Department of Biomedical Engineering, Yonsei University, Gangwon Do, Korea.
BMC Musculoskelet Disord. 2009 Sep 4;10:109. doi: 10.1186/1471-2474-10-109.
Oscillatory fluid flow (OFF)-induced shear stress leads to positive bone remodeling through pro-formative and anti-resorptive effects on bone cells. In this study, the effects of high frequency OFF on expression of receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG), two important regulators of osteoclast differentiation, were investigated.
Cells were exposed to 1 Pa peak shear stress using three loading frequencies (1, 10, and 20 Hz) widely employed in cell, animal, and clinical studies of bone remodeling. Two separate experiments were performed where either the total number of cycles (3600 cycles) or the total loading time (60 min) was kept constant. Real-time RT-PCR was used to quantify mRNA levels of RANKL, OPG.
3600 cycles of OFF at 1 Hz and 10 Hz loading decreased RANKL/OPG ratio. Interestingly, these results were due to different mechanisms where at 1 Hz the decrease was due to an increase in OPG mRNA, whereas at 10 Hz the decrease was due to a decrease in RANKL mRNA.
Although high frequency OFF does not appear to further enhance the decrease in the RANKL/OPG ratio, these results suggest a potential to differentially control the change in either RANKL or OPG mRNA expression by applying different loading frequencies.
振荡液流（OFF）诱导的切应力通过对成骨细胞的促形成和抗吸收作用导致正性骨重塑。在这项研究中，研究了高频 OFF 对核因子-κB 配体受体激活剂（RANKL）和骨保护素（OPG）表达的影响，这两种物质是破骨细胞分化的重要调节因子。
细胞分别暴露于频率为 1、10 和 20 Hz 的三种加载频率（1 Pa 峰值切应力），这三种频率广泛应用于骨重塑的细胞、动物和临床研究。进行了两项单独的实验，其中一项实验保持总的循环次数（3600 次）不变，另一项实验保持总的加载时间（60 分钟）不变。实时 RT-PCR 用于定量 RANKL、OPG 的 mRNA 水平。
1 Hz 和 10 Hz 加载的 3600 个 OFF 循环降低了 RANKL/OPG 比值。有趣的是，这些结果是由于不同的机制导致的，在 1 Hz 时，增加了 OPG mRNA，而在 10 Hz 时，降低了 RANKL mRNA。
虽然高频 OFF 似乎不会进一步增加 RANKL/OPG 比值的降低，但这些结果表明，通过应用不同的加载频率，有可能有潜力分别控制 RANKL 或 OPG mRNA 表达的变化。
