β-catenin在大鼠前腭缝牵张成骨中的表达

Expression of β-catenin during premaxillary suture distraction osteogenesis in rat

目的:β-catenin作为一种胞质内的糖蛋白,参与调节成骨细胞形成和骨骼发育。本实验观察β-catenin在大鼠前腭缝牵张成骨过程中的表达并探讨其作用。方法:将32只35天龄雌性SD大鼠随机分为实验组(n=20)和对照组(n=12)。实验组大鼠在上颌切牙上安放扩大簧,牵张前腭缝,对照组动物不加力,2组动物均在牵张骨缝1、3、5、7d的相同时间取前腭缝标本。采用甲苯胺蓝染色观察前腭缝成骨细胞的形态和分布,免疫组织化学染色检测β-catenin和骨桥蛋白(osteopontin,OPN)的表达。结果:在未牵张的前腭缝,成骨细胞沿着骨缝两侧稀疏排列,β-catenin主要在成骨细胞的细胞膜上表达。牵张1d后,前腭缝扩大,成骨细胞在骨缝两侧聚集分布,大部分细胞呈β-catenin和OPN阳性,β-catenin在成骨细胞的细胞膜和细胞质中均有表达,其表达量高于对照组;牵张3d后,骨缝边缘有明显类骨质沉积,大量细胞质呈β-catenin强阳性的成骨细胞积聚成树突状指向骨缝中央,而OPN在这些成骨细胞中表达较弱;牵张5d后,新骨呈树突状大量形成,β-catenin表达减弱,OPN则在新骨基质及埋在期间的成骨细胞内大量表达;7d后大片新骨形成,骨缝变窄。结论:上颌骨缝牵张成骨过程中,β-catenin在成骨细胞中表达,其表达量与表达部位和成骨细胞的成熟相关,提示β-catenin参与了成骨细胞分化的调节。

PURPOSE： β-catenin, as a glycoprotein in cytoplasm, was involved in osteoblast development and bone formation. This study was designed to observe the spacial and temporal expression of β-catenin during premaxillary suture distraction osteogenesis in rat. METHODS： Thirty two female SD rats were randomly allotted into experimental group （n=20） and control group （n=12）. The experimental animals were subjected to premaxillary suture distraction by helix springs. They were sacrificed on the day 1, 3, 5 and 7. Toluidine blue staining was used to observe the morphology and distribution of the osteoblasts. The expression of β-catenin and osteopontin （OPN） was identified by immunohistochemical staining. RESULTS： During nature growth, osteoblasts were sparsely lining along the premaxillary suture. β -catenin immunostaining was mainly localized in the membrane of these cells. The width of the suture was enlarged 1 day after distraction and osteoblasts were accumulated along the suture. Most of these osteoblasts showed positive OPN and β- catenin immunostaining. β-catenin signals were expressed additionally in the cytoplasm of the osteoblast and were more intensive in experimental sutures than those in control animals. New bone deposition was identified on the day 3 after suture distraction. Clusters of osteoblasts with weak OPN staining and strong β -catenin signals in cytoplasm were projected into the suture. On the day 5, the level of β-catenin expression began to decrease while intensive OPN staining was observed in the finger-shaped trabecular bone and those osteoblasts embedded in it. New bone formation waswidespread in the expanded suture on the day 7. CONCLUSION： The expression level of β-catenin and the transition of the signals from membrane to cytoplasm along with the osteoblast maturation suggest that β-catenin might be involved in the regulation of osteoblast differentiation during premaxillary suture distraction osteogenesis in rat. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality （Grant No. 08DZ2271100 10QH1401600）, Shanghai Leading Academic Discipline Project （Grant No. S30206） and Research Fund of Shanghai Municipal Education Commission （Grant No. 09YZ75）.