Effect Of CpG ODN BW006 On Periodontal Tissue Remodeling In Rats With Experimental Tooth Movement

Orthodontic tooth movement is realized by the continuous reconstruction of periodontal tissue under mechanical load,how to regulate periodontal tissue remodeling more safely,stably,efficiently and accurately is of great significance to control orthodontic tooth movement.Previous studies have mostly focused on the effect of bone metabolic system on orthodontic tooth movement.With the continuous development of osteoimmunology,this concept has also been introduced into the field of orthodontics.Mechanical loading can induce aseptic inflammation through the immune process mediated by the activation of related immune cells,which in turn affects the process of periodontal tissue remodeling.Recent studies have found that CpG ODN can change the balance between bone and immune system during inflammation.Previous studies in vitro have confirmed that CpG ODN BW006 can promote the proliferation of rat osteoblasts.On this basis,this study intends to further explore the effect of CpG ODN BW006 on periodontal tissue remodeling in vivo and lay a foundation for further study of the mechanism of periodontal tissue remodeling regulated by CpG ODN.Objective:By establishing the model of experimental tooth movement in rats,using the methods of imaging,histology,histochemistry,and molecular biology,to observe the effects of local injection of CpG ODN BW006 on the distance of tooth movement and the morphological changes of periodontal tissue in rats with experimental tooth movement,and to detect the expression levels of osteogenic related transcription factors and immune cytokines in periodontal tissue.To investigate the effect of CpG ODN BW006 on periodontal tissue remodeling in rats with experimental tooth movement.Methods:Fifty-four 7-week old male Wistar rats were used to establish animal models of orthodontic tooth movement and divided into 3 groups randomly: 3 d group,7 d group and 14 d group,with 18 rats in each group.The drug was injected through the buccal side of the gingival mucosa,and CpG ODN BW006 was locally injected at the left maxillary first molar of the rats as the experimental side,and PBS was injected at the same right side as the control side,once every 3 days,with a dose of 40 ?L each time.At 3,7,14 d after orthodontic treatment,the rats were sacrificed and the maxillary tissues containing the first molars were prepared.The distance of tooth movement was measured by Micro-CT scanning,the morphological changes of periodontal tissue were observed by HE staining,the expression of Runx2 and Osterix protein in periodontal tissue was detected by immunohistochemical staining,and the expression levels of IL-1,IL-6,and TNF-? in periodontal tissue were detected by RT-PCR.Results:1.The model of experimental tooth movement in rats was established successfully,and no obvious mucosal changes were observed at the injection site.2.The distance of tooth movement was measured by Micro-CT scanning: the results showed that there was no significant difference between the experimental side and the control side in the 3-day group(P > 0.05).The distances of tooth movement in experimental side were(0.155±0.024)mm and(0.217±0.022)mm,while they were(0.200±0.013)mm and(0.536±0.233)mm in control side at 7 d and 14 d;there were significantly differences between two groups(P < 0.05 or P < 0.01).3.The morphology of periodontal tissue was observed by HE staining: the results showed that the degree of bone resorption on the pressure side of the experimental side was slighter than that of the control side,a large number of osteoblasts could be seen on the tension side of the experimental side,and the alveolar bone fullness and height of the rats in experimental side were significantly higher than those in control side.4.The expression of Runx2 and Osterix was detected by immunohistochemical staining: the results showed that the expression levels of Runx2 and Osterix in the periodontal tissue of the rats in experimental side were significantly higher than those in control side at 3 d and 7 d(P < 0.05 or P < 0.01),and reached a peak on the 7 th day;the expression levels of Runx2 and Osterix in experimental side were decreased slightly on the 14 th day;but there were still significant differences compared with control side(P < 0.05 or P < 0.01).5.The expression of IL-1,IL-6,and TNF-? mRNA was detected by RT-PCR: the results showed that there was no significant difference in the expression of IL-1,IL-6,and TNF-? mRNA between the experimental side and the control side at 3 rd day(P > 0.05).The expression levels of IL-1,IL-6,and TNF-? mRNA in the experimental side were significantly lower than those in the control side at 7 th day and 14 th day(P < 0.01 or P < 0.001).Conclusion:CpG ODN BW006 can reduce the distance of tooth movement,inhibit alveolar bone resorption,increase the expression of Runx2 and Osterix in periodontal tissue,and down-regulate the expression of IL-1,IL-6,and TNF-? in periodontal tissue.It is preliminarily proved that CpG ODN BW006 may regulate the remodeling of periodontal tissue in experimental tooth movement model rats based on osteoimmunology by promoting osteogenic related transcription factors and inhibiting immune cytokines.