Effect Of Unilateral Chewing On The Expression Of DMP1 In SD Rat Condylar Cartilage

Objective:To investigate the effect of unilateral chewing on the expression of DMP1 in SD rat condylar cartilage.Methods:40 healthy male 8-week-old SD rats were randomly divided into experimental group and control group with equal number distribution.In experimental group,we built the model of unilateral chewing through extracting the right side of maxillary molars,and then SD rats were sacrificed at 2,4,6,8 weeks after operation.The mandibular condyles of SD rats were taken out for conventional fixation,decalcification,dehydration,embedding,paraffin section and staining.HE staining was made for the observation of histological changes of condylar cartilage and subchondral bone,the measurement of condylar cartilage thickness and the morphometric analysis of subchondral bone.Immunohistochemical method was used to detect the expression of DMP1 in condylar cartilage of SD rats at different time points.Image analysis was performed using Image Pro Plus 6.0 image analysis system.All datas were analyzed by SPSS23.0 statistical software.Results:1.HE staining showed that condylar cartilage and subchondral bone had pathological changes,the thickness of condylar cartilage was decreased and subchondral bone was disordered in the experimental group.The measurement of condylar cartilage thickness showed:the thickness of cartilage in the extraction side and the non-extraction side of the experimental group was lower than that in the control group at 4w,6w,8w after operation(P<0.05),and there was no significant difference between the extraction side and the non-extraction side(P>0.05).The morphometric analysis of subchondral bone showed:BV/TV of the extraction side and the non-extraction side were lower than the control group at 2w,4w,6w after operation(P<0.05);Tb.Th and Tb.N of the extraction side and the non-extraction side were lower than the control group at 2w after operation(P<0.05);Tb.Sp of the extraction side and the non-extraction side was higher than the control group at 2w,4w after operation(P<0.05).2.Immunohistochemical results showed:the expression of DMP1 in the condylar cartilage was positive in the experimental group and the control group,expressed in the nucleus and cytoplasm of the chondroblastic and hypertrophic layers.The expression of DMP1 in the extraction side and non-extraction side were higher than that in the control group at 2w,4w,6w and 8w after operation(P<0.05).There was no statistical difference on the expression of DMP1 between the extraction side and the non-extraction side(P>0.05).There were statistical differences on the DMP1 expression of the extraction side between 2w and 4w,4w and 8w after operation(P<0.05);there were statistical differences on the DMP1 expression of the non-extraction side between 2w and 4w,4w and 6w after operation(P<0.05).Conclusions:1.The unilateral chewing caused by extracting tooth could lead to pathological changes of the mandibular condylar cartilage and subchondral bone in the experimental group.The thickness of the condylar cartilage was thinner and the number,morphology,arrangement of subchondral bone trabeculae were abnormal.There was no significant difference in the pathological changes of the mandibular condylar cartilage and the subchondral bone between the extraction side and the non-extraction side.2.DMP1 was involved in the growth and development of condylar cartilage,mainly expressed in the nucleus and cytoplasm of the chondroblastic and hypertrophic layers.The positive expression of DMP1 in the condylar cartilage was higher than that in the control group,indicating that DMP1 was involved in the reconstruction of condylar cartilage caused by unilateral chewing.