The Role Of Schwann Cell TRPA1 In Orthodontic Pain

Background:Orthodontic pain is the inflammatory pain caused by orthodontic force,which often becomes one of the reasons for people to interrupt treatment.Orthodontic pain usually appears within a few hours after orthodontic exertion,peaks in 1 to 2 days,and completely resoles in about 7 days.Due to the long duration of the orthodontic treatment and the need for intermittent force,the pain usually remains with the patient throughout the treatment.At present,the mechanism of orthodontic pain is not clear.Existing treatment options for orthodontic pain include pharmacologic therapy and some non-pharmacologic therapies.There is no clear evidence of the effectiveness of non-pharmacological therapies for pain control,and although pharmacological therapies can relieve orthodontic pain,some drugs have been shown to inhibit the speed of orthodontic tooth movement.This requires us to control the orthodontic pain,but also need to consider a variety of complex conditions,including the influence factors of tooth movement.Therefore,it is very important to explore the mechanism of orthodontic pain.In the past,the focus of pain research was on neurons,but Schwann cells have become a new focus of chronic pain research in recent years.It has been proved that Schwann cells exist in the periodontal membrane,but the role of Schwann cells in orthodontic pain has not been understood.Transient receptor potential ankyrin 1(TRPA1),as a nonselective calcium channel,is also expressed in Schwann cells and is regulated by oxidative stress in Schwann cells rather than neurons.Facilitates chronic pain production and persistence.However,the role of TRPA1 receptor on Schwann cells during orthodontic tooth movement has not been reported.Purpose:This research studies the relationship between the expression changes of TRPA1 and Schwann cells during orthodontic treatment,and their relationship with orthodontic pain,and further studies the regulation of TRPA1,neurogenic mediators and inflammatory factors by Schwann cells under the action of mechanical forces in vitro.Method:1.Forty male Wistar rats aged 6-8 weeks were purchased and divided into groups to establish an experimental tooth movement model.The rats were randomly divided into two groups:experimental group(group A;n=20)and sham experimental group(group B;n=20),and group A and group B were equally allocated to 0d,1d,3d and 7d groups,5 rats in each group.All the treatment groups applied a force of 25g to simulate the movement of human orthodontic teeth,while the sham group did not activate the spring for control.The pain trend of rats before and after 1d,3d,5d and 7d were observed,and the changes of S-100β and TRPA1 positive signals in each group were analyzed by immunohistochemistry.The periodontal histological changes were observed,and the trend of pain was compared with the trend of S-100β and TRPA1 positive signals.2.After culturing Schwann cells in vitro and identifying Schwann cells by immunofluorescence,double immunofluorescence technology is used to locate the position of TRPA1 on Schwann cells.Apply Flexcell cell stress loading system to force Schwann cells in vitro to observe changes in Schwann cell state,and detect the genetic changes of TRPA1,CGRP,IL-6,and IL-8 by qPCR technology.Results:1.The experimental tooth movement model of rats was successfully established.Compared with control group,the mouth rubbing time and facial wiping times were prolonged on 1d and 3d after the appliance placement,and gradually returned to baseline after the peak on 1d.The first molar of rats moved medially and showed periodontal histological changes.The positive signal of Schwann cells and TRPA1 increased on 1d after orthodontic stress,and then decreased gradually to the same level as baseline on 7d.The positive signal distribution of Schwann cells and TRPA1 was consistent in the periodontal membrane.2.The primary Schwann cells were cultured to p4-p5 and identified as Schwann cells by S-100β.Dual immunofluorescence results showed that TRPA1 was present in the cell membrane around the nucleus of Schwann cells.Schwann cells were generally elongated and in good condition after tension was applied.Compared with the control group,the expression of TRPA1,CGRP,IL-6 and IL-8 in Schwann cells showed a decreasing trend with time under tension.Conclusion:1.Schwann cell TRPA1 is involved in orthodontic pain.2.The expression of TRPA1,neurogenic mediators and inflammatory factors decreased after Schwann cells were subjected to mechanical tension.