| Objective: To investigate the effect of parathyroid hormone(PTH)on the healing of condylar cartilage in rabbits with mandibular condylar free fracture and cartilage injury.Methods: An experimental model of free reduction and internal of condylar fracture was established in 48 New Zealand rabbits,which were randomly divided into experimental group and control group.The experimental group received with intermittent subcutaneous injectons of PTH 20mg/kg,and the control group was injected with 1ml of normal saline.The animals were sacrificed at 1 week,2 weeks,3weeks,and 4 weeks after surgery.The mandibular condyle specimens of the surgical side were taken for gross morphological study,Hematoxylin and eosin staining(HE)staining and saffron O-solid green staining were used to detect changes in cartilage structure in the fracture area of condyle cartilage and degradation of matrix around the fracture.Immunohistochemistry(IHC)was used to detect the expression of Sox9(SRY-related high mobility group-box gene-9)and matrix metallopeptidase 13(MMP-13)in the new cartilage tissue of condylar fracture.The Sox9,MMP-13,Col2al(Collagen type Ⅱ,Col2al)and ColⅩ(Collagen type X,ColⅩ)m RNA expression were detected by PCR.Results: The results of saffron o-solid green staining and HE staining indicated that the degradation of cartilage fracture area matrix was more obvious in the control group than in the experimental group.the inflammatory cells in the fracture area below the cartilage were more obvious than in the experimental group.the number of chondrocytes and the deposition of cartilage matrix in the cartilage fracture area were less than in the experimental group and fibrous tissue filling was observed in the cartilage fracture area in the control group.In immunohistochemistry,the staining intensity of Sox9 factor in the experimental group at each period was stronger than that in the control group,suggesting that the expression of Sox9 in the experimental group was stronger than that in the controlgroup and the difference was statistically significant at 1 week,2 weeks and 3 weeks after surgery(P<0.05),The staining intensity of MMP-13 in the experimental group was lower than that in the control group at each period,suggesting that the expression level of MMP-13 in the experimental group was lower than that in the control group.and the difference between the two groups was statistically significant at 1,2 and 3weeks after surgery.The expression level of Sox9 relative m RNA expression in the experimental group was significantly higher than that in the control group at each period and the difference was statistically significant at 1,2 and 3 weeks after surgery(P<0.05).The expression of MMP-13 relative m RNA expression in the experimental group was lower than that in the control group and the difference was statistically significant at 1,2 and 3 weeks after surgery(p<0.05).The expression level of Col2 al relative m RNA expression in the experimental group was higher than that in the control group at each period and the expression difference between the two groups was statistically significant at 2,3 and 4 weeks after the operation(p<0.05).The expression level of ColⅩ relative m RNA expression in the experimental group was lower than that in the control group at each period,and the expression difference between the two groups was statistically significant at 2,3 and 4 weeks after the operation(p<0.05).At 4 weeks after surgery,there was no significant difference in the staining intensity and relative m RNA expression of MMP-13 and Sox9 between the experimental group and the control group.1 week after the operation,there was no significant difference in Col2 al and ColⅩ staining intensity and relative m RNA expression between the control group and the experimental group.Conclusions:Intermittent subcutaneous injection of PTH can up regulate the expression of Sox9 and Col2 al,inhibit the expression of MMP-13 and ColⅩ and accelerate the repair of cartilage damage. |
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