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

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 l, 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 was widespread 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 & 10QHI401600), Shanghai Leading Academic Discipline Project (Grant No. $30206) and Research Fund of Shanghai Municipal Education Commission (Grant No. 09YZ75). [ABSTRACT FROM AUTHOR]