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The aim of this Paper was to observe and visualize the changes in osteoblasts by electron microscopy during osteogenesis using tissue engineering technique.We also studied the feasibility of improving tissue vascularization of the engineered bone by using small intestine submucosa (SIS)as the scaffold.Bone mesenchyal stem cells (BMSCs)were isolated by gradient centrifugation method.Bone mesenchymal stem cells were seeded in the SIS,and the scaffold-cell constructs were cultured in vitro for 2 weeks.Small intestine submucosa without BMSCs served as control.Both SIS scaffolds were then implanted subcutaneously in the dorsa of athymic mice.The implants were harvested after in vivo incubation for 4,8 and 12 weeks.The changes in osteoblasts and vascularization were observed under a transmission electron microscope and a scanning electron microscope.The BMSCs grew quite well,differentiating on the surface of the SIS and secreting a great deal of extracellular matrices.The scaffold-cell constructs formed a lot of bone and blood vessels in vivo.The scaffold degraded after 12 weeks.No osteoblasts,but vascularization and fibroblasts were observed,in the control.The SIS can be used as a scaffold for constructing tissue-engineered bone as it can improve the formation of bone and vessels in vivo.