Effect Of Experimentally Created Disordered Occlusion On The Expression Of IL-1β, IL-6and TNF-α In Condylar Cartilage Of Rats

Our previous studies showed that experimentally created disorderedocclusion(ECDO) induces degradation in the rat condylar cartilage. Cytokinesregulate the functions of chondrocytes through various mechanism. The aim ofthis study is to investigate the effect of the experimentally created disorderedocclusion (ECDO) on the expression of IL-1β, IL-6and TNF-α in mandibularcondylar cartilage of Sprague Dawley (SD) rats.Thirty-two8-week old female SD rats were randomly and equally dividedinto2ECDO groups and2control groups(n=8). The animals were fed in thesame environment. In experiment groups, the disordered occlusion was createdby moving the first and third molars0.8mm away. No treatment was applied tocontrol group. HE and immunohistochemical staining were performed on themandibular condylars at the end of the8th or12th week. Gene expression was analyzed by real-time PCR.The main results are as follows：1. The condylar cartilage in the control groups was typically organized intothe fibrous layer, proliferative layer, hypertrophic and calcified cartilage layer. InECDO groups, degenerative changes, such as a disarrangement of cellulardispostion， condensed nuclei, coagulative necrosis, decreased number ofchondrocytes，the emergence of cell free areas，can be found in4from8condyles in8-week ECDO subgroup and6from8condyles in12-week ECDOsubgroup. The degenerative changes were severer in12-week ECDO subgroupthan those in8-week ECDO subgroup.2. The results of immunohistochemical staining were as follows: IL-1β, IL-6and TNF-α were mainly expressed in hypertrophic layer of condylar cartilage,with obvious signals in the cytoplasm of chondrocytes. In the regions withsevere cell-free changes in ECDO groups, the immunopositive expressions ofthese three inflammatory factors were absent.3. The results of PCR：the levels of IL-1β, IL-6and TNF-α were notsignificantly different among the control groups (P>0.05). The expression ofIL-1β was not significantly different in ECDO subgroups,while the expressionof IL-6in8-week ECDO subgroup was higher than8-week control subgroup(P=0.009), and the expression of TNF-α in8-week ECDO subgroup was higherthan8-week control subgroup (P=0.001) and than12-week ECDO subgroup(P=0.004).Conclusions:1．ECDO induces degradation in the rat condylar cartilage.2. At the early period in present study, IL-6and TNF-α, but not IL-1β,exhibited important roles in the degenerative remodeling procedure in rat condylar cartilage induced by ECDO.