Abstract: Objective To study the effect of endothelial progenitor cells (EPCs) expressing hypoxia inducible factor 1αmu on osteogenesis and angiogenesis of bone morphogenetic protein 2 transfected bone marrow stromal cells(BMSCs) .Methods BMSCs and EPCs were obtained and identified from rabbit bone marrow by density gradient centrifugation.To define the best ratio of EPCs and BMSCs,MTT assay was used to detect the proliferation of different proportion of BMSCs/EPCs.Experiment was divided into 6 groups according to different cells and genes transfected：group A：BMSCs ；group B：Adv-BMP2-BMSCs；group C：BMSCs plus EPCs；group D：Adv-BMP2-BMSCs plus EPCs；group E：BMSCs plus Adv-HIF1αmu-EPCs；group F：Adv-BMP2-BMSCs plus Adv-HIF1αmu-EPCs. Adv-HIF1αmu and Adv-BMP2 were respectively transfected into EPCs and BMSCs with the optimum multiplicity of infection (MOI).The expressions of BMP2 and HIF-1α proteins were detected by Western blot .The osteogenesis and angiogenesis potential of co-cultured cells were detected by alkaline phosphatase (ALP) activity and qRT-PCR.Result The co-culture proportion of BMSCs and EPCs was 1:1.Western blot showed that expression of BMP2 protein in groups of Adv-BMP2-BMSCs、BMSCs was higher than that in the groups of Adv-HIF1αmu EPCs and EPCs(P<0.05),expression of HIF-1α protein in group of Adv-HIF1αmuEPCs was higher than that in the groups of Adv-BMP2 -BMSCs、BMSCs and EPCs(P<0.05).Alkaline phosphatase activity and osteogenesis and angiogenesis related gene expression in group F were higher than that in other groups (P<0.05).Conclusion Adv-HIF1αmu EPCs co-cultured with Adv-BMP2 -BMSCs can promote osteogenesis and angiogenesis of Adv-BMP2-BMSCs.

Key words: mutant hypoxia inducible factor1α, endothelial progenitor cells, morphogenetic protein 2, Bone marrow stromal cells, Osteogenesis, Angiogenesis