The Effect Of Wnt/β-catenin Signaling Pathway On The Orthodontically Induced Root Resorption Repair Process: A Preliminary Study In Rats

With the development of economy and living standards,more and more people begin to seek for orthodontic treatment.The process of orthodontic treatment is mainly to make the teeth move to its ideal location using various treatment devices.In this process,there has not only the reconstruction of alveolar bone,but also a rebuiltment of cementum.Abnormal cementum reconstruction will lead to some common complication,i.e orthodontically induced root resorption(OIRR).OIRR belongs to inflammatory resorption,light matter can repair itself,however,severe may lead to root-shorten,or even root-loosing,which ultimately affect the long-term stability of orthodontic treatment.Therefore,scholars have been exploring and seeking the relevant mechanisms and treatment methods of OIRR.Previous studies have shown that Wnt/β-catenin signaling pathway plays an important role in growth development of various body tissues.In the process of tooth development,Wnt/β-catenin signaling pathway is involved in different stages of tooth development through the mediation of a variety of gene transcription,but it has not yet been found that if it plays a role in the repair of OIRR.Therefore,Our study establish a rat model of repair of OIRR,using Micro-CT scanning and combining with H&E staining and immunohistochemical techniques to preliminary explore the effect of Wnt/β-catenin signaling pathway on the repair process of OIRR,to find a feasible method to accelerate the repair process of root resorption.Part 1: Using Micro-CT scanning to detect the effect of activation/inhibition of Wnt/β-catenin signaling pathway on the root resorption repair process.Objective: Using Micro-CT to observe the influence of activation/inhibition of Wnt/β-catenin signaling on the changes of alveolar bone microstructure and the root resorption volume during repair process of OIRR.Methods: A total of sisty adult male SD rats,with the left maxillary first molar as the experimental side,were selected.A NiTi spring forced 100 g was ligated between the left upper first molar and ipsilateral central incisor to pull the molar moving mesial for 14 days,and then remove.The rats were randomly divided into three groups: the LICL group,the DKK1 group and the control group,20 rats in each group.Since the demolition of device,the LICL group was injected LICL solution at the flexure of mucosa of left maxillary first molar with a dosage of 0.2 ml/kg,once every twice days;the DKK1 group was inject DKK1 protein with a dosage of 0.2 ug/kg,once every twice days,the control group without any injection.Micro-CT was used on the day 0 and day 14 after the device removal,to scan the left first and second upper molars and their surrounding tissue,and then account the difference of the two scanning results on resorption volume and structural parameters of trabecular bone.The results were analyzed by SPSS 19.0 software.Results: There were no significant difference about the root resorption craters volume and tructural parameters of trabecular bone in three groups on day 0(P>0.05).However,on day 14,the volume of root repair in the LICL group and control group were significantly less than the day 0 and the DKK1 group displayed significantly greater than the day 0;the repair volume in LICL group was greater than that of control group(P<0.05);the LICL group and control group had an increase in BV/TV,Tb.N and Tb.Th and a decrease in SMI,Tb.Sp,while in the DKK1 group,the BV/TV,Tb.N and Tb.Th decreased,SMI and Tb.Sp increased.The changes of SMI,Tb.N and Tb.Th in the three groups were statistically significant(P<0.05).There were no significant difference in the changes in BV/TV and Tb.Sp between the control group and the LICL group(P>0.05),the changes of BV/TV and Tb.Sp in the control group and the DKK1 group were significant(P<0.05).Conclusion: The Wnt/β-catenin signaling pathway is involved in the orthodontically induced root resorption repair process in rats,and the activation of Wnt/β-catenin signaling pathway can enhance the effect of root repair.Part 2: The effect of activation/inhibition of Wnt/β-catenin signaling pathway on the expression of Axin2,β-catenin,BMP-2,BSP and CAP in the root resorption repair process.Objective: To assess the effects of activation/inhibition of Wnt/β-catenin signaling pathway on the expression of Axin2,β-catenin,BMP-2,BSP and CAP in the root resorption repair process by using H&E staining and immunohistochemistry technology.Methods: The model was same to the Part 1.On days 0.3.7.10.14 after orthodontical device removal,the rats were killed 4 rats once.H&E staining was used to observe the morphological changes of periodontal tissue,and the expression of of Axin2,β-catenin,BMP-2,BSP and CAP in periodontal tissue was detected by immunohistochemical method.Results:1.H&E staining: With the repair time lasting,the LICL group of root resorption lacunae became smaller,in the the days 7~14,the root resorption lacunae significantly reduced,on day 14,the periodontal fibers were relatively regular in arrangement.In the DKK1 group,during the days 0~10,the root resoption futher occurs,during 10~14 days after repair,the changes the resorption tends to stop;the control group in the repair of 0~3 days,the root resoption futher occurs,3~14 days after repair,the repair started slowly,on day 14,the root still had obvious resorption craters.2 Immunohistochemistry: With the time increasing of repair,in the LICL group,the expression of Axin2,β-catenin,BMP-2,BSP and CAP were gradually increased,the expression of β-catenin,BMP-2 and BSP reached the peak;the expression of Axin2,β-catenin,BMP-2,BSP and CAP in the group DKK1 was gradually decreased and reached the lowest on day 10.The positive expression of Axin2,β-catenin,BMP-2,BSP and CAP in three groups were not statistically significant on the day 0 of repair(P>0.05),on day 3,the expression of BMP-2,BSP and CAP in three groups,the expression of β-catenin in the LICL group and the DKK1 group were statistically significant(P<0.05);on day 7,the expression of Axin2、β-catenin、BMP-2、BSP and CAP in LICL group and DKK1 group and the expression of BMP-2、BSP and CAP in DKK1 group and control group were statistically significant(P<0.05);on days 10 and 14,the expression of Axin2、β-catenin、BMP-2、BSP and CAP in three groups were statistically significant(P<0.05).Conclusion: The Wnt/β-catenin signaling pathway could regulate the expression of Axin2,β-catenin,BMP-2,BSP and CAP in the process of root resorption repair to some extent.