ischemic hindlimb. Before EPC transplantation, either BSA or sE-selectin (sE-sel) was injected into ischemic muscle. (B) Representative fluorescent images of muscle 1 week after ischemia (scale bar, 100 μm). BS-1 lectin staining (red) was used for visualizing ECs. (C) Quantitative analysis of incorporated EPCs to ischemic limb. The number of homing EPCs to ischemic limb was markedly decreased by E-selectin siRNA, but not by control siRNA (†P < .05). Injecting sE-selectin recovered EPC homing in E-selectin siRNA-treated mice (†P < .05). (D) LDPI analysis of siRNA-treated mice. Compared with control animals treated with control siRNA + BSA (red circle), the animals treated with E-selectin siRNA + BSA (blue triangle) showed significantly attenuated blood flow recovery to ischemic limb. But administration of sE-selectin (black square) was able to rescue the impaired blood flow recovery to ischemic limb in E-selectin siRNA-treated animals (blue triangle) (†P < .05; n = 7, respectively). Error bars in panels A, C, and D represent SD.