| Objective:To establish the animal model of different age SD rats,and then observe the development of temporomandibular joint condylar and the expression of DMPl in condylar cartilage.To explore the development of TMJ with effect of masticatory force changes in different growth stage.Methods:Experiment 1:Thirty SD rats were selected and 6 rats in each group:(0),3,5,6,8 weeks old male SD rats.The rats were sacrificed by deep anesthesia.The histological changes of condylar cartilage were observed.The expression of DMP1 in condylar cartilage was detected by immunohistochemical method.Experiment 2:Thirty six SD rats were randomly divided into two groups:experimental group(soft diet)and control group(normal diet).The rats were sacrificed at 2,4 and 6 weeks after modeling.The expression of DMP1 in condylar cartilage was also detected by immunohistochemical staining.Image analysis was performed using Image Pro Plus 6.0 image analysis system.SPSS 23.0 software was using in analysis all of the data.Results:(1)Experiment 1:The thickness of the cartilage was decreased at 0-8 weeks,and it was characterized by extreme reduction at 3-8 weeks(P<0.05),and the proliferation layer showed a increase tendency(P<0.05),while Tb.N showed a decreasing trend with the increase of age(P<0.05),Bb/TV and Tb.Th showed a increasing tendency(P<0.05),Tb.Sp:no significant difference between any two groups(P>0.05);DMP1:mainly expressed in the condylar cartilage in the mature layer and hypertrophy layer.In 0-8 weeks,the expression of DMP1 in the mature layer showed a decreasing trendency(P<0.05).(2)Experiment 2:Cartilage thickness:At the age of 8w,lOw and 12w,the condylar cartilage thickness of experimental group are more thinner than control group(P<0.05);Subchondral bone:Compared with control group at 8w,10w and 12w,experimental group’s BV/TV and Tb.Th were significantly lower than that of the control group(P<0.05).But Tb.N showed an increasing trendency(P<0.05).There were no significant difference about Tb.Sp between any two groups(P>0.05).At 8w and 10w,the expression of DMP1 in experimental group were lower than that in control group(P<0.05).But at 12w,the expression of DMP1 in experimental group was little lower than that in control group(P>0.05).Conclusions:1,From the age of 3w(after weaning),there have a great accelerating growth and development in condylar,indicating that chewing force play an important role in condylar’s developing.2,Soft diet feeding does not lead to weight loss in rats,but the reduction of chewing force can lead to condylar’s degeneration.3,DMP1 mainly expressed in the cartilage of mature layer and hypertrophy layer,and it plays an important role in condylar’s developing.It suggested that DMP1 may be involved in biomechanical signaling pathways. |
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