BACKGROUND:: In addition to the advantages of conventional lentiviral vectors, Tet-On lentiviral vectors can regulate the expression of target gene by doxycycline or similar analogue because of insertion of trans-acting factors. OBJECTIVE:: To investigate the effects of Tet-On lentiviral vectors carrying human bone morphologic protein 2 on transfection and osteogenesis of human umbilical cord mesenchymal stem cells (hUMSCs). METHODS:: The cultured passage 3 hUMSCs were divided into four groups. In the hUMSC + doxcycline group, cells were stably transfected with Tet-On lentiviral vectors carrying human bone morphologic protein 2 and 10 mg/L doxcycline was added. In the hUMSC group, cells were treated the same as the hUMSC + doxcycline group, with the exception of addition of doxcycline. In the empty virus group, cells were transfected by green fluorescence protein. In the blank control group, cells were not treated. RESULTS AND CONCLUSION:: Human bone morphologic protein 2 expression was significantly higher in the hUMSC + doxcycline group than that in the hUMSC group (P < 0.05). Human bone morphologic protein 2 expression was not detected in the empty virus and blank control groups. Alkaline phosphatase staining results showed that a large number of red or brown granules appeared in the cytoplasm in the hUMSC+ doxcycline group, and there were a few red or brown granules in the cytoplasm in the hUMSC group. Alkaline phosphatase activity was significantly higher in the hUMSC+ doxcycline group than in the hUMSC group (P < 0.05). Such red or brown granules were not observed in the empty virus and blank control groups. Tubercles developed in the hUMSC + doxcycline group and hUMSC group. The tubercles were more and larger in the hUMSC + doxcycline group compared with the hUMSC group. Tubercles were not observed in the empty virus and blank control groups. These findings suggest that Tet-On lentiviral vectors carrying human bone morphologic protein 2 can stably transfect human umbilical cord mesenchymal stem cells and significantly increase cellular osteogenic capability.Zhang Z, Tian SQ, Zhang CL,Sun K, Zhang JH, Sui AH, Zhou M, Feng XT. In vitro osteogenetic effects of the Tet-On lentiviral vectors carrying human bone morphologic protein 2 transfected human umbilical cord mesenchymal stem cells.Zhongguo Zuzhi Gongcheng Yanjiu. 2012;16(14): 2545-2549. [http://www.crter.cn http://en.zglckf.com]