Abstract: Objective To investigate the effect of bone morphogenetic protein 4（BMP4）-modified signaling pathway on human late outgrowth endothelial progenitor cells（LEPC）-related endothelial repair and the underlying molecular mechanism. Methods In vitro,after a 7-day and 28-day culture,BMP4 expression was observed in human early endothelial progenitor cells（EEPC）and LEPC. After inhibiting BMP4 with short hairpin RNA（shRNA）-mediated knockdown or up-regulating BMP4 with gene transfer,the Id2 expression and LEPC capacities of migration and adhesion were investigated in vitro. In vivo endothelial repair ability of BMP4 induced LEPC-related endothelial repair in nude mice with carotid artery denudation injury was also examined. Results BMP4 expressed selectively much higher in LEPC than in EEPC（P＜0.01）. Moreover,inhibition of BMP4 with shRNA down-regulated BMP4 and Id2 expression（P＜0.01）,impaired in vitro LEPC capacities（P＜0.01）and decreased the repaired areas of injured carotid artery endothelial in nude mice（34±6）% vs（58±7）%,P＜0.01. Furthermore,BMP4 gene transfer remarkably activated BMP4-mediated signaling pathway,resulting in increasing Id2 expression（P＜0.01）,facilitating therapeutic endothelial repair capacity of LEPC in nude mice with carotid artery denudation injury（75±5）%vs（59±6）%,P＜0.01. Conclusion BMP4-related signaling pathway is essential for endothelial repair capacity of LEPC in human.