Aim To investigate the effect and possible mechanism of bone marrow mesenchymal stem cells(BMSC)transplation on reparing injured vessels endothelium after carotid atherosclerosis stenosis angioplasty in rabbits.Methods Carotid atherosclemsis stenosis model of 48 rabbits had been successfully built up and randomly divided into BMSC transplantation group(n=24) and control group(n=24).BMSC were obtained by density gradient centrifugation and adherent cultured.Surface markers of BMSC were detected by flow cytometry,and BMSC pre-labled by DAPI.Balloon injured carotid artery of rabbits,meanwhile,BMSC(107/kg)were infused into injured artery of BMSC transplantation group rabbits by external carotid artery,and control group infused the same amount of PBS solution.The peripheral blood was collected and the vascular endothelial growth factor(VEGF) levels was detected by enzyme linked immunosorbent assay(ELISA) at preoperative and 3,7,14,28 days of BMSC transplantation.7 days after BMSC transplantation,DAPI labeled BMSC were detected by immunofluorescence microscopy.14 days after BMSC transplantation,the immunohistochemical staining was used to analyse platelet-endothelial cell adhesion molecule(CD31)expression in the injured vessels.28 days after BMSC transplantation,the neointimal area,the ratio of the intima/media area and vascular restenosis were analysed in the vascular tissue by hematoxylin and eosin staining.Results The expression of VEGF in BMSC transplantation group were elevated significantly compared with control group at 3,7,14,28 days after BMSC transplantation.7 days after BMSC transplantation,DAPI labeled BMSC were detected in injured vessels intima.14 days after BMSC transplantation,CD31 continues to express in intima of BMSC transplantation group,while the control group did not express CD31.The neointimal area(0.092 ± 0.009 vs 0.189 ± 0.007,P<0.01),the ratio of the intima/media area(0.698 ± 1.570 vs 1.630 ± 0.122,P<0.01) and the luminal stenosis ratio(41.70% ± 3.70% vs 61.28% ± 1.57%,P<0.01) were significantly decreased in BMSC transplantation group compared with control group at 28 days.Conclusion BMSC transplantation can promote repairing of endothelial after atherosclerotic stenosis carotid artery by balloon injury and reduce the restenosis of injured vessels.