The BMP-Smad Signal Passageway During Orthodontic Tooth Movement In Rats

The process of orthodontics is the process of tooth movement through orthodontic force . When the periodontium is stressed, a series of responses and changes will occur.A lot of investigations have been performed about the effects of local factors on orthodontic tooth movement. Bone Morphogenectic Proteins(BMPs) has been shown to be correlative with remodeling of periodontal, especially bone remodeling . Recently, a lot of researches how that Smad proteins play a critical role in mediating BMP-induced signals from the cell surface to the nucleus . The purpose of this study was to investigate the expression of BMP-2 and Smad 1,4,5 in the periodontium remodeling of rats during experimental tooth movement through immunohistochemistry method. The results are as follow: 1. The Expression of Bone Morphogenetic Protein (BMP)2 inPeriodontal during of Rats Orthodontic tooth movement The maxillary 1st molar of 30 rats were mesially moved with 50g force produced by spring coil. The Expression of BMP2 in periodontal tissues were determined by immunohistochemistry during orthodontic tooth movement .The results showed :(1) the immunoreactivities of BMP2were intensly stained in tensed zone of periodontium ,while the pressure zone was poorly stained. BMP2 was mostly located in normal periodontal tissues, especially near the alveolar bone or cementum . (2)At day 5, the immunoreactivities of BMP2 were strong positive . The results suggested that BMP2 participates bone absorption and remodeling in orthodontic tooth movement and play an important role. 2. The Expression of Smadl, 4 ,5 in rats during experimental orthodontic tooth movementBy immunohistochemistry method we found that Smad1,4,5 were weak immunopositive in normal periodontal tissues. The expression of Smadl ,4, 5 were immunoposotive in tensed zone during orthodontic tooth movement, which was similar to BMP. Osteoblasts and fibroblasts were observed immunpositive. At 5d groups, the immunoreactivities of Smadl were strong positive. But the expression of Smad4 were significantly altered during tooth movement. It was shown that Smad 1,4,5 were effectors of BMP signaling during bone remodeling. The results provide exidences for the molecular mechanism of BMPs action during bone remodeling.