The Study Of BMSCs Cell Sheets Aggregates To Promote Osteogenesis Around Dental Implants In Irradiated Bone

Background and objectives Implantation has become an important method for the repair of dentition defect.However,radiotherapy and other factors will cause damage to the bone tissue around the implant and cause the failure of implantation.At present,the method of improving implant osseointegration is mainly to modify the implant surface using physical and chemical modification.However,the effects are limited because the remodeling and regeneration ability of irradiated bone around implants is reduced due to the damage of cells and microvessels.In previous studise of our team,we used BMSCs sheets to wrap the Ti implants and make a MSCs-implant complex.More over,we tried to make a compound cell-sheets which consisted of BMSCs and endothelial progenitor cells.The results demonstrated that they had osteogenic ability in the irradiated bone.However,when the complex was put into bone,the MSCs cell sheets were easy to fall off or gathered in the upper part of the implants,which was difficult to repair large bone defect around implants.Platelet rich plasma has a lot of cell factors with the function of promoting osteogenesis and angiogenesis,which can be activated by calcium ion or thrombin.And it has been used in many studies of bone healing and regenration.This study focuses on the effect of post-radiotherapy for the implant osseointegration,aims to provide evidence for choosing appropriate dose of radiotherapy for patients who need radiotherapy after implantation.And in present study,BMSCs sheets fragments-PRP complex are prepared and injected into the bone defect around implants in irradiated bone,with the objective to find a promising method to promote bone repair and regeneration around implants in the irradiated bone.Methods: 1.To assess the proper dosage of post-implant radiotherapy which can cause damage to the osseointegration of implants,SD rats were irradiated using different dosage after implantation.Implant osseointegration were tested by Micro-CT analysis,hard tissue slices and pull-out test of implants.2.Using the whole bone marrow adherent method to isolate and culture BMSCs.BMSCs were identified using flow cytometry detection.And detect the osteogenic and adipogenic differentitation abilities by alizarin red staining and alizarin red staining.PRP were prepared from the fresh blood of rats.The effect of PRP on the proliferation of BMSCs was detected with CCK-8.Alkaline phosphatase staining and real-time quantitative PCR were used to detect the effect of PRP on the osteogenesis of BMSCs.3.The BMSCs sheets were cut into fragments,mixed with PRP and activated to form the BMSCs sheets fragments-PRP complex.The complex were injected into the space between implant and ?-TCP and then were put in the nude mices.After 8 weeks,the Micro-CT and hard tissue slices were used to detect the ectopic osteogenesis ability of the composite.4.To assess the bone regeneration of cell sheets fragments/PRP complexes in irradiated bone,rats were given radiotherapy of 20 Gy 4 weeks after implantation.BMSCs-PRP composite gel was injected into the bone defect around implants.After 8 weeks,test the bone formation around implants.Results 1.The results of Micro-CT and hard tissue slices showed that the bone tissue around implants was significantly reduced after high dose radiotherapy.Bone implant contact (BIC)and bone volume/total volume(BV/TV)were significantly lower than those of the non-radiotherapy group.2.BMSCs positively expressed MSCs markers.BMSCs could differentiate into osteoblasts and adipocytes,which demonstrated the BMSCs has the multipotent differentiation abilities.3.The 10% PRP gel can facilitate the proliferation of BMSCs.ALP staining and q PCR results show that PRP gel can induce BMSCs differentiate into osteoblasts.4.In the study of bone regeneration in nude mice,the BMSCs sheets fragments/PRP group showed significant new bone formation around dental implants,which was better than other groups.5.In the study of SD rats radiotherapy model,the results showed that the defect bone repair and new bone regeneration in the BMSCs sheets fragments/PRP group was better than the other groups.Conclusion 1.Radiotherapy has significantly negative effect on the osseointegration of implant.The osseointegration of implants decreased with the dose of radiotherapy increased.2.PRP can promote the proliferation and osteogenic differentiation of BMSCs.BMSCs sheets fragments-PRP composite gel can promote the regeneration of bone tissue around the implant.3.BMSCs sheets fragments-PRP complex can be used to improve the osteogeneration of the defect around dental implant in the irradiated bone.