中文摘要：

背景：临床运用牵张成骨技术时常用的加力方式有2种：持续加力和间歇加力。但是,哪种方式更有利于新骨形成尚有争议。目的：观察持续加力和间歇加力对骨髓基质干细胞分化及增殖能力的影响。方法：密度梯度离心法分离培养兔骨髓基质干细胞,传至3代接种至6孔细胞培养板进行力学实验。空白组不作离心处理,静态培养;持续加力组每天加载离心4 h（1 100 r/min,相对离心力20×g）;间歇加力组每次加载离心力24 min（1 100 r/min,相对离心力100×g）,每天4 h内2次,2 h加力1次。力学刺激3 d停止培养,检测细胞增殖活性、碱性磷酸酶活性、骨钙素水平。结果与结论：（1）与空白组比较,机械离心力能促进骨髓基质干细胞成骨分化和增殖,增强碱性磷酸酶活性（P〈0.05）;（2）持续加力较间歇加力对骨髓基质干细胞分化增殖及碱性磷酸酶活性影响更显著（P〈0.05）。

英文摘要：

BACKGROUND：In the process of distraction osteogenisis, continuous and intermittent force can be used. However,which one is more beneficial for bone formation is still controversial.OBJECTIVE：To investigate and compare the effect of continuous and intermittent force on the proliferation and differentiation of bone marrow stromal stem cells （BMSCs）.METHODS：Rabbit BMSCs were obtained using density gradient centrifugation method. The passage 3 BMSCs were seeded onto 6-well cell culture plates for mechanical investigation. Then, the cells were randomly divided into three groups. Group A was a control group without any treatments. Group B was the continuous force group with a centrifugal force （1100 r/min, relative centrifugal force 20＆#215;g） applied 4 hours per day. Group C was the intermittent group with an centrifugal force （1100 r/min, relative centrifugal force 100＆#215;g） applied twice in 4 hours and lasting 24 minutes once. After 3 days of culture under mechanical force, the proliferation of BMSCs and the expression of alkaline phosphatase and osteocalcin were detected and compared.RESULTS AND CONCLUSION：The centrifugal force promoted the ostegenic differentiation and proliferation of BMSCs and the expression of alkaline phosphatase significantly increased compared with the control group （P 〈 0.05）.Compared with the intermittent force, the continuous force showed better effect on osteogenic differentiation and proliferation of BMSCs as well as the activity of alkaline phosphatase （P 〈 0.05）.