pcDNA3-hBMP2转染兔骨髓基质细胞的体外表达及体内成骨能力

背景：能否通过病毒或者非病毒载体将骨形态发生蛋白2转导到骨髓基质细胞发挥成骨作用？目的：观察真核表达载体pcDNA3-hBMP2转染兔骨髓基质细胞后体外表达，同时将MSC转染后但未筛选兔骨髓基质细胞自体回植入肌组织，利用X线观察其成骨情况。设计、时间及地点：观察对比实验。实验于2004—11／2005-04在辽宁医学院骨科研究室完成。材料：6只成年新西兰大白兔，雌雄不拘，体质量2．0～3．0kg。BMP2抗体为美国Sanaka公司产品，pcDNA3-hBMP2由解放军第四军医大学生化教研室蒲勤教授提供，限制性内切酶购于大连宝生物工程有限公司。方法：从大肠杆菌提取超纯质粒pcDNA3-hBMP2，从成年兔股骨抽取骨髓，密度梯度分离法分离培养骨髓基质干细胞，将细胞分成4组；A组：pcDNA3-hBMP2转染进行G418筛选；B组：pcDNA3-hBMP2转染未用G418筛选；C组：给予pcDNA3空载体转染；D组：仅加入脂质体转染试剂Fugene 6。主要观察指标：①应用免疫组织化学法检测转染后瞬时表达。②应用免疫组织化学法检测细胞骨钙素表达，分别应用原位杂交法检测细胞Ⅰ型胶原表达。③转染2周后将B组细胞自体回植入兔后腿肌组织中，移植4周后应用X射线观察成骨情况。结果：①pcDNA3-hBMP2成功转染入骨髓基质干细胞内并100％瞬间表达BMP2。②基因转染4周后，A组细胞骨钙素及Ⅰ型胶原表达高于C组及D组。③B组细胞回植肌组织4周后，X射线可显示新骨形成。结论：pcDNA3-hBMP2能安全有效转染兔骨髓基质干细胞，通过其分泌物BMP2来作用诱导细胞加速分化为成骨细胞。

In vitro expression and in vivo osteogenic capability of pcDNA3-hBMP2-transfected marrow stromal cells in rabbits

BACKGROUND: Whether bone morphogenetic protein 2 (BMP-2) can be transduced into marrow stromal cells (MSCs) and produce osteogenic effects by viral or non-viral vector remains unclear? OBJECTIVE: To observe the expression of cultured rabbit MSCs transfected with pcDNA3-hBMP2 in vitro. Simultaneously, the MSCs were transfected but not screened and then transplanted into autologous muscle to investigate the osteogenic capability by X-ray. DESIGN, TIME AND SETTING: A controlled observation experiment was performed at the Department of Orthopedics, Liaoning Medical University between November 2004 and April 2005. MATERIALS: Six adult New Zealand rabbits, of either gender, weighing 2.0-3.0 kg, were included for this study. BMP2 antibody was the product of Sanaka Company, USA. pcDNA3-hBMP2 was provided by Professor Pu Qin from the Department of Biochemistry, Fourth Military Medical University of Chinese PLA). Restriction enzyme was purchased from Takara biotechnology (Dalian) CO., LTD., China. METHODS: Super-purified plasmid pcDNA3-hBMP2 was extracted from E. coli. Bone marrow was taken from the adult rabbit femur for harvesting MSCs by density gradient separation. The MSCs were divided into the following 4 groups: Group A, cells were transfected and screened by G418; Group B, cells were transfected by pcDNA3-hBMP2; Group C, cells were transfected by empty vector pcDNA3; Group D, only transfection reagent Fugene 6 was added.MAIN OUTCOME MEASURES: Transient BMP2 expression was analyzed by immunohistochemistry. Expression of osteocalcin and collagen I was examined by immunohistochemistry and in situ hybridization, respectively. Two weeks after transfection, MSCs from the group B were autologously transplanted into the muscle. Four weeks later, X-ray assay was used to observe bone formation.RESULTS: pcDNA3-hBMP2 was successfully transduced into MSCs and transiently expressed BMP2 100%. Four weeks after gene transfection, expression levels of osteocalcin and collagen I were significantly higher in the group A than in the groups C and D. X-ray results demonstrated new bone formation four weeks after MSCs transplanted into the muscle.CONCLUSION: pcDNA3-hBMP2 can safely and efficiently transfect MSCs and induce them to differentiate towards osteoblasts by secreting BMP2.