| The rapid development of implant technology has changed the traditional restoration methods and has become an important means to restore dentition defect, edentulous jaw. The bone quality and quantity around the implant is the vital factor of the successful cultivation, the key is to get an ideal osseointegration. The central part is the bone marrow mesenchymal stem cells (BMSCs) migrate to implant-bone interface and proliferation, differentiation and osteogenesis.Currently, the common methods to improve the function of BMSCs in implant restoration include implant surface modification, physical stimulation, chemical factors, especially biological factors and drugs inject, implant surface modification and biochemical factors has been studied widely. Bone is a natural electrets material; the electric field can promote fracture healing. Current research has shown that the DCEF can promote the bone healing after implantation in alveolar dog and rabbit tibia. DCEF has the well ability of osteogenesis, but how they affect the function of BMSCs and the mechanism is unclear. Therefore, the purpose of this study is to investigate the effects of DCEF on promoting migration and osteogenesis of bone marrow mesenchymal stem cells around dental implant through cytological studies and animal experiments, in order to provide a new method for improving clinical implant restoration effect.The first part:The isolation, cultivation and identification of GFP-BMSCsObjective:To complete the cultivation and identification in vitro of rat BMSCs GFP cells and uses it after three generations.Results:The cultured BMSCs proliferated in vitro showed morphological characteristics of stem cell properties, uniform shape, strong capacity of proliferation,which can adipogenic and osteogenic differentiation; Flow cytometry to identify their cell surface markers show positive characteristic of CD29, CD90, CD71, negative characteristic of CD45, CD86 and CD80.Conclusion:The cultured BMSCs rat cells are morphology and composition homogeneous, purified complete and have the ability of multipotential proliferation, its cell phenotype is in line with the characteristics of stem cells.The second part:The screening for the best time of DCEF in promoting BMSCs migration, osteogenesis and proliferationObjective:To screen the optimal time of DCEF in promoting BMSCs migration and the impacts of DCEF on cell osteogenesis and cell proliferation.Results:Under 200mv/mm intensity, the optimal action time of electric field in promoting cell migration is 4 hours. During the 4 hours, obtain a maximum of ALP staining bone nodule, so exert DCEF load on the BMSCs can promote its proliferation.Conclusion:Under 200mv/mm DCEF strength,4 hours action time can promote the biological properties of migration, proliferation and osteogenesis to BMSCs.The third part:The effects DCEF on the migration mechanism of BMSCs and osteogenic differentiationObjective:To study the mechanisms of DCEF on the migration of BMSCs, and the effects of DCEF on BMSCs osteogenic differentiation in osteogenic related genes and protein levels.Results:Under 200mv/mm, four hours of the role of DCEF, the migration of BMSCs is concerned with SDF-1/CXCR4 axis. After the intervention of DCEF, the gene expression level of OCN, BSP and the protein expression level of ALP, RUNX2 were significantly increased.Conclusion:In terms of the gene and protein level, DCEF can promote BMSCs osteogenic differentiation.The forth part:The effects of DCEF on synosteosis between titanium implant and tibia in SD ratsObjective:To investigate the effects of DCEF on BMSCs migration during synosteosis between titanium implant and tibia in rats through animal studies.Results:Applied a DCEF, the quantity of GFP-BMSCs in rats migrate to the surrounding implant is more than the control group. After 4 weeks of implant placement, in the experimental group which exert DCEF of 200mv/mm,4 hours, the bone implant contact rate, which significantly higher than the control group that electric field is not loaded. While trabecular gap significantly lower compared with the control group (P< 0.05), that is a higher bone density. The above parameter indicates the bone quantity of exerted electric field group was significantly higher than the electric field is not loaded group; the average unscrew torque value in the first four weeks and eight weeks in the exerted electric field group were significantly higher than those the electric field is not loaded group. The implant osseointegration rate on rat tibia in the first four weeks in the exerted electric field group were significantly higher than those the electric field is not loaded group, which consistent with the results of implant osseointegration rate, exert DCEF also led peri-implant bone trabecular area percentage increase in two time points. Histology results showed after loading electric field, it is visibly that the bone surrounding the implant surfaces extending to form a "pseudo-foot" structure grow along the implant surface morphology, new bone tissue and the implant surface adhered more closely in the experimental group than the control group.There are large number of new trabecular bone matrix and class trabecular bone in the implant surface and between trabecular bone mutual connection into the woven structure, the experimental group implant-bone interface has a uniform new bone tissue formation, in the control group implant-bone interface newborn loose bone tissue, the maturity of bone tissue and the connective degree with implant were slightly lower.Conclusion:DCEF can promote the migration of BMSCs, and enhance the bone mineral density around tibial implant in SD rat and promote osseointegration. |
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