| Objectives:To establish a TMJOA model of SD rat and evaluate the histological changes of condyle.The expressions of HIF-la and OPN in condylar cartilage were detected to investigate the roles of HIF-la and OPN in TMJOA and to provide experimental evidence for the pathogenesis of TMJOA.Methods:Eight-week-old male Sprague-Dawley rats were randomly divided into two groups:experimental group and control group.The model of TMJOA in SD rats was established by bonding an orthodontic wire on the right first maxillary molar teeth.Rats were sacrificed at 1,2,4,6,8 and 10 weeks post wire placement(5 rats in each group in experimental group and 2 rats in control group).The bilateral condyles were fixed,decalcified,dehydrated,and embedded in paraffin.Slides from experimental and control rats at each time point were stained with H-E and TRAP to evaluate the histopathological state of the condylar cartilage and subchondral bone.The Mankin's score of cartilage,morphometry and osteoclast of subchondral bone were statistically analyzed.Immunohistochemical staining was used to detect the expressions of HIF-1? and OPN at the various time points.Compare the expressions of HIF-la and OPN between the experimental group and the control group,and the experimental side and non-experimental side of experimental group.Results:1.Results of HE staining:Results of Mankin's score showed that the development of TMJOA as early as 2 weeks post-operative on the experimental side,and 4 weeks on the non-experimental side of experimental group.TMJOA-like lesions showed a diffuse increase in chondrocytes,mild disorder and unclear boundaries;irregular cartilage surface,fissures and cell-free areas in the proliferative layer.Subchondral bone morphological changes:Tb.Th,Tb.Sp,BV/TV,and Tb.N on the experimental side of the experimental group were higher than the control group at 1,2,4 and 10 weeks post-operative(P<0.05).Non-experimental side:BW/TV was lower than the control group(P<0.05)at 4 weeks;Tb.Sp was higher than the control group at 2weeks(P<0.05);Tb.Th,Tb.N were higher than the control group at 8 weeks(P<0.05).There were statistically significant difference between the experimental and non-experimental sides of the experimental group at 8weeks and 10weeks(P<0.05).2.Results of TRAP staining:Compared with the age matched control group,the number of osteoclasts were increased(P<0.05)at 1 week post-operative on the experimental side(P<0.05),and 2 weeks on the non-experimental side of experimental group(P<0.05),and reached a maximum at 8 weeks.The difference between experimental and non-experimental sides was statistically significant at 1 week(P<0.05).3.The results of immunohistochemistry showed that HIF-1? and OPN were mainly expressed in the nucleus and cytoplasm of hypertrophic cartilage and calcified cartilage.Compared with the control group,the positive expression of HIF-1? on the experimental side was enhanced(P<0.05)at 2weeks,decreased at 4w and 8w(P<0.05),and had no significant difference among 1,6 and 10 weeks(P>0.05).At non-experimental side,HIF-1? was higher than the control group at 2weeks(P<0.05),decreased at 6 weeks(P<0.05),and had no significant difference(P>0.05)at 1,4,8 and 10 weeks.The expression of HIF-la on experimental side was higher than the non-experimental side at 2 weeks(P<0.05)and lower than the non-experimental side(P<0.05)at 4 weeks.Compared with the control group,the positive expression of OPN on the experimental side increased significantly at 1w after modeling,decreased at 2w,increased at 4w and 6w,and decreased at 8w and 10w(P<0.05).The expression of OPN on non-experimental side of the experimental group was decreased at 2 weeks,increased at 4 weeks,and decreased 6 and 10 weeks(p<0.05).Compared with the non-experimental side,the expression of OPN on experimental side was higher than non-experimental side at 6weeks and lower than non-experimental side at 8weeks(P<0.05).Conclusions:1.In this experiment,we demonstrated an inexpensive and non-invasive TMJOA model of SD rat by bonding an orthodontic wire on the tooth surface.Pathological changes were observed in condylar cartilage and subchondral bone,including the disordered condylar chondrocytes,the cartilage fissure,condylar chondrocytes reduction and proliferative aggregation.The number of osteoclasts in the subchondral bone increases,and bone remodeling is active.2.HIF-la and ONP are mainly expressed in the nucleus and cytoplasm of the hypertrophic and calcified cartilage in TMJOA,HIF-1? and OPN were involved in the remodeling of condylar cartilage. |
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