Research On Novel Methods And Mechanism Of Accelerating Bone Regeneration During Distraction Osteogenesis

Purpose: With high disability rate,large bone defects still lack of satisfactory treatment.Distraction osteogenesis(DO)has been one of the most dramatic reconstructive techniques for managing bone defect and nonunion since it was applied in clinic.However,the procedure involves long period for bone consolidation in large defect,which increases the rate of complications and brings heavy physical and psychological burdens in patients.Therefore,novel methods such as mechanical stimulation,growth factors,stem cells,proteins,biomaterials,microRNA,and drugs were developed in our study to accelerate bone regeneration during distraction osteogenesis,and the related mechanisms were tried to clarified.Methods: The procedure of bone formation in distraction zone was intervened locally by different approaches including accordion technique,staphylococcal enterotoxin C2(SEC2),human fetal mesenchymal stem cells(hFMSCs)secretome,porcine brain extract(PBE),polycaprolactone/hydroxyapatite(PCL/HA)composite microspheres,overexpression of miR-503 in rBMSCs,and SDF-1/Cxcr4 signaling antagonist AMD3100.In vitro,rBMSCs were treated and the effect on osteogenic differentiation was determined by osteogenic staining and related genes detection.In vivo,a rat tibial distraction osteogenesis model was performed.New bone quality and related mechanism were subject to X-rays,micro-computed tomography(μCT),mechanical testing examination,western bolt analysis,histology,and immunohistochemistry examinations.Results: In vitro,the ability of osteogenic differentiation was significantly enhanced after administration of SEC2,hMSCSs secretome,PBE,PCL/HA,and miR-503,while it was inhibited after treated by AMD3100.In vivo,all approaches except AMD3100 could remarkably accelerate new bone formation.For the mechanism,accordion technique was effective in promoting bone consolidation via activation of HIF-1α/VEGF during DO;SEC2 can increase the level of IL-6 and IL-1,which may contribute to the enhancement of bone consolidation;hFMSCs secretome could accelerate callus formation through the possibly elevated levels of BMP2 and VEGF;the multiple kinds of growth factors in PBE should be responsible for increased bone regeneration;the PCL/HA microspheres could not only improve the mechanical properties of the regenerates but also promote the angiogenesis because of the degradation of HA;and the miR-503 could suppress Smurf1 expression to promote bone formation.Also,from the inhibited effect of AMD3100,the important role of SDF-1/Cxcr4 in bone consolidation during distraction osteogenesis was demonstrated.Conclusions: In our research,we demonstrated that distraction osteogenesis in rat tibia is an effective model to study bone regeneration.Different novel approaches including mechanical stimulation,SEC2,hFMSCs secretome,PBE,PCL/HA microsphere,and miR-503 could accelerate bone consolidation.Furthermore,related signaling pathways were demonstrated during distraction osteogenesis.Our findings may contribute to the rapid bone regeneration in patients with large bone defects in clinic.