BACKGROUND: Osteogenic growth polypeptide (OGP) had clear effect on promoting osteoblast proliferation, differentiation and mature. OBJECTIVE: To explore the expression of OGP gene, which was transfected into rabbit bone marrow mesenchymal stem cells (BMSCs) and to evaluate the effects of OGP on differentiation of rabbit BMSCs. METHODS: pcDNA3.1-OGP was constructed using gene cloning and recombination techniques. Rabbit BMSCs were transfected with pcDNA3.1-OGP mediated by lipofectamine 2000. The transfection positive cell clones were selected with G418. The expression of OGP gene was detected using reverse transcription-polymerase chain reaction analysis on an mRNA level. Differentiation of pcDNA3.1-OGP transfected BMSCs into osteoblast lineage was observed. RESULTS AND CONCLUSION: The pcDNA3.1-OGP plasmid was constructed successful and OGP expression was detected in rabbit BMSCs. Hydroxyproline content was increased, and alkaline phosphatase activity was also increased. These indicate that pcDNA3.1-OGP transfected BMSCs expressed OGP, and could differentiate into osteoblast lineage.

BACKGROUND:Under the in vitro conditions of cell harvesting, culture, and transplantation, whether bone marrow stromal cells (BMSCs) can be effectively applied in local gene therapy remains unclear.OBJECTIVE: To construct a recombinant eukaryotic expression plasmid carrying human bone morphogenetic protein-7 (hBMP-7) gene, and to expect to enhance osteoinductive properties of rabbit BMSCs transfected.DESIGN, TIME AND SETTING: A cell-genomics in vitro observation was performed at the Laboratory of Scientific Research, Second Affiliated Hospital of Harbin Medical University between July 2006 and July 2007.MATERIALS: Human healthy fresh placental tissue was provided by the Department of Gynaecology and Obstetrics, Second Affiliated Hospital of Harbin Medical University. Written informed consent was obtained from the women. One healthy male New Zealand rabbit was provided by the Laboratory Animal Center, Harbin Medical University.METHODS: hBMP-7 gene was cloned from human placental tissue to construct a recombinant eukaryotic expression plasmid carrying hBMP-7 gene by conjugating with eukaryotic expression vector pcDNA3.1. BMSCs were isolated from rabbit bone marrow and cultured in vitro. Then they were divided into 3 groups: pcDNA3.1-hBMP-7-transfected, pcDNA3.1 -transfected, and untransfected. 5×106 BMSCs were inoculated into a 60 mm3 flask containing antibiotic-free medium 1 day prior to transfection.MAIN OUTCOME MEASURES: RT-PCR and immunohistochemistry were employed to detect hBMP-7 expression in BMSCs, alkaline phosphatase activity, hydroxypreline content, and osteocalcin production in each group. RESULTS: After 72-hour transfection, a 1.3 kb fragment was seen in the pcDNA3.1-hBMP-7-transfected group, showing brown granules in the endochylema, but not seen in the pcDNA3.14ransfected and untransfected groups. ALP activity in the pcDNA3.1-hBMP-7-transfected group significantly increased at 2 days after transfection, peeked at 8 days, and still increased at 10 days. At each time point, alkaline phosphatase activity, hydroxyproline content, and osteocalcin production were significantly higher in the pcDNA3.1-hBMP-7-transfected group than in the pcDNA3.1 -transfected and untransfected groups (P<0.05 or P<0.01).CONCLUSION: Recombinant eukaryotic expression vector pcDNA3.1- BMP-7 was constructed successfully. Results indicated that hBMP-7 was expressed in BMSCs sufficiently and was involved in inducing differentiation of BMSCs into osteoblasts. The method would provide substantial basement for hBMP-7 gene therapy.