流体剪应力对成骨细胞OPG和ODF表达的影响

通过平板流动腔装置对大鼠成骨细胞施以流体剪应力,研究剪应力作用对成骨细胞中骨保护因子(osteoprotegerin,OPG),破骨细胞分化因子(osteoclast differentiation factor,ODF)基因表达的影响.分别考察了剪应力大小和作用时间,以及单一水平和梯度变化的剪切力加载方式的影响.运用RT-PCR和蛋白质印迹技术检测OPG、ODFmRNA和蛋白质表达的变化,结果显示,剪切力作用下OPG的表达得到促进,ODF的表达受到抑制,mRNA与蛋白质表达的变化一致,这种影响与剪切力的大小和作用时间有关.1.0和1.5N/m2的剪应力作用效果比0.5N/m2明显,梯度变化的作用方式在作用效果上与最后一个梯度水平相当的恒定剪应力单独作用没有显著差异,在加载的24h内剪应力对OPG、ODF表达的影响始终存在.这种影响使得OPG/ODF的平衡向着OPG占优的方向发展,这种变化意味着骨吸收会受到抑制,提示力学刺激可能通过OPG/ODF调控系统对骨代谢平衡进行调控.

Effect of Fluid Shear Stress on Expressions of OPG and ODF in Osteoblasts

Gene expression and protein synthesization of osteoprotegerin (OPG) and osteoclast differentiation factor (ODF) were studied in shear stress cultured osteoblasts applying parallel-plate flow chamber system. Shear stress of 0.5, 1.0, 1.5 N/m2 in 24 h, and step-wise increased shear stress from 0.5 to 1.0 and then to 1.5 N/m2 and each stress for 8 h, and stepwise decreased shear stress from 1.5 to 1.0 and then to 0.5 N/m2 and each stress for 8 h were applied. The expression of OPG and ODF mRNA was detected by RT-PCR, and synthesization of their protein was detected by Western blot. The results showed that the shear stress of 1.0 and 1.5 N/m2 induced more significant changes in OPG mRNA and ODF mRNA than 0.5 N/m2 and there was no significant difference between 1.0 and 1.5 N/m2. No marked differences were observed between the effects of step-wise increased shear stress and 1.5 N/m2 after 24 h, and the same was between the effects of step-wise decreased shear stress and 0.5 N/m2 after 24 h. The shear stress of 1.0 N/m2 increased OPG expression and inhibited ODF expression in 24 h both in mRNA and protein level. In all, the ratio of OPG and ODF was increased by shear stress, which reminds that bone resorption was inhibited by the fluid flow, and shear stimuli regulated the new balance of bone resorption and bone formation throught OPG/ODF route.