中文摘要：

目的：研究不同力值及加力时间的机械牵张应力对成骨细胞增殖和分化能力的影响。方法：采用Flexcell牵张应力加载系统,对成骨样细胞Saos-2进行不同力值、不同时间的刺激,MTT法检测细胞受力后的增殖变化;ALP试剂盒检测细胞受力后ALP活性的变化;半定量RT-PCR检测骨钙蛋白（OC）、骨桥蛋白（OPN）的mRNA的表达;用茜素红染色观察矿化结节形成。结果：当应变值为12%时,力学刺激对成骨样细胞Saos-2增殖以及ALP活性的促进作用最强（P〈0.01）。应变值为12%的力学刺激呈时间依赖性明显上调了成骨样细胞Saos-2的增殖、ALP活性以及骨桥蛋白和骨钙蛋白mRNA的表达（P〈0.01）;牵张应力刺激组较对照组更加容易形成矿化结节。结论：大小适宜的牵张应力可以促进成骨细胞的增殖以及分化指标如ALP活性、骨桥蛋白和骨钙蛋白mRNA的转录水平、矿化结节的形成等,说明机械牵张应力对于成骨细胞的增殖和分化发挥着重要的调控作用。

英文摘要：

Objective：To investigate the effects of mechanical strain on proliferation and differentiation of Saos-2 osteoblastic cells.Methods：Saos-2 osteoblastic cells were subjected to elongation by using Flexcell strain loading system simultaneously.MTT colorimetric method was used to assess cellular proliferation;Biochemical analysis was used to study the effects of mechanical strain on alkaline phosphatase（ALP）activity;semi quatative RT-PCR was used to examine mRNA level of osteocalcin and osteopotin.Alizarin Red-S method was used to study the mineralization of Saos-2 osteoblastic cells.Results：The proliferation and ALP activity of Saos-2osteoblastic cells were significantly increased after mechanical strain treatment.12% elongation rate showed the strongest stimulatory effects（P〈0.01）.The expression of OC,OPN mRNA and the formation of mineralization nodules in Saos-2osteoblastic cells were promoted by 12% mechanical strain elongation rate.Conclusion：Our data indicated that mechanical strain stimulation increased the proliferation and differentiation markers such as ALP activity,mRNA expression level of OC and OPN,and the formation of mineralization nodules in Saos-2osteoblastic cells.Mechanical strain may play a very important role in proliferation and differentiation of osteoblasts.