Effects Of Icariin On Orthodontic Tooth Movement In Rats

With development of modern economy and improvement of the life level, the knowledge of the orthodontics popularizes gradually, more and more adults, even elders have come to require treatment to improve their living quality or beauty of their appearance in the past years. Osteoporosis is such closely related with the caducity that nearly all elders face such problems. Most of adults would choose some drugs to prevent or treat it. The kind of drugs treating osteoporosis would influence the bone remodeling of alveolar bone generally. Due to the lower price, less toxic and side effects, traditional Chinese medicine(TCM) attracts many patients in China. With the development of biotechnology and modernization of TCM, many active constituents of TCM have been isolated and identified, which made it possible to research the mechanism in molecular level. The experimental studies about the single active ingredient of TCM are gradually accepted by scholars at home or aboard. Enhance, TCM treating osteoporosis has been the topic in the past 20 years. In addition, since prostaglandin E2(PGE2) was applied in orthodontic tooth movement(OTM) in 1982, more and more drugs have been attempted to induce more efficient OTM, such as, vitamin D, parathyroid hormone(PTH). However, some obstacles prevent their popularity in clinical. Herba Epimedii has been a commonly used in Chinese medicine for treatment of osteoposis in China. In the present study, icariin, which is the major pharmacologically active flavonol diglycoside of Herba Epimedii, was used to evaluated its effect on OTM when systematic administration in rats. In this study, we set up experimental animal models of OTM on 48 Sprague-Dawley (SD) rats firstly. The difference of the periodontal tissue and alveolar bone histological changes were observed by light microscope between the two groups at different time. Furthermore, tartrate resistant acid phosphatase (TRAP)staining was conducted to evaluate the number of osteoclasts and immunohistochemisty straining was used to observe the expression of receptor activator of nuclear factor-κB ligand (RANKL) in the bone remodeling. The results suggested that OTM was induced by icariin. The possible cause was that icariin increased the remodeling of the alveolar bone because of its well-balanced effects on bone formation and resorption.Purpose:OTM is achieved through bone remodeling of the alveolar bone. Icariin is the active ingredient isolated from Herba Epimedii, a TCM commonly used for osteoporosis treatment. The purpose of the study is to explore the effect of icariin on OTM in vivo, and analyze the possible mechanism.Methods:48 SD rats weighing180～200g were selected and divided into two groups randomly:the control group and the experimental group. Rats in the experimental group were given 20 mg/kg/day icariin by intragastric administration, while the control group received the same volume solvent. All rats were placed a closed coil spring between their upper first molar and incisor, exerting a force of about 40 g to establish animal models of OTM. As the first molar moved mesially, a space between the first and second molar was created. The rats were sacrificed in batch on the 7th, 14th,21st and 28th days after orthodontic treatment. The amount of tooth movement was measured, and histomorphometric analysis based on slices from periodontium adjacent to the maxillary first molars were was used to observe new bone formation, bone resorption and quantify osteoclasts.Results: alveolar bone. Subsequently, bone resorption in the experimental group decreased. On the tension side, the periodontal membrane telangiectasia appeared and space of periodontium increased, osteoblasts appeared and new bone formed. The new bone in the experimental group is more than the control group.3.TRAP staining showed the obvious difference among the two groups. We found that, the number of osteoclasts was much more than that of the control group on day 7 (20.33±1.21;9.83±1.47; P<0.01), which peaked among the four icariin groups. And subsequently the number of osteoclasts decreased to the baseline level on day 14, where there was no significant differences between the two groups. Further more, the decline of the number of osteoclasts in the icariin group went on. Few osteoclasts could be found until day 28, which was less than the control group obviously (1.33±0.82; 4.50±1.05;P<0.05).4.In the immunohistochemical analysis of the slices of periodontium, the expression of RANKL was higher as time gone. On day7, the expression of RANKL reached a peak, and subsequently the expression went down. The expression in the control group was lower when compared with the experimental group. The results were consistent with the HE staining and TRAP staining.Conclusions:Icariin could inhibit the formation of osteoclast progenitors in hematopoietic tissues and the resorption function of activated osteoclasts directly. Moreover, icariin may make advanced effects on osteoclasts through osteoblasts indirectly. Icariin took advantages of coupling of bone formation and resorption in vivo, to promote the activity of osteoclasts through RANK/RANKL/OPG signaling pathway, resulting in accelerating tooth movement. The results suggested that icariin could promoted bone remodeling of alveolar bone and accelerated OTM in rats.