Smad7在兔下颌骨牵张成骨过程中的表达

Expression of Smad7 during mandibular alveolar distraction osteogenesis in rabbits

背景:有研究表明Smad7可结合并抑制骨形成蛋白受体的下游信号,而骨形成蛋白可促进牵张成骨过程中的骨愈合,并且Smad7对软骨形成起到抑制作用,但Smad7在牵张成骨中的作用机制尚不清楚。目的:利用种植型牵张器增高兔下颌牙槽嵴,观察下颌骨牵张成骨过程中Smad7的表达规律。方法:将雄性日本大耳白兔24只随机分为对照组4只,牵张成骨组20只,其中牵张成骨组再按牵张时间点不同再随机分为牵张成骨1d,1,2,4和6周组,4只/组。选取牵张成骨组兔左侧下颌骨行牵张成骨,其间歇4d,开始种植型牵张器垂直增高兔下颌牙槽嵴。各组分别于牵张成骨后1d,1,2,4,6周取材,在牵张成骨侧下颌骨行骨密度测量,用免疫组织化学法观察兔下颌骨牵张过程中不同时期Smad7的表达和分布。结果与结论:Smad7在正常下颌骨组织中有少量表达,在牵张后1d下颌骨中的Smad7表达高于对照组(P<0.05)。牵张成骨后1,2和4周组的Smad7表达比牵张成骨后1d组有所减少,但仍高于对照组,牵张成骨后6周时与对照组差异无显著性意义(P>0.05)。牵张区下颌骨骨密度值在牵张成骨后1d最低,1,2和4周组骨密度值相比对照组逐渐增高(P<0.01)。提示Smad7在牵张成骨过程的不同时期表达不同,Smad7可能对牵张成骨早期的新骨形成起一定的促进调节作用。

BACKGROUND： Some studies have shown that Smad7 can combine and inhibit downstream signals of bone morphogenetic protein receptor, and bone morphogenetic protein can promote the distraction osteogenesis in the process of bone healing, in addition, Smad7 plays an inhibitory effect on cartilage formation. However, the mechanisms of Smad7 in the process of distraction osteogenesis have not been reported. OBJECTIVE： To heighten the alveolar ridge of mandible using implant-distraction apparatus, and to investigate the law of Smad7 in distraction osteogenesis. METHODS： A total of 24 male Japanese white rabbits were randomly divided into blank control group （n = 4） and distraction group （n = 20）. In addition, the distraction group was divided into 1 day, 1, 2, 4, and 6 weeks subgroups, with 4 animals in each group. Distraction osteogenesis was performed on the left mandible of rabbits in the distraction groups with 4 days intervals, and the implant-distraction apparatus was used to increase in rabbit mandibular vertical alveolar ridge. The bone mineral density of mandible was measured at 1 day, 1, 2, 4 and 6 weeks after operation. The expression and distribution of Smad7 were observed by immunohistochemistry. RESULTS AND CONCLUSION： A sprinkle of Smad7 was expressed in normal mandible tissues. The expression of Smad7 was greater at 1 day after distraction than that of the control group （P 0.05）. The expression of Smad7 was gradually decreased at 1, 2 and 4 weeks after distraction, but remained greater than that of the control group. The difference between the 6 weeks group and the control group had no significance （P 0.05）. The bone mineral density of mandible reached a trough at 1 day after distraction, gradually increased in the 1, 2 and 4 weeks after distraction, which greater than that of the control group （P 0.01）. It is suggesting that the varied expression of Smad7 may promote the new bone formation at early stage of distraction osteogenesis.