| Objective: Stromal cell-derived factor-1 is a newly discovered member of the α chemokine family.In recent years,it has been found that the signaling system composed of SDF-1 and its receptor CXCR4 plays an important role in osteogenic differentiation,remodeling,mineralization and bone marrow osteogenesis of fracture healing.Studies have shown that the up-regulated factor HIF-1 of SDF-1 can accelerate fracture healing after traumatic brain injury.In this study,we established models of tibial fracture after traumatic craniocerebral injury or sciatic nerve cutting off to investigate the expression changes and mechanism of SDF-1 in the process of fracture healing after denervation.Methods: The 216 rats were randomly divided into group A(only tibial fracture),group B(traumatic craniocerebral injury combined with tibial fracture)and group C(sciatic nerve transection combined with tibial fracture)and each group was 72 rats.The rat models of tibia fracture,traumatic brain injury(TBI)combined with tibial fractures and sciatic nerve transection combined with tibial fracture were established.12 rats were respectively killed on the 3rd,5th,7th,14 th,21st and 28 th day after operation in every groups.Six of them removed the full-length right tibia,which used for HE staining and immunohistochemical staining after weigh.The remaining 6 rats were used to examine the expression of SDF-1 in callus by RT-PCR.Results: The results of wet weight of the full-length tibia showed that group B was significantly different from that of group A at all time points after operation(P <0.05).The wet weight of the full-length tibia in group B compared with group C,the difference was not statistically significant(P> 0.05).The wet weight of tibia in group C at each time point after operation was significantly different from that of group A(P <0.05).A,B,C three groups of tibia wet weight were significantly higher 7 days after operation and achieve the maximum value.Immunohistochemistry showed that the number of positive staining chondrocytes in group B and group C at 5d,7d and 14d after operation was significantly higher than that in group A(P <0.01).There was no significant difference in the number of chondrocytes stained positive in group B and C compared with group A at 21 and 28 days after operation(P> 0.05).The number of chondrocytes stained positive at 5 days after operation in group C was significantly higher than that in group B,the difference was statistically significant(P <0.01).There was no significant difference in the number of chondrocytes stained positive in group B and group C after 7d,14 d,21d,and 28d(P>0.05).The number of positive staining osteoblasts in group A at 14 d and 21 d after operation were significantly higher than those in group B and C(P <0.01).There was no significant difference in the number of osteoblasts stained positive in group A at 28 days after operation compared with those in groups B and C(P> 0.05).The number of osteoblasts stained positive in group B and group C on the 14 day after operation was significantly higher in group C than in group B,the difference was statistically significant(P <0.01).There was no significant difference in the number of osteoblasts positively stained between group B and group C on days 21 and 28 after surgery(P>0.05).RT-PCR results showed that SDF-1 m RNA of group B and group C was expressed on the 3rd day after operation and gradually increased.The peak was on the 7th day after operation and still remained partially on the 28 th day.The expression of SDF-1 m RNA in group A began to be expressed on the 5th day after the operation,reached the peak on the 14 th day,and still remained partially on the 28 th day.The expression of SDF-1 m RNA in group B and group C at 3d,5d and 7d after operation was significantly higher than that in group A(P <0.01).The expressions of SDF-1 m RNA in group A and group B were significantly higher than those in group B and C on the 14 th and 21 st day after operation(P <0.01).The expression of SDF-1 m RNA in group B and C at 28 days after operation was slightly higher than that in group A,with no statistically significant difference(P>0.05).The expression of SDF-1 m RNA in group C was significantly higher than that in group B at 5 days after operation(P <0.01).The expression of SDF-1 m RNA in group B was not significantly different from that in group C at 3d,7d,14 d,21d and 28d(P> 0.05).Conclusion:SDF-1 is highly expressed in the early phase of denervation fracture healing and plays an important role in the accelerated healing process of denervation fracture healing.Moreover,it may play a role in the early stage of fracture healing by recruiting mesenchymal stem cells,promoting osteogenic differentiation,and regulating neovascularization Etc. |
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