Mechanism Investigation Of Posttraumatic Heterotopic Ossification By SDF-1/CXCR4 Mediated Osteogenic Differentiation Of Bone Marrow Mesenchymal Stem Cells

Background:Posttraumatic Heterotopic Ossification(PTHO)refers to the formation of abnormal bone tissues in places other than normal bone after various traumas.PTHO is common in hip joint,elbow joint and other parts of human body,and can also appear in the spine.Heterotopic ossification around joints after trauma can cause pain,limb dysfunction,and joint rigidity in severe cases.Heterotopic ossification of spine can also cause spinal stenosis and nerve compression symptoms.At present,the clinical prevention and treatment methods include drug therapy,radiotherapy,etc.,but they have not achieved satisfactory curative effect.There are many studies on posttraumatic heterotopic ossification,but none of them can clearly explain its mechanism.Therefore,it is of great significance to further study and clarify the pathogenesis of posttraumatic heterotopic ossification,so as to explore new methods for prevention and treatment of heterotopic ossification.Objective:Stromal cell-derived factor-1(SDF-1)belongs to the CXC subfamily of chemokines,also named CXCL12,which activates downstream signals and regulates many biological processes by binding to its receptor CXCR4 and CXCR7.Studies have shown that the activation of SDF-1/CXCR4 signal axis can promote the repair of bone defects and accelerate fracture healing when fracture is complicated with craniocerebral injury.In view of the similarities between the occurrence and development of heterotopic ossification and fracture healing and bone defect repair,this study intends to explore the mechanism of SDF-1/CXCR4 signal axis mediating bone marrow mesenchymal stem cell(BMSC)osteogenic differentiation to promote the formation of heterotopic ossification after trauma.Methods:(1)Expression of SDF-1 and its receptor in mature heterotopic ossified human tissues formed after trauma was detected by immunohistochemistry.(2)The animal model of posttraumatic ectopic ossification was established.In order to investigate the pathogenesis of posttraumatic heterotopic ossification,the degree of heterotopic ossification was detected by X-ray,and the expression of SDF-1/CXCR4 signaling pathway and possible downstream signals JAK2 and STAT3 in the early stage of posttraumatic heterotopic ossification was detected by immunohistochemistry,RT-PCR and Western blot.(3)The effect of SDF-1 and its receptor CXCR4 on osteogenic differentiation of BMSC and its key signal mechanism were investigated in vitro.Results:(1)The expression of SDF-1 and its receptor in heterotopic ossified human tissues was higher than that in non-heterotopic ossified human tissues.(2)The results of animal experiment turned out that the expression of SDF-1/CXCR4,JAK2 and STAT3 was higher in rats with traumatic heterotopic ossification.(3)In vitro experiments confirmed that SDF-1 promoted the activation of JAK2/STAT3 in BMSCs,SDF-1/CXCR4 promoted the osteogenic differentiation of BMSCs,and SDF-1/CXCR4 activated JAK2/STAT3 and regulated BMSCs osteogenic differentiation.Conclusion:In this study,the expression of SDF-1 and its receptor in human posttraumatic heterotopic ossification tissues was detected,and an animal model was established to explore the SDF-1/CXCR4 signaling pathway and possible downstream signal expression of JAK2 and STAT3 during posttraumatic heterotopic ossification.Combined with in vitro experiments,it was demonstrated that SDF1/CXCR4 activated JAK2/STAT3 to regulate BMSCs osteogenic differentiation,and found that SDF-1/CXCR4 axis mediated BMSCs osteogenic differentiation plays an important role in the formation of posttraumatic heterotopic ossification.These results suggest that SDF-1/CXCR4 axis may be a new therapeutic target for posttraumatic heterotopic ossification.