中文摘要：

背景：目前对于牵张成骨促进间充质干细胞-成骨细胞系迁移的机制尚未明了，亟需基于这一机制的新的治疗方案，以提高牵张成骨临床疗效。目的：观察牵张应力下间充质干细胞-成骨细胞系mTOR信号通路相关基因的表达以及细胞迁移能力。方法：将12只SD大鼠随机分为2组：牵张组大鼠（n=6）进行右侧下颌骨牵张成骨，非牵张组大鼠（n=6）行同侧下颌骨截断后安置牵张器但不牵张，术后15 d进行免疫组织化学染色分析新生骨痂中p-mTOR表达变化。另外，对培养的健康SD大鼠下颌骨间充质干细胞进行体外牵张试验，施加（6%，4 h）的静息牵张力，对照组不施加牵张力，实时定量PCR、划痕实验等方法检测间充质干细胞-成骨细胞系mTOR信号通路相关基因的表达及细胞迁移能力的变化。结果与结论：牵张组大鼠新生骨痂中的p-mTOR表达高于非牵张组（P 〈0.05）。与非牵张组（0%，4 h）相比，牵张组（6%，4 h）间充质干细胞-成骨细胞系的 mTOR、Raptor、p70S6K、MMP-2、MMP-9、MMP-13基因表达升高，间充质干细胞-成骨细胞系迁移距离更远（P 〈0.05）。结果提示牵张应力可能通过激活间充质干细胞-成骨细胞系的mTOR/MMPs信号通路，促进其迁移。

英文摘要：

BACKGROUND：Distraction osteogenesis is one of the most important tissue engineering technologies. However, the exact signaling pathway controling mesenchymal stem cel-osteoblast lineage （MSC-OB） migration during distraction osteogenesis has not yet been elucidated. More efforts should be paid to make a ful understanding of the mechanism on MSC-OB lineage migration, which can improve the clinical efficacy of distraction osteogenesis. OBJECTIVE：To evaluate the effects of mechanical stretch on the ability of MSC-OB mobility and expression of mammalian target of rapamycin （mTOR） signaling pathway as wel as matrix metaloproteinases （MMPs） in MSC-OB, and to make clear the mechanism by which controls MSC-OB migration during distraction osteogenesis. METHODS：Twelve Sprague-Dawley rats were randomized into two groups： experimental group （n=6）, anin vivo＆nbsp;rat mandibular distraction osteogenesis model was established on the right side of rats; non-stretch group （n=6）, only the mandibular resection was done but with no distraction osteogenesis. Immunohistochemical staining was used to detect phosphorylated mTOR expression in new osteotylus at 15 days after operation. In addition, an in vitro cel stretch model was made in the mandibular mesenchymal stem cels from healthy Sprague-Dawley rats under resting tension force （6%, 4 hours）; no distraction was done in control group. The ability of MSC-OB mobility, the expression of mTOR, Raptor, p70S6K and MMPs were evaluated using experiment methods including immunohistochemistry staining, real-time PCR and scratch assay. RESULTS AND CONCLUSION： The expression of phosphorylated mTOR in MSC-OB was upregulated in the mandibular bone calus of the stretch group than the non-stretch group （P 〈 0.05）. In thein vitro experiments, MSC-OB applied with mechanical stretch （6%, 4 hours） showed elevated gene expression levels of mTOR, Raptor, p70S6K, MMP-2, MMP-9 and MMP-13 compared with the control group （0%, 4 hours）. Meanwhile, MSC-OB in