Immunohistochemical expression of osterix appearing in the mouse orthodontic periodontal tension sides

Early changes of Osterix expression were examined by immunohistochemistry (IHC) and fluorescent immunohistochemistry (FIHC) in mouse periodontal ligament exposed to experimentally induced orthodontic mechanical stress. Eight-week-old ddY mice were used as experimental animals. To provide continuous orthodontic mechanical stress on the periodontal ligament, a rubber dam sheet was placed between the upper molars of the mice. At 20 min, 1 h, 3 h, 9 h and 24 h after the insertion, related parts of the animal tissues were evaluated by IHC and FIHC regarding Osterix and Runx2 expressions. In the 3-h and 9-h experimental groups, orthodontic tension sites reacted positively. The positive reactions became weak in the experimental group at 24-h. The results suggest that Osterix acts as one of the key factors of osteogenic cell differentiation, which expresses the following after the expression of Runx2, down-steam of Runx2.