Experimental Study Of RhTGF-β1 Combined With RhBMP-2 In Lumbar Transverse Process Fusion

PrefaceSpinal fusion is one of the most common ways to treat spinal diseases. Transverse process fusion is the frequently used spinal fusion method. Transverse process fusion using autologous bone is a frequently used method for achieving lumbar intersegmental arthrodesis. Using autologous bone is the " gold standard" in the field of bone grafting. However, the use of autograft is subject to limitations with regard to suitable harvest location and volume of graft is also responsible for significant complications in as many as 30% of patients. To decrease complications associated with autologous bone graft, considerable attention has been directed toward development of suitable biosynthetic bone graft substitutes.Recombinant human transforming growth factor β1 (rhTGF - β1) , recom-binant human bone morphogenetic protein - 2 ( rhBMP - 2 ) and fibrin glue (FG) are used to construct tissue engineering bone in our experiment and applied for rabbit lumbar transverse process fusion. Manual palpation, radiographic analysis, biomechanical test and histologic examination are used to check spinal fusion condition. To investigate the efficacy of bone formation and spinal fusion with FG combined with rhBMP -2 and rhTGF - β1.Methods1. The source of animals1 year old (weight 3-5 Kg) healthy Japanese rabbits (no female or male limited) , which are provided and raised by China Medical University.2. Animal models construction30 one - year - old rabbits are divided into 3 groups randomly: group rhTGF - pi/rhBMP -2/FG, group rhBMP -2/FG, group FG. Spinal fusion operation is taken: burnishing the cortex, revealing the marrow cavity of transverse process, putting the carrier onto the L5 - L6transverse process.3. Record of dataAll the animals are sacrificed after 6 weeks and take the spine specimens out. The examination of the specimens is carried out: 1) observing by eyes;2) manual palpation;3) radiographic observation;4 ) gray analysis;5 ) biomechanical test;6)histologic examination.ResultsWe can see connective mass between the left L5^L6 transverse processes of eight specimens in group rhTGF - pi/rhBMP -2/FG. 4 specimens of group rhBMP - 2/FG have connective mass. There is nothing between the left L5NL6 transverse processes of all the specimens in group FG.Manual palpation shows that fusion ratio of group rhTGF - pi/rhBMP -2/ FG is 80% . Radiographic observation shows fusion ratio of group rhTGF - pi/ rhBMP - 2/FG is 80%. There is no statistical difference between group rhTGF- pl/rhBMP -2/FG and rhBMP -2/FG. Manual palpation and Radiographic observation show there is no fusion specimens in group FG. CT scan and 3D -CT show there is continous bone mass between L5%L6 transverse processes of group rhTGF - pi/rhBMP -2/FG.Gray analysis shows bone density and area of the specimens in group rhTGF- pl/rhBMP -2/FG are significantly higher than other two groups.Biomechanical test shows fusion strength of the specimens in group rhTGF- pi/rhBMP -2/FG is significantly more superior than group rhBMP -2/FG.HE dyeing shows there are mature bone tissues in bone mass between transverse processes of the fusion specimens in group rhTGF — pi/rhBMP — 2/FG and rhBMP-2/FG.Masson dyeing shows collagen tissues are abundant in the trabecula of thespecimens in group rhTGF - pi/rhBMP -2/FG.DiscussionTissue engineering bone should contain three basic elements;a. osteoge-netic factors;b. the right carriers;c. mesenchymal stem cells.Bone morphogenetic protein ( BMPs) family is the most widely studied and applied factors. BMPs can induce mesenchymal stem cells to differentiate into osteoblast and form new bone by cartilaginous osteogenesis. Recombinant human bone morphogenetic protein —2 which was authorized by FDA is the only osteo-genetic factor for clinical application.Vivo studies indicate the presence of transforming growth factor beta protein and transforming growth factor beta gene expression in normal fracture healing, whereas exogenous transforming growth factor beta administration stimulates the recruitment and proliferation of osteoblasts in fracture healing. In vitro, TGF -(31 can accelerate the osteogenic differentiation of bone marrow stem cells.FG can become appropriate carrier because many advantages, such as good plasticity, adjustable clotting time, suitable degradation speed, etc.In the present study, transverse process fusion had easy surgery procedures and small injury to the animals, so complications such as death, infection and paralysis were rarely seen.In our experimental study, rhTGF — (31 combined with rhBMP —2 are used in lumbar transverse process fusion. Although there is not statistical difference between group rhTGF - pl/rhBMP -2/FG and group rhBMP -2/FG in the rate of spinal fusion, the former is better than the latter on bone formation density, area and biomechanical test. Further, group rhTGF - (31/rhBMP -2/FG is better than group FG on all the examination.ConclusionThe results in this study show that rhTGF - pi enhances the efficacy of bone formation and transverse process fusion of rhBMP - 2 .Meanwhile, fibrin glue was effective as a bone graft material when combined with rhBMP -2 and rhTGF - Bl.