Effect Of CpG 2006 On Experimental Tooth Movement And Bone Remodeling In Rats

Orthodontics is a process of bone remodeling which is coordinated by osteoblasts,osteoblasts and osteoclasts.It is an acute to chronic aseptic inflammatory reaction with the participation of a variety of biological factors.So how to regulate the process of bone remodeling and then affect the process and effect of orthodontics is practical significant.ODN(oligodeoxynucleotides,ODN)is a kind of polynucleotide chain with less than 50 nucleotides,which has been widely studied in anti-tumor,infection,immunity and other aspects.Previous studies of our research group have proved that certain specific sequences of ODN have an effect on bone remodeling,and can inhibit bone resorption caused by periodontitis and affect the movement of orthodontic teeth in rats.We intend to use an ODN sequence named CpG 2006,which is widely used in the field of immunology,to carry out relevant studies,so as to verify the effects of ODN substances on the orthodontic tooth movement and bone remodeling in experimental rats.Objectives:Rat models of tooth movement were established and local injection of CpG 2006 was performed.To explore the influence of CpG 2006 on orthodontic tooth movement and bone reconstruction by measurement of the teeth movement distance,X-ray analysis,Real-time PCR techniques in the detection of periodontal tissue osteogenesis,osteoclasts,inflammation related factors,and HE staining on rat organs to test its biosafety to explore the experimental basis for further experiments.Study Design:Twenty-four male Wistar rats were selected to establish the maxillary tooth movement model.The left side was used as the experimental group,and CpG 2006 was locally injected into the buccal mucosa of the first molars.The right side was used as the control group,and the corresponding parts were injected with PBS.Dose of 40 mu L(25 mg/L)is injected every 3d,two groups of rats(12 4%paraformaldehyde heart perfusion+ 12 cervical dislocation)to be put to death 14 days later.The first 12 rats are taken the maxilla’s photographs,measuring the rat maxillary first molar mesial movement distance on both sides,and taking X ray films,taking the heart,liver,spleen,lung,kidney organs to HE staining to detect its biological safety.Total RNA was extracted from the maxillary bone tissue of the other 12 rats,and the reverse transcription was converted into cDNA.Real-time PCR technology was used to detect the osteoblasts,osteoclasts and inflammatory factors in the periodontal tissues.Result:Rat tooth movement model was successfully established.After 14 days,gross alveolar bone specimens of rats were observed by naked eyes.The movement distance of the maxillary first molar on the experimental side was significantly smaller than that on the control side.The height of alveolar bone around the first molar on both sides was not significantly reduced,and the clinical crown was not significantly changed.After measurement and analysis by Image J software,the movement distance of the experimental lateral teeth was 0.01420.0093mm,and that of the control lateral teeth was 0.4097 0.0261mm.The movement distance of the experimental lateral teeth was significantly smaller than that of the control side,and the difference was statistically significant(P<0.001).X-ray showed normal bone density of alveolar bone around the first molar on the exper:imental side,no obvious low-density bone resorption X-ray,and slightly widened periodontal space around the root.The periodontal space of the first molar on the control side was significantly widened,and the alveolar bone around the distal root was slightly less dense.Strength after 14 d,Runt in periodontal tissue of experimental side related transcription factor 2(Runt-related transcription factor 2,Runx2),zinc finger transcription factor(Special protein 7,SP7),osteocalcin(OCN,osteocalcin)mRNA expression levels were significantly higher than control(P<0.01),and with the SP7,OCN mRNA is most significant(P<0.001).Meanwhile,the mRNA expression levels of Interleukin 1(IL-1),Interleukin 6(IL-6),and Tumor necrosis factor alpha(TNF-alpha)in the periodontal tissues of the experimental side were lower than those in the control side(P<0.05),and the decreased mRNA levels of IL-1 and IL-6 were the most significant(P<0.001).The expressions of both Nfatc,CTSK and MMP9 mRNA in periodontal tissues showed no statistical significance.The HE sections of rat heart,liver,spleen,kidney and lung all showed the normal histological appearance of the corresponding organs.For example,the long axis of myocardial cells was arranged in a fibrous bundle,without vacuoles,edema or cell damage.Hepatocytes were arranged in a regular radial pattern around the vein.In the histological staining of spleen,the red and white pith were clear and the lymph nodules were evenly distributed.Monolayer columnar epithelial cells were seen in lung sections,and alveoli were intact without dilatation.The glomeruli,tubules and interstitium of renal tissue were normal.Conclusion:1.CpG 2006 can slow down the experimental tooth movement in rats,indicating that it affects the orthodontic bone remodeling process.2.CpG 2006 can up-regulate the expression levels of the osteogenic differentiation factors Runx2,SP7 and OCN mRNA in periodontal tissues during the process of experimental tooth movement,indicating that it can affect the bone remodeling process by promoting osteogenic activation.3.CpG 2006 can down-regulate the expression levels of inflammatory factors IL-1,IL-6 and TNF-a mRNA in periodontal tissues during the process of experimental tooth movement,proving that it can reduce the inflammatory response during tooth movement,thus affecting tooth movement.4.Local injection of CpG 2006 has no obvious pathological influence on the heart,liver,spleen,lung and kidney tissues of rats in a short period of time,indicating that it is of certain biological safety.