| Background and objective:Distraction osteogenesis(DO)is a process that involves cutting and slowly separating bone to allow the bone healing process to fill in the gap to repair skeletal deformities in reconstructive surgery.This technique not only avoids wounds in the donor area,but also helps soft tissue extend at the same time.It provides a new idea for clinical problems that can not be solved by traditional methods.As an endogenous tissue engineering technique,it has become an important means to correct a variety of craniofacial deficits and bone defect deformities.It is one of the major advances in the field of craniomaxillofacial surgery for decades.With the development of DO clinical and experimental research,the understanding about the ways and characteristics of the bone regeneration,and the impact of peripheral nerve and muscle tissue,has been improved greatly.It is generally believed that the infiltration of the surrounding fibrous tissue into the distraction gap can cause a large accumulation of fibroblasts in the process of distraction osteogenesis,thereby reducing osteoblasts and affecting the quality of osteogenesis in the distraction gap.However,as a new organization of engineering technology,there is a lot waiting to be explored and researched in a variety of ways.Due to the long time required in the fixed period,the disadvantages such as the defects in the newly formed bones,the promotion and application of clinical usage has been limited.To explore the cell and molecular mechanism of DO bone regeneration,to find effective measures to overcome the shortcomings of distraction osteogenesis,to promote bone regeneration,and to shorten the treatment cycle,are important frontier subjects for both domestic and foreign scholars.Bone tissue is innervated.Studies have shown that neurons have the controlled effect on bone metabolism.Semaphorion 3A is a kind of protein produced by osteoblasts.Semaphorion 3A regulates osteoblast and osteoclast activitives and participates in sensory innervation.It can adjust bone remodeling either directly or indirectly.The role of Semaphorion3A in bone healing process during systemic treatment may also be achieved by other means,such as regulating platelets,stem cell physiological activities and so on.In summary,Semaphorion3A plays an important role in the remodeling stage of bone formation and is likely to be the milestone for bone disease treatment.After establishing the rabbit unilateral mandibular distraction osteogenesis in the animal model,researcher focuses on studying the effect of exogenous Semaphorion3A on the osteogenesis of distraction osteogenesis in this study so as to achieve the following aims:to promote the new bone formation and mineralization of the distraction osteogenesis;to provide a scientific basis for shortening the treatment cycle of distraction osteogenesis;and to lay the foundation for clinical application through objective data analysis.Methods:1.Establishment of animal model:select New Zealand white rabbits as experimental animals,5 to 6 months of age and 2 to 3 kg each,20 in all,gender of the rabbits was not taken into consideration.After injecting anesthesia with pentobarbital sodium in the vein near the rabbit ear,select the osteotomy site within about 1 cm between the lower incisors and the posterior teeth.The interal distraction device was then mounted.The rate of separation is determined as about 0.4mm per rotation.six days later,distraction was taken at a rate of 0.8mm a day(0.4mm at 10 a.m.and another 0.4mm at 8 p.m.)for ten days till the desired length 8mm is reached,distraction device was fixed at the end of the stretch?2.Effects of Semaphorion3A on bone formation:The experimental animals were randomly divided into A and B groups.Semaphorion3A(500 ?g/kg)was injected into the distraction gaps of the rabbits from group B on day 1,day 5 and day 10 while Group A was a blank control.Bone samples were obtained at the 2nd and 4th week of the fixed period.How the Semaphorion3A affect the bone formation during distraction osteogenesis was observed by X-ray and histomorphometry.3.Checking the effect:Use X-ray to examinate the bone mineral density the moment the mandibular sample was extracted from the rabbit.Each sample was made into HE stained discontinuous slices with a total number of 6 in all.The number,the thickness,and the arrangement of the trabecular bone,and the number and density of the osteoblasts were observed under light microscope.The histomorphometry of bone tissue was analyzed by image software.Eight discontinuous slices of each sample were measured and the average number was used as the measurement parameter of the sample.The number of the newly formed bone and trabecular bone thickness were used as the measurement parameters.4.Statistical analysis:Parameters for bone mineral density and bone morphometry in the distraction gap were expressed as mean ±standard deviation.Results were analyzed by SPSS 19.0 software using the Two-Sample T-Test.The P value less than 0.05 were considered to be significant statistically.Results:The animal models selected in this experiment were more tolerant to the operation with a 100%survival rate after surgery.There were different degrees of eccentricity after distraction surgery;while all rabbits' urine and diet are in good condition.X-ray imaging was used to detect the effect of bone mineralization.The animal models with the injection of Semaphorion 3A showed better mineralization and osteogenesis than that in control group.Bone mineral density and histomorphometric examination showed that the results in experimental group were significantly better than that in control group.Conclusion:X-ray and histomorphometry proved that Semaphorion3A could promote the formation and mineralization of the new bone in mandibular distraction osteogenesis,suggesting that Semaphorion3A is an effective means of promoting bone formation in mandibular distraction osteogenesis. |
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