机械应力对C57BL/6小鼠成骨细胞分化和凋亡的影响

The Effect of Mechanical Strain on Differentiation and Apoptosis of Osteoblasts in Mice

目的:研究不同强度和时间的牵张应力对C57BL/6小鼠成骨细胞分化和凋亡的影响。方法:提取C57BL/6小鼠成骨细胞,采用Flexcell-FX5000系统,分别对细胞进行3%、6%和12%的形变幅度的正弦波应力刺激,时间分别为2 h、4 h、8 h、12 h。干预结束后检测细胞的ALP活性,流式细胞仪检测细胞的凋亡率。结果:3%和6%强度牵张干预后,成骨细胞ALP活性升高(P<0.05),分别在8 h和4 h升高幅度最大,而在12 h又出现下降趋势。12%强度刺激2 h ALP小幅上升(P>0.05),之后出现下降趋势,于12 h活性最低。另外,6%强度牵张时,细胞凋亡率先下降,后随着时间的延长而升高;3%和12%强度牵张时,细胞凋亡率随着时间的延长而升高,3%强度牵张8 h才出现早期凋亡的升高,而12%强度牵张4 h即出现细胞凋亡,以晚期凋亡为主。结论:机械牵张应力可以促进成骨细胞分化,以6%强度干预4~8 h为宜。同时,6%强度牵张4 h细胞的凋亡率最低,增大牵张强度或者延长干预时间都会导致细胞凋亡率增加。

Objective To investigate how different magnitudes and durations of mechanical strains af-fect the osteoblast differentiation and apoptosis in C57 BL/6 mice. Methods Osteoblast cells were isolat-ed from fetal C57 BL/6 mice, and loaded with cyclic mechanical strains with magnitude of 3%, 6% and12% for 2 h, 4 h, 8 h and 12 h respectively. After the intervention, the ALP activity assay was con-ducted, and the cell apoptosis was detected using the flow cytometry. Results The mechanical strainwith the magnitude of 3% and 6% increased ALP activity of osteoblasts（P〈0.05）, which reached thehighest efficacy at 4 h and 8 h, followed by a downward trend at 12 h. The mechanical strain with themagnitude of 12% increased ALP activity slightly at 2 h, followed by a decrease till the lowest pointat 12 h. Moreover, the 6% magnitude mechanical strain decreased the cell apoptosis at 4 h and thenincreased it at 8 h and 12 h. Both 3%-and 12%-magnitude mechanical strains increased the cellapoptosis with the extension of time. The 3% magnitude induced mainly the early apoptosis at 8 h andthe secondary apoptosis at 12 h, while the 12% magnitude induced apoptosis at 4 h, mainly secondaryapoptosis. Conclusion Mechanical strain can promote the osteoblast differentiation of the optimal effectwith the magnitude of 6% and duration of 4 to 8 hours. The 4-hour mechanical strain with magnitudeof 6% leads to the minimum rate of apoptosis. Either higher magnitude or longer duration will increase the apoptosis.