The Research Of DLK2 On The Cartilage Development And Temporomandibular Joint Osteoarthritis

Objective:Temporomandibular joint osteoarthritis is a common temporomandibular disorder(TMD)characterized by progressive cartilage degeneration,subchondral bone sclerosis and synovial inflammation.Based on preliminary study,DLK2(delta drosophila homolog-like 2 or delta like 2 homologue)was considered a possible factor that involved in TMJOA.Therefore,to investigate the role of DLK2 in cartilage development and TMJOA,we examed the expression of DLK2 during the cartilage development and in the model of TMJOA by immunohistochemistry;and studied the effect of DLK2 overexpression on the proliferation and differentiation of ATDC5 cells.Methods:1.To compare the expression of DLK1 and DLK2 in knee catilage during the deveopment of cembryo knee cartilage by immunohistochemistry.2.To construct ATDC5-DLK2 over-expression cell lines,and to study the effect of DLK2 on proliferation and differentiation of ATDC5 cells.3.To construct TMJOA animal model by injecting VEGF into capsule of temporomandibular articular in SD rats.4.To analyze the expesson of DLK2 in modle of TMJOA;then to investigate the effect of DLK2 on MMPs and ADAMTSs by overexpresseing DLK2 in ATDC5cells;Results:1.The pattern expression of DLK2 during in the development of embryonic knee cartilage and enamel is inconsistent with DLK1 examed by immune histochemistry: During embryonic period,DLK2 was significantly expressed both in immature and mature chongdrocyte cells,and the stain of DLK2 in articular cartilage surface was gradually decreased,but was still strong in deep;However the stain of DLK1 was just in immature chondrocytes,and dramatically decreased immediately after birth which narrowed in the rest zone of cartilage;2.DLK2 decreased during the differentiation of ATDC5 cells;and DLK2 ovexpression enhanced the proliferation of ATDC5 cells but suppressed the expression of chondrogenic marker genes(col2a1,acan,col10a1)during the differentiation;3.HE staining showed that the thickness of the condylar cartilage layer of VEGF group were significantly much narrower than the control group and the saline group;toluidine blue and safranin O staining showed that the cartilage matrix of VEGF group decreased from the second week,chondroctye clustering and cartilage vacuolar also were not to disappear until the last condylar cartilage disappeared;the modified Mankin score of VEGF group score was significantly higher than the control group and the saline group from the second week;micro-CT showed that the lesions of condyle subchondral bone increased with the time;immunohistory showed that the expression of MMP9 and MMP13 in VEGF group was much more than the control group and the saline group at week 1and2;the apoptosis cells in VEGF group was also more than the control group and the saline group at week 1and 2.4.DLK2 increased during the development of TMJOA animal model.And dlk2 ovexpression enhanced the expression of MMP13 and ADAMTS5,while it had no effect on MMP9 and ADAMTS4.Conclusion:DLK2 may be an important factor of cartilage development and TMJOA,and it could be a potential therapeutic target of TMJOA.