周期性张应变作用下成骨细胞凋亡的体外研究

目的 研究机械周期性张应变对体外培养的成骨细胞凋亡的作用及其与细胞增殖和细胞分化之间的关系。方法 酶消化法分离培养新生SD大鼠颅顶骨成骨细胞，P2-P4代成骨细胞培养2d和4d后，用无血清培养法诱导成骨细胞凋亡，同时使用Flexcell 4000TM加力系统分别对细胞施加72h变形率为6%和13.6%的等轴循环牵张力。根据总培养时间分为5d和7d两组。运用流式细胞技术对成骨细胞凋亡水平进行检测，同时作细胞记数及碱性磷酸酶（ALP）蛋白含量检测。结果 与不加力的对照组相比，6%牵张力下5d组成骨细胞凋亡率下降了45%，成骨细胞数量增加了34%。在13.6%牵张力下7d组成骨细胞凋亡率增加了192%，细胞数量下降了64%。ALP活性在两种力值大小的牵张力刺激下均有下降。结论 周期性张应变对成骨细胞的凋亡有影响，不同力值大小的牵张力可通过促进或抑制细胞凋亡的方式调控成骨细胞的活性。

Study on osteoblast apoptosis in response to mechanical stretch in vitro

Objective To investigate the effect of mechanical stretch force on the apoptosis, proliferation and differentiation of osteoblast culture in vitro. Methods Rat calvarial osteoblasts passage 2 to 4 were used and cell apoptosis was induced by serum starvation after 2 or 4 days of static culture. The osteoblasts were then subjected to 72 hours of cyclic equibiaxial stretch forces using Flexcell 4000TM strain unit. Apoptotic levels of the osteoblasts were quantified by flowcytometer right after the stretch application. The cell number and alkaline phosphatase (ALP) activity were also evaluated. Results After 2 days culture, 6% elongation of stretch force led to a 45% decrease of apoptosis rate, with a 34% increase of cell number. After 4 days culture, 13.6% elongation of stretch force elicited 192% increase of osteoblast apoptosis, while the cell population was decreased by 64%. ALP activity was declined upon the two magnitudes of force loading. Conclusions Stretching force can affect apoptosis in osteoblast culture. This regulative effect was magnitude sensitive controlling the osteoblast activity.