Cross-regulation Of NF-κB And Wnt/β-catenin Pathway On Distraction Osteogenesis Of Premaxillary Suture In Young Adult Rats

ObjectiveThe purpose of this study was to observe the changes of osteogenic tissue and osteogenic factors in premaxillary suture by local injection of β-catenin agonist after expansion of premaxillary suture in rats,and to explore the cross-regulation of NF-κB and Wnt/β-catenin pathway on distraction osteogenesis in premaxillary suture of rats,effect on proliferation and differentiation of osteoblasts and formation of new bone.Therefore,the application of drugs in RME can promote the reconstruction of premaxillary suture,and reduce risk of the relapse after RME,and shorten the retention time after orthodontic treatment,thus providing a certain experimental basis for the clinical orthodontic treatment.Materials and MethodsForty-five eight-week-old healthy male SD rats were randomly divided into three groups: group A,group B and group C,with 15 rats in each group.The rats in each group were fed in cages with 5 rats in each cage.Rats in the control group(group A)received neither rapid maxillary arch expansion nor premaxillary suture injection of β-catenin agonist(only the same dose of DMSO);Rats in group B were treated with rapid maxillary arch expansion without injection of β-catenin agonist into premaxillary suture(with the same dose of DMSO only).Rats in group C were treated with maxillary expansion and β-catenin agonist was injected into premaxillary suture daily.Rats in the expansion group were anesthetized with 10% chloral hydrate(4ml/kg)intraperitoneally,and helix spring was placed at the maxillary incisor.In group C,β-catenin agonist SB-415286 was injected locally into the premaxillary suture.Rats in groups A and B were given the same dose of DMSO,once a day in the premaxillary suture.The maxillary bone of rats was fixed with 10% neutral buffer formalin for 24 hours.After Micro-CT scan,the data Viewer reconstructed and analyzed the images and measured the width of the frontal suture,and observed the histomorphological changes of the frontal suture by hematoxylin-eosin staining,Masson staining.Immuno histochemistry was used to detect the expression of NF-κB p65,β-catenin and osteocalcin,bone morphogenetic protein-2 in rat premaxillary suture.Image-Pro Plus 6.0 biological image analysis system was used to analyze the expression of osteogenic factors,and the mean of integrated optical density value.Results1.The changes of body weight showed that the weight of group A increased steadily day by day,the average weight of groups B and C decreased on the 2nd and 3rd day,and the weight began to recover and increase after the 4th day.During the whole experiment,the average body weight of the two groups was lower than that of the A group(P < 0.05),but there was no significant difference between the B and C groups(P > 0.05).2.Micro-CT observation showed that at the beginning of the 4th day,there were obvious gaps in the premaxillary suture and a small finger protuberance in the middle of the premaxillary suture.On the 7th day,the width of premaxillary suture increased obviously,and the number and length of the digital protrusions increased significantly.Compared with group A,the width of premaxillary suture in group B and group C was significantly larger than that in group A(P<0.05).However,there was no significant difference in the width of premaxillary suture between B and C groups(P < 0.05).3.HE staining showed that in group A,the premaxillary suture was mainly composed of chondrocyte layer covered with palatal bone and fibrous tissue in the middle,and osteoblasts were sparsely arranged along the margin of bone tissue on both sides of the suture.On the 4th day in groups B and C,the premaxillary suture was broadened,bone-like formation was observed at the margin,and the bulky osteoblasts were arranged layer by layer on the new bone-like bone,and a large number of collagen fibers were proliferated between the premaxillary suture.After 7 days of distraction,the new bone formed a long and thin finger-shaped protuberance.The two sides of the finger-like bone were covered by the osteoblasts in the bone margin and the new bone,and direction of the collagen fibers in the premaxillary suture were horizontal and parallel to the horizontal stretch force.4.IHC showed that NF-κB p65 and β-catenin were rarely expressed in normal tissues,and in the whole experiment,NF-κB p65 and β-catenin were significantly expressed in the B and C groups,and the expression of p65 in group C was weaker than that in group B rats(P<0.05).In group B,the expression of β-catenin was more significant than that of group C(P<0.05).The mean of IOD values of BMP-2 and OCN were significantly higher in group B(P<0.05)than that in group A(P<0.05),and the mean of IOD values of OCN was higher in group C than that in group B(P<0.05).Conclusions1.The use of helix spring is effective in the premaxillary suture expansion of young adult rats and promote the formation of new bone in maxilla.2.Mechanical tension can activate the NF-κB and Wnt/β-catenin pathway in the premaxillary suture of young adult rats.There was bone remodeling activity in premaxillary suture expansion.3.The NF-κB p65 was down regulated by β-catenin agonist,and there was a negative regulatory effect between NF-κB and Wnt/β-catenin pathway.4.β-catenin agonist was used in the process of RME in rats,and the activity of NF-κB was inhibited.The increased expression of BMP-2 and OCN accelerates the process of bone deposition and calcification and bone remodeling.It will help to maintain the arch-expanding effect in the orthodontics.