An Experimental Study On The Role Of Thrombospondin-4 In Rats With Myogenic Orofacial Pain

Objective:Myogenic facial pain is a muscle pain disorder in regional organization,which is the most common cause of persistent regional pain.The exact pathogenesis is still unknown,as a result,there is no clear and effective therapeutic method.Thrombospondin-4(TSP-4)is a member of thrombospondins.Current studies have shown that TSP-4 is an extracellular calcium-binding protein which can regulate cell migration,proliferation,adhesion,tissue remodeling,angiogenesis,tumor growth,nerve development,and pain signaling.Recent studies show that TSP-4 was involved in the development and progression of neuropathic pain.The expression of TSP-4 was upregulated by nerve injury in neuropathic pain.The pain was reversed when TSP-4antibodies or antisense oligodeoxynucleotides were injected to inhibit its function.However,the role of TSP-4 in myogenic facial pain is still unknown.In this study,the model of myogenic orofacial pain was established by the ligation of anterior superficial part of masseter muscle in rats.The expression level of TSP-4 mRNA in trigeminal spinal subnucleus caudalis and C1-C2 spinal cervical dorsal horn(VC/C2)were measured in myogenic orofacial pain.TSP-4 antibody was injected into masseter muscle of the ligated side to block the function of TSP-4,and the mechanical threshold was assessed.The aim of the study is to explore the role of TSP-4 in rats with myogenic orofacial pain and provide information for the clinical treatment of pain.Method:Twleve SD rats were divided into ligation group and sham group randomly.The anterior superficial part of masseter muscle(TASM)was ligated in the ligation group.While the TASM was not ligated in the sham group.The mechanical threshold was assessed before surgery and 3,7,10,14 days after surgery by von Frey filaments.The expression level of TSP-4 mRNA in V_C/C2 were measured by qRT-PCR 14 days after surgery.TSP-4 antibody was injected into masseter muscle of the ligated side to block the function of TSP-4.The mechanical threshold was assessed before injection and 2,4,6,12 hours after injection by Von Frey filaments.Results:(1)In the ligation group,compared with the pre-operation,the mechanical threshold of rats was significantly decreased 3,7,10 and 14 days after operation.(P<0.05).In the sham group,compared with the pre-operation,the mechanical threshold has no significant change(P>0.05).Compared with sham group,the mechanical threshold was significantly decreased and maintained throughout 14 days observation in ligation group(P<0.05).(2)Compared with sham group,the expression level of TSP-4 mRNA in VC/C2 were significantly upregulated 14 days after surgery in the ligation group(P<0.05).(3)When TSP-4 antibody was injected into masseter muscle of the ligated side to block the function of TSP-4,the mechanical threshold of rats was significantly increased at 4 hours and 6 hours(P<0.05).Conclusion:The expression level of TSP-4 mRNA was significantly increased in myogenic orofacial pain of rats,and the function of TSP-4 plays an important role in myogenic orofacial pain of rats.TSP-4 is involved in the pathogenesis of myogenic orofacial pain of rats which would provide information for the clinical treatment of pain.