Objective To detect the changes of number and function of endothelial progenitor cells (EPCs) in gld.apoE-/-C57BL/6 mice,and to investigate whether premature atherosclerosis of gld.apoE-/-C57BL/6 mice was mediated by the dysfunction of these EPCs.Methods EPCs were isolated from peripheral blood and bone marrow of four types of C57BL/6 female mice:gld+/+apoE+/+,gld,apoE-/-and gld.apoE-/-.The percentage of EPCs was analyzed by FACS as CD11b-Sca-1+CD309+ cells.The attached cells were stained with DiI labeled acetylated low-density lipoprotein (DiI-ac-LDL) and FITC-labeled Ulex Europaeus agglutinin 1 (FITC-UEA-1) double staining to determine their phagocytic function.The adherent function of EPCs was determined by calculating the number of re-cultured EPCs.The capacity of EPCs to form the cavity structure was detected by calculating the number of the formed vascular-like structure.Results The percentage of circulating EPCs was significantly decreased in the gld.apoE-/-group (0.012±0.002)％ compared to the gld+/+ apoE+/+ group [(0.039±0.005)％,P＜0.01],the gld group [(0.025±0.001)％,P＜0.05],and the apoE-/-group [(0.028±0.002)％,P＜0.01].The percentage of bone marrow derived EPCs was decreased in the gld.apoE-/-group (0.12±0.01)％ compared to the gld+/+apoE+/+ group [(0.42±0.05)％,P＜0.05].The percentage of DiI-acLDL and FITC-UEA-1 double positive cells was decreased in the gld.apoE-/-group [(59.2±2.1)％] compared to the gld+/+apoE+/+ group [(87.5±3.0)％,P＜0.01],and the gld group [(84.2±6.0)％,P＜0.01] ; the adherent function of EPCs was impaired in the gld.apoE-/-group [(50.0±5.3)％] compared to the gld+/+ apoE+/+ group [(86.0±7.3)％,P＜0.01],the gld group [(73.0±1.0)％,P＜0.01],and the apoE-/-group [(65.0±4.0)％,P＜0.05] respectively.The capacity of EPCs to form the cavity structure was decreased in the gld.apoE-/-group (4.0±0.3) compared to the gld+/+apoE+/+ group (12.0±1.4,P＜0.01).Conclusion The number of EPCs is decreased in the gld apoE-/-C57BL/6 mice,the adhesion,phagocytosis and angiogenic function of EPCs in the bone marrow are impaired,which may be one of the causes of lupus with atherosclerosis.