TGF-β1 Stimulates Bone Resorption during Orthodontic Tooth Movement

BACKGROUND: Transforming growth factor（TGF）-β, which controls bone metabolism, is an important protein network. However, the relationship TGF-β and bone metabolism during orthodontic treatment of tooth movement is not well elucidated. PURPOSE: This study aimed to observe TGF-β1 expression on the compressed side of the periodontal tissue by moving rat teeth with orthodontic force in an animal experiment. In vitro, the change in TGF-β1 expression level when compression force（CF）was applied to human periodontal ligament（hPDL）cells was examined. MATERIAL AND METHODS: In vivo, 20 male rats were subjected to 10 g of orthodontic force for 7 days to move maxillary first molars in the mesial direction. Then, immunohistochemical analysis was performed to observe the expression of tartrate-resis-tant acid phosphatase（TRAP）and TGF-β1 protein in rat alveolar bone. In vitro, hPDL cells were used to study the effect of CF on TGF-β1 mRNA and protein expression. RESULTS: In vivo study, after 7 days, multinucleated cells and resorption lacunae were found on the surfaces of the alveolar bones in the 10-g group. Additionally, TGF-β1 immunoreactivity with orthodontic force was observed in the periodontal ligament （PDL）tissue on the 7th day. In vitro, TGF-β1 expression increased in the 1.0 g/cm² group compared to that in the control group in hPDL cells. CONCLUSION: Taken together, these results reveal that TGF-β1 expression is acti-vated in the periodontal tissue when optimal orthodontic force is applied. Moreover, it is possible that the TGF-β controls alveolar bone resorption during OTM.