Fibroblast growth factor 23 expression in rat calvarial osteoblastic cells and its responses to hormones in vitro

Objective To investigate the expression patterns of fibroblast growth factor 23(FGF23) in osteoblast and its responses to calcium,phosphate,exogenous PTH and 1,25(OH)2D3. Methods The primary rat calvarial osteoblasts were cultured in MEM medium which containing 10% FBS,then were harvested when cells were in half-confluence,confluence,osteoid deposition and osteoid mineralization stages respectively.The procedure was monitored under microscopy.Total RNA was extracted from cells according to the Trizol procedure.FGF23 mRNA levels were determined by Real-time PCR.Further,the confluent osteoblasts were treated with 3.2 mmol/L CaCl2,4.4 mmol/L β-glycerophosphate,10-9 mol/L rhPTH(1-34) and 10-8 mol/L 1,25(OH)2D3 respectively for 3 days,and same volume of the medium was added as the control.The gene expressions were determined by Real-time PCR. Results FGF23 expression was transiently up-regulated at cell confluent stage and down-regulated after that.The FGF23 mRNA levels were 7.5-fold higher in confluent cells compared with that in half-confluent cells(P0.001).The markedlly stimulating effect(about 16 times) on FGF23 expression was stimulated by exogenous 1,25(OH)2D3 treatment while no significant effect was found on FGF23 mRNA levels by CaCl2,β-glycerophosphate,and rhPTH(1-34) treatments when compared with the control. Conclusions The FGF23 expression in osteoblast is developmental stage-related and its powerful stimulator is 1,25(OH)2D.