The Effect Of Bone Growth Factors On Distraction Osteogenesis

Distraction osteogenesis (DO) is a new technique for correction of the congenital craniofacial deformity and acquired bone defect. Comparing to the conventional orthognathic surgery techniques, DO is less invasive and no need for bone grafting. In addition, soft tissue simultaneous expansion may improve long-term stability. But there are still some defects, including long duration of treatment and complications of local infection and bone ununion of distraction gap. Therefore, the key problem of clinical work is to accelerate osteogenesis and shorten the course treatment. The experiment studied the expression of endogenous bone growth factors (BMP-2& TGF- β1) during mandibular lengthening and the effects of exogenous bone growth factors on distraction osteogenesis by the model of mandibular distraction osteogenesis in rabbits. The purpose is that the experiment provides bases to find an effective measure to accelerate bone regeneration during mandibular lengthening.In our study, we established an animal model for lengthening the mandibular by DO in rabbits. The new generation bone were studied by X ray and histology research. To study the expression of BMP-2 and TGF- β1 during the different stage on DO, we used immuno- -histochemistry and molecular biology technique. In addition, we studied the effect of BMP-2 and TGF- β1 on DO by X ray , SEM examination and bone histomorphometry. The main content is to discuss the effect of exogenous bone growth factors on new bone formation and the relationship of BMP-2 and TGF- β1 during the course of DO.The results show.1. The model of mandibular distraction osteogenesis in rabbits is created successfully.2. The positive expression of bone growth factors in distraction zone is observed during mandibular lengthening. Different bone growth factors express different intensities in different parts.3. Positive staining for BMP-2 was mainly observed in the mesenchymal cells and the active osteoblasts at the edge of new born trabecular bone. Their strongest expression was noted at 0th day after distraction. At the 28th day after distraction, only weak BMP-2 expression was detected in those cells.4. Staining for TGF- P i was localized in mesenchymal cells and osteoblasts, on 0th day after distraction, a marked increase in TGF- ￡ i expression was observed in the regenerated bone. On the 28th day, TGF- P i showed weak staining.5. The bone regeneration in group A was superior to that of group B and C after DO at the rate of lmm/d. There were no marked differences between group B andC.6. At the rate of 2mm/d , the new bone formation of group A and group C were superior to that of group B and D. Group C was superior to group A, and group B and D were no new bone formation at the rate of 3mm/d.As follow of the conclusion:1. BMP-2 and TGF- ￡ i appear to play an important role in bone regeneration after DO.2. Exogeneous BMP-2 can accelerate bone formation during DO in rabbits.3. Exogeneous TGF-13 j may have no beneficial effect on bone regeneration following mandibular osteodistraction in rabbits.4. There is a synergetic action between BMP-2 and TGF- P i on DO. Using the two bone growth factors at the same time is better than using one of them for new bone formation on DO.