中文摘要：

背景：研究证实力学刺激是影响骨改建的重要因素，可促进骨髓基质干细胞骨向分化；但不同幅度力学刺激对骨髓基质干细胞分化的影响尚不明确。目的：观察持续张应力对大鼠骨髓基质干细胞成骨分化的影响。方法：全血贴壁培养法秋取大鼠骨髓基质干细胞。采用Flexercell-4000细胞体外应力加载系统对骨髓基质干细胞施加5％，10％，15％幅度的持续张应力，对照组则不加力培养，频率1Hz，持续时问48h。分刖在加力后1，6，12，24，48h检测成骨标记物碱性磷酸酶、I型胶原、骨钙素mRNA及成骨特异性转录因子Runx2的mRNA及蛋白表达。结果与结论：5％和10％持续张应力作用下，骨髓基质干细胞的成骨标记基因碱性磷酸酶、I型胶原、骨钙素mRNA的表达较对照组升高（P〈0．05），10％张力组升高的时间均较5％张力组早、幅度较高。15％持续在加力6h时可促进骨髓牲质干细胞碱性磷酸嗨、I魁胶原mRNA的表达（P〈0．05）、随后表达下降，加力48h后上述指标均低于对照组（P〈0．05），骨钙素mRNA的表达加力6h后均低于对照组（P〈O．05）。5％张力组仅加力24h后骨髓基质干细胞Run×2蛋白表达高于对照组（P〈0．05），10％，15％张力组加力6h后Run×2蛋白表达均高于对照组（P〈0．05）。结果证实，5％，10％，15％持续张应力均可更有效地促进骨髓基质干细胞的骨向分化，10％持续张力的促进效应更显著。

英文摘要：

BACKGROUND： Mechanical stimulation can promote the osteogenic differentiation of bone marrow stromal cells, but the effect of different magnitude of tensile stress on the bone marrow stromal cells is not clear. OBJECTIVE： To study the effect of different magnitudes of continuous tensile stress on the osteogenic differentiation of rat bone marrow stromal cells. METHODS： Rat bone marrow stromal cells were obtained and purified by full-blood attachment culture. The 5%, 10% and 15% continuous tensile stress （1 Hz） were strained on bone marrow stromal cells with Flexercell-4000 mechanical loading system and lasted for 48 hours, and the cells in the control group were cultured without stress. The mRNA and protein expression of osteoblast-related genes alkaline phosphatase, collagen type } , osteocalcin and osteoblast-specific transcription factor Runx2 were analyzed at 1, 6, 12, 24 and 48 hours after strain. RESULTS AND CONCLUSION： The mRNA expression of alkaline phosphatase, collagen type ｜ and osteocalcin was increased in rat bone marrow stromal cells subjected to 5% and 10% continuous tensile stress when compared with the control group （P 〈 0.05）, but the 10% tensile stress group increased earlier than the 5% tensile stress group, and the amplitude was higher. The mRNA expression of alkaline phosphatase and collagen type I was increased at 6hours after 15% elongation （P 〈 0.05）, and then decreased gradually. At 48 hours after continuous tensile stress, the indicators above were lower than those in the control group （P 〈 0.05）. The expression of Runx2 protein in bone marrow stromal cells at 6 hours in 15% elongation was higher than that in the control group （P 〈 0.05）, so did the 5% and 10% elongation groups （P 〈 0.05）. It indicates that 5%, 10% and 15% tensile stress can promote the osteogenic differentiation of bone marrow stromal cells, and 10% tonsile stress has the most significant effect.