BMPs and related factors appearing in the mouse periodontal tissues due to orthodontic mechanical stress

While periodontal membrane has important functions for orthodontic mechanical stress, bone morphogenetic protein families (BMPs) show crucial roles on differentiation of osteoblasts. Since our studies revealed interesting findings on expression of these molecules, we investigated BMPs and its related factors by using immunohistochemical methods in the current study. Eight-week-old ddY mice were used as experimental animals. To add continuous mechanical stress on periodontal membrane, rubber dam sheet between maxillary molars was inserted by using Waldo method. Experimental conditions with a time range between 15 minutes to 3 hours after mechanical stress application were studied by immunohistochemistry. Immunohistochemistry was performed using primary antibodies for BMP-2, BMP-4, Smad, P-Smad and DAKO-envision kit, and color was developed by DAB. As results, BMPs and Smad expressions after mechanical stress were extremely weak positive in periodontal membrane in the control group. Positive reaction was detected in fibroblasts of periodontal membrane. In experimental group, enhancement of BMP-2, BMP-4, Smad and P-Smad expressions 15 minutes after mechanical stress was recognized in periodontal membrane of the tension side. Increase of the expressions continued till 3 hours after starting of mechanical stress. In the sample of 15 minutes, even in the compression side enhancement of the positive reaction of BMP and Smad was detected to some extent. However, the expressions disappeared after this time point. These results suggest that expression of BMPs increases at the tension side and BMP signaling has a role for shifting of the tension side to bone forming state after execution of mechanical stress.