成骨细胞对梯度拉伸应变的响应

采用四点弯曲加载装置对原代的大鼠颅盖骨细胞施加周期性的拉伸刺激，并设计了应变呈梯度增加的加载方式，使成骨细胞受到的拉伸应变为500－1500με，每隔2h增加500με，以考察成骨细胞对变化的力学环境的响应。结果表明，在500με下拉伸2－6h促进了成骨细胞的增殖、碱性磷酸酶活力增强和胞外钙基质沉积。对细胞施加应变呈梯度增加的拉伸刺激，则发现当应变从有利于细胞的生长分化水平（500με）变化为不利于细胞生长分化的水平（1000με，1500με）后，细胞的增殖指数、碱性磷酸酶活力和胞外钙基质分泌量都迅速降低，以适应新的力学环境。说明成骨细胞能够分辨不同的应变水平，并相应地调节自身的生理功能，从而表现出对变化的力学环境的适应。

THE PHYSIOLOGICAL RESPONSE OF OSTEOBLASTS TO A GRADIENTLY INCREASED STRETCHING

A four-point bending apparatus was used to apply a cyclic stretching to osteoblasts derived from Wistar calvaria. In order to investigate the responses of osteoblasts to the changing mechanical environment, a new loading method, the gradiently increasing stretching was also designed. The strain magnitude which cells were loaded was increased by 500 με every 2 h. The results showed that stretching at 500 με for 2~6 h increased the proliferation, ALP activity and extracellular calcium secretion of osteoblasts. On the contrary, stretching at 1000 με and 1500 με inhibited the proliferation, ALP activity and extracellular calcium secretion. When cells were stimulated by gradiently increased loading, the proliferation index, ALP activity and extracellular calcium synthesis decreased rapidly as the stimulation was changed from an optimal stretching (500 με) to an inhibitive stimulation (1000 με, 1500 με). The results suggested that osteoblasts can distinguish between different strain magnitudes and regulate their physiological functions to adapt to the changing mechanical environment.