Regulation Of Lithium Ions On Periodontal Regeneration And Related Fundamental Application

The movement of orthodontic tooth is completed by remodeling periodontal tissue under mechanical stress,the biomechanical effect of periodontal ligament plays a vital role.The cementum covering root surface is a layer of mineralized connective tissue,which is an important structure of periodontal attachment.Under physiological conditions,cementum,unlike bone,cannot reconstruct and remodel constantly and it has stronger anti-absorption ability than alveolar bone,these are all foundations of orthodontic tooth movement.However,under the damage condition,the cementum can hardly remodel because of much in organic salt in it.So how to improve the function of cementum attracts increasing attention,the results of this research have great significance for the repairment of orthodontic inflammatory root,but also have application value of the periodontal tissues reconstruction.Li Cl,as low toxic drug,has been already used in the treatment of mental illness widely for many years.In recent years,scholars have found that it can accelerate bone regeneration and attract widespread attention.However,current researchers put more focuses on its role in nerve cells and bone tissue rather than that in teeth and periodontal tissues.The effects and mechanism of Li Cl which acts on cementoblasts are still not very clear,in order to explore this problem,the following experiments are designed:1.Effects of lithium chloride on the function of cementoblasts.Objective:To investigated the effects of lithium chloride during the process of proliferation and differentiation.Methods: Murine immortalized cementoblasts cell line OCCM-30 was cultivated in this study.Lithium chloride conditioned medium was prepared at 10 m M,5m M,2.5m M,1.25 m M and 0m M concentration.A series of experiments including MTT analysis,cell staining,alizarin red staining,alkaline phosphatase(ALP)activity and Western blot were used to evaluate the proliferation and differentiation of cementoblasts.Protein expression including bone morphogenetic protein 2(BMP-2)were also checked to analyze changes in osteoclastogenesis.Results: There was no change on the cementoblasts proliferation and morphology of cells.It was no relations with the concentration and time-dependent of lithium ions.The expression of ALP was restrained by the concentration increasing of lithium ions.Alizarin red staining and quantitative analysis of the results also showed the same trend.Additionally,BMP-2 expression was also compared among different groups.The protein expression of cementoblasts was tested by Western blot.Cementoblasts expressed more BMP-2 protein with longer incubation times whether lithium was present or not.Conclusion: In summary,lithium exhibited no influence on cementoblast proliferation and inhibition on differentiation.BMP-2 downregulation was also involved in the process,suggesting a potential regulatory mechanism aside from Wnt signalling.Our results also indicated the distinct reaction of cementoblasts compared with osteoblasts toward the same agent.The results warrant further investigations.2.Effect of lithium ions on cementoblasts in the presence of lipopolysaccharide(LPS)in vitro.Objective: The aim of the present study,therefore,was to investigate the effect of lithium ions in the presence of LPS.Methods: A periodontitis model was induced in cementoblasts using lipopolysaccharide(LPS).The cytotoxic effect of the lithium ions on the cementoblasts was studied through the MTT assay.ALP analysis and alizarin red staining were performed to investigate the effect of the lithium ions on differentiation.To examine the effect of lithium ions on osteoclastogenesis,osteoprotegerin(OPG)and receptor activator of nuclear factor-?B ligand(RANKL)m RNA and protein expression levels were assessed using reverse transcription-polymerase chain reaction analysis and ELISA,respectively.Results: Compared with the effect induced by lithium ions on normal cementoblasts,proliferation and differentiation were downregulated following the co-incubation of the cementoblasts with LPS and lithium ions.Furthermore,the lithium ions appeared to alter osteoclastogenesis by regulating the OPG/RANKL ratio.Conclusion: The present findings suggest that lithium ions could downregulate proliferation and differentiation in a periodontitis model.Further studies should be undertaken prior to the acceptance of lithium ions for use in the clinic.Based on above studies,it can be inferred that lithium exhibited no influence on cementoblast proliferation and inhibition on differentiation.The results in combination have demonstrated that Li Cl may be beneficial to cementum protection via alleviating osteoclastogenesis.Li Cl can be regarded as the target to enhance the function of cementoblasts.With the deepening of the researches of Li Cl,it is expected to be one of the clinical drugs for the treatment of root absorption.3.The design and synthesis of the lithium ion-doped PGS scaffolds.Objective: To synthesized the lithium ion-doped PGS scaffolds by using the cell-specific properties of lithium ions.Methods:The lithium ion-doped PGS scaffolds were synthesized by adding lithium ions during the PGS crosslinking process.A series of experiments including FITR,ICP-OES,TGA,contact angle,SEM-EDS and weight loss were used to analysis the structural properties,lithium ion content,thermal properties,hydrophily,morphology,composition,porosity and degradation performance of the PGS-Li scaffolds.Results: The PGS-Li scaffolds has a similar composition and structure to the PGS scaffolds,basically meet the requirements of engineering scaffold materials,and The PGS-Li scaffolds has better hydrophilic and thermal stability than the PGS scaffolds.Conclusion: We constructed the PGS-Li scaffolds successfully,which provided a new idea for the regeneration of periodontal regeneration,especially of cementum.