Effect of Sodium Fluoride on the Expression of Osteoprotegerin to Receptor Activator of NF-kappa B Ligand mRNA in Mouse Osteoblasts in vitro

The receptor activator of nuclear factor kappa B ligand(RANKL) and its decoy receptor,osteoprotegerin(OPG),play an important role in bone metabolism,which directly control osteoclastogenesis.Here we investigate the expression of OPG and RANKL mRNA using an in vitro osteoblast culture assay.The osteoblasts were derived from mouse calvarial bone and isolated by complete trypsinization and collagenase digestion and cultured in DMEM supplemented with 15% FBS at 37℃ containing 5% CO2,and the osteoblasts were exposed to the different concentrations of sodium fluoride(0,10-12,10-11,10-10,10-9 and 10-8 mol/L) for 40 h at 37℃ containing 5% CO2,and the total RNA was extracted and reverse transcribed into first-strand cDNA.The cDNA was amplified using OPG,RANKL and β-actin primers by real-time fluorescent quantitative PCR(FQ-PCR) in DNA Engine OpticonTM2 continuous fluorescence detection system.The results indicated that OPG mRNA expression of mouse osteoblasts in sodium fluoride treated groups were up-regulated and the RANKL mRNA expression also increased excepting the group of 10-12 mol/L sodium fluoride.When exposed to sodium fluoride of 1.0×10-12 to 1.0×10-8 mol/L,the relative expression level of OPG/RANKL mRNA was also up-regulated.Particularly the ratio of OPG/RANKL increased significantly from 1.0×10-12 to 1.0×10-10 mol/L sodium fluoride(P0.01).Thereafter,it was decreased gradually from 1.0×10-10 to 1.0×10-8 mol/L sodium fluoride(P0.05).In conclusion,these in vitro data demonstrated that traces of sodium fluoride could decrease osteoclastogenesis.