Abstract-Peripheral blood (PB)-derived CD14ϩ monocytes were shown to transdifferentiate into endothelial cell (EC) lineage cells and contribute to neovascularization. We investigated whether bone marrow (BM)-or PB-derived CD34 Ϫ /CD14 ϩ cells are involved in reendothelialization after carotid balloon injury. Although neither hematopoietic nor mesenchymal stem cells were included in human BM-derived CD34 Ϫ /CD14 ϩ monocyte lineage cells (BM-MLCs), they expressed EC-specific markers (Tie2, CD31, VE-cadherin, and endoglin) to an extent identical to mature ECs. When BM-MLCs were cultured with vascular endothelial growth factors, hematopoietic markers were drastically decreased and new EC-specific markers (Flk and CD34) were induced. BM-MLCs were intra-arterially transplanted into balloon-injured arteries of athymic nude rats. When BM-MLCs were activated by monocyte chemoattractant protein-1 (MCP-1) in vivo or in vitro, they adhered onto injured endothelium, differentiated into EC-like cells by losing hematopoietic markers, and inhibited neointimal hyperplasia. Ability to prevent neointimal hyperplasia was more efficient than that of BM-derived CD34

Background-Although potential participation of bone marrow-derived circulating endothelial progenitor cells (EPCs) to neoangiogenesis has been proposed, the precise molecular mechanisms of EPC recruitment to vascular endothelium has not been fully elucidated. Methods and Results-Peripheral blood mononuclear cells were isolated from healthy volunteers and cultured for 7 days to obtain EPCs. Tumor necrosis factor-␣-activated human umbilical vein endothelial cells (HUVECs) supported significantly more rolling and adhesion of EPCs compared with inactivated HUVEC monolayer. Pretreatment of activated HUVEC with an adhesion-blocking mAb to E-selectin significantly reduced EPCs adhesion to HUVECs. When HUVECs were transduced with a recombinant adenovirus of E-selectin (AdRSVE-sel) or that of ␤-galactosidase (AdRSVLacZ), E-selectin-transduced but not LacZ-transduced HUVECs exhibited significantly more EPC rolling as well as adhesion. Further, effect of AdRSVE-sel or AdRSVLacZ was examined in mouse hind limb ischemic model. AdRSVE-sel-transduced mice showed significantly less limb necrosis and higher laser Doppler ratio when compared with AdRSVLacZ-transduced mice. Interestingly, blood flow recovery of ischemic limb observed in AdRSVE-seltransduced mice was more prominent when combined with EPC administration compared with that of AdRSVLacZtransduced mice. Conclusions-Endothelial E-selectin plays a crucial role in EPC-endothelial interaction in vitro. The importance of E-selectin was also confirmed in vivo even in the absence of exogenous EPC. These data provide molecular background for novel cell-based therapy for ischemic atherosclerosis.