Effect Of Recombinant Human Parathyroid Hormone 1-34 On Mandibular Distraction Osteogenesis In The Rabbits.

Objective:To study the effect of rh PTH(1-34) on promoting bone formation on mandibular distraction osteogenesis(DO)in rabbits, so as to provide foundation for its clinical application of rh PTH(1-34) in the field of DO.Material and Methods:8 big-eared Japanese Rabbits( no sex limit,weights about 2.0-2.5Kg) were selected as experimental animals,which were randomly dividedinto the control group,the rh PTH(1-34)12.5μg/kg group, the rh PTH(1-34)25μg/kg group, and the rh PTH(1-34)50μg/kg group,with ten rabbits in each group. Their parts ahead next to premolar teeth and mental foramen area on the right side of the mandibulars were slited in order to establish unilateral mandibular distraction osteogenesis models.Distraction was started one week after surgery at the rate of 0.4mm/12 h, which continued for 10 days, extending mandibular by 8.0mm and followed by fixed period.The corresponding dose of rh PTH(1-34),dissolved in 2% heat inactivated standard rabbit serum 1 ml, was given at eight every day via subcutaneous injection to the experimental groups from the distraction period till the rabbits’ death whlie the control group was only given 2% heat inactivated standard rabbit serum 1 ml at the same time every day. Five rabbits from each group were executed at the first week and third week in fixed period respectively. Then the new bones in distraction region were selected as the specimens. The general observation, histology of HE staining and immunohistology of BMPs examination were performed with the results istical analyzed by the statistical software SPSS17.0 and the heart,liver and renal removedfor routine pathologic examination respectively.Result:1.The distraction osteogenesis models were established successfully. None of the rabbits were dead. The right side of mandibular extends by 8.0mm,and occlusal disorder could be observed in every rabbit.2.General observation: In the first week of the fixed period, new bone tissues of the experimental groups were better than those of the control group. As the dose increased, new bone became better. In the third week of the fixed period, every group obtained a hard texture, with the texture of experimental groups more smooth and dense than that of the control group.3. X-ray:In the first week of the fixed period,the osteotomy lines were clear in control group, and the boundaries of the bone were fuzzy in experimental groups. In the third week of the fixed period, the control group obtained some hard texture, the experimental groups had more bone trabecula.As the dose increased, new bone became better.4. The histology examination demonstrated that the formation rate of the bones in experimental group was faster and the bone were more mature. Among the groups the rh PTH(1-34)50μg/kg one was the best.5. Immunohistology examination: The result of bone histomorphometry illustrated that the light density of BMPS was distributed over osteoblast, fibroblast and chondrocyte. The positive expression of the control group of BMPs was stronger than that of the control group.6. There’s no obvious injury in the specimen of cardiac,hepatic and renal tissues.Conclusion:The rh PTH(1-34) can promote the formation of bones on mandibular distraction osteogenesis in rabbits.