Effect Of FGF23 On Osteoclasts Differentiation And Function

Osteoclasts(OCs)play a key role in maintaining the morphology of animal bones in the process,which mainly degrade inorganic and organic bone,and regulate osteoblasts(OBs)to participate in bone reconstruction directly or indirectly.OC is the unique cell with bone resorption function,and once abnormally secreted,it will cause various bone metabolism related diseases,the most common of which is osteoporosis.In recent years,Fibroblast growth factor 23(FGF23)was found as an important factor regulated calcium and phosphorus homeostasis.It has been reported that FGF23 participate in bone metabolism,and abnormal FGF23 level could cause metabolic bone disease.But until now,the exact effect of FGF23 on bone metabolism and its mechanism is not clear,the purpose of this study is to elucidate the effect of FGF23 on the differentiation and function of OC,the results will provide new ideas for preventing metabolic bone disease caused by FGF23.In this study,the culture system of OC in vitro was established by RAW264.7 treatmented with 50ng/mL RANKL and 30 ng/mL M-CSF.TRAP staining,TRAP activity,bone resorption activity,and mRNA expression levels of Fgfrs,Klotho,bone resorption-related factors(Atp6i,CtsK,Trap,Mmp-9),osteoblast-associated factors(Bmps,Sphk1,PDGF-bb)were detected in the 3rd,5th,7th,and 9th days.Experimental results showed:1.Adding 50 ng/mL RANKL and 30 ng/mL M-CSF to RAW 264.7with a concentration of 10~4 cells/mL,we acquired a large number of OCs with TRAP activity on the 7th day,which indicated that OC culture system was successfully established.2.FGF23 can increase OC number and enhance OC TRAP activity,indicating FGF23 can promote the differentiation of OCP into OC.3.FGF23 can increase the mRNA expression levels of Fgfr1,Fgfr3,Fgfr4 and Klotho,indicating FGF23 can regulatory effect on OC through the FGFRs-Klotho pathway.4.FGF23 can stimulate OC bone resorption activity and increase mRNA expression levels of bone resorption-related factors Atp6i,CtsK,Trap and Mmp-9.5.FGF23 can increase the mRNA expression levels of Bmp2,Bmp6,Bmp7 and Sphk1,increase the mRNA expression levels of PDGF-bb in the early stage of OC differentiation,decrease the mRNA expression levels of PDGF-bb in the later period.These results indicated that FGF23 can promote the differentiation of RANKL and M-CSF induced OCP to OC,improve the activity of bone absorption and indirectly regulate the activity of OB through the FGFRs-Klotho pathway.