Inhibitory effects of strontium on osteoclatogenesis induced by titanium particles

Abstract

Objective To observe the effect of strontium (Sr2+) on titanium (Ti) particles()nduced osteoclastgogenesis from a murine macrophage cell line (RAW264.7) in the presence of receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL).Methods The experiment involved 5 groups:black group,Ti group,R group,R +Ti group and Sr2+ group.The effect of Ti particles and (or) Sr2+ on RAW264.7 cell viability was measured by using the cell counting kit-8.Tartrte resistant acid phosphataae (TRAP) staining was ()used to analyze the osteoclast formation.Quantitative real-time reverse transcriptionpolymer() chain renction (RT-PCR) was used to detect the mRNA levels of cathepsin K (Cath-K) calcitonin receptor (GTR),matrix metalloproteinase-9 (MMP-9) and TRAP,The inhibitory κBα (IκBα) in NF-κB signaling pathway was determined by Westem blotting,Results Sr2+ (0.5,1.0,2.0,5.0,and 10.0 mmol/L) did not affect the Hability of RAW264,7 cells cuhured with Ti particles,The mature osteoclaits were obtained from RAW264,7 cells cultured with RANKL and Ti partic les for 5 days and detec ted by TRAP staining.The number of TRAP positive cells in 5 mmol/L Sr2+ was (323.33 ± 43.84)/well,which was significantly dec reased as compared with R group [(453.33 ± 33.99)/well] (P ＜ 0.05),RT-PCR demonstrated that mRNA levels of Cath-K,CTR,MMP-9 and TRAP wew significantly greater in medlum with RANKL and Ti particles than without RANKL and Ti particles.When 5 mmd/L Sr2+ was added to the culture system for 5 dsays,the mRNA levels of Cath-K,TRAP,MMP-9 and CTR respectively were 2.76 ±0.66,2.69 ±0.57,2.10 ±0.34 and 1.72 ±0.32,in combination with RANKL and Ti particles (7.97 ± 0.77,10.10 ± 1.18,7.37 ± 1.02 and 5.55± 0.53) (P ＜ 0.05).The resul of Western hlotting showoed that the levels of IκBα were reduced at 15 min but inc reased again at 180 min after Ti particle treatment,Pretreatment with Sr2+ significantly inc reased the expression of IκBα in response to Ti partiele,Conelualon This study provides evidence that Sr2+ can markedly inhibit Ti pmic le-induced osteoclastogenesis by the down-regulation of NF-κB signaling pathway,and is a promisingly therapeutic candidate for the wear particle-induced osteolysis. Key words: Strontium; Osteoclast; Titanium particle; Nuclear factor-κB