Effects of stretch on cell proliferattion of fibroblast and collagen metabolism

虽然真皮成纤维细胞接受肌肉运动所施加的拉伸和松弛，但机械力对细胞的生物学效应仍不清楚。本研究采用计算机控制的双轴拉伸装置加载皮肤成纤维细胞，观察拉伸和松弛对皮肤成纤维细胞增殖和分化的影响。使细胞经受循环S形拉伸和松弛，6个循环/分钟，最大变化为10%。与非应变细胞相比，应变细胞的细胞数量增加，转化生长因子-β1（TGF-β1）对应变诱导的细胞增殖刺激有额外作用。免疫印迹分析显示，无论TGF-β1是否促进细胞α-平滑肌肌动蛋白（SMA）的表达，周期性牵张均使其表达水平降低。流式细胞术表明，所有细胞，无论是否用TGF-β1刺激，响应于应变SMA表达减少。免疫荧光显微镜显示，有星形，铺展细胞的SMA和梭形细胞的SMA是阴性或轻微阳性的高度阳性，和前者的比例，后者的响应周期应变减少。条件培养基形式的细胞经受循环应变对非应变细胞的细胞增殖和SMA表达均无影响，表明应变诱导的效应不通过自分泌机制来介导。染料木黄酮取消菌株对细胞增殖的刺激作用和对SMA表达的抑制作用，而星形孢菌素或百日咳毒素没有。这些数据表明，应变对细胞增殖和SMA表达的影响是通过酪氨酸激酶依赖机制介导的。

Although dermal fibroblasts receive stretch and relaxation exerted by muscle movement, biological effects of the mechanical force on the cells remains unclear. In the present study to assess effects of stretch and relaxation on cell proliferation and myofibroblast differentiation of dermal fibroblasts, cells were loaded in a biaxial strain device, which was controlled with computer. Cells were subjected to cyclic sigmoidal stretch and relaxation six cycles/min with 10% maximum change. Cell number was increased in strained cells compared with non-strained ones, and transforming growth factor-β1(TGF-β1)showed an additional effect to the strain-induced stimulation of cell proliferation. Immunoblot assay showed that level of α-smooth muscle actin(SMA)expression of cells , either enhanced by TGF-β1 or not, was decreased by cyclic strain. Flow cytometry suggested that all cells, either stimulated with TGF-β1 or not, decrease the SMA expression in response to strain. Immunofluorescence microscopy showed that there were star-like, spreaded cells that were highly positive for SMA and spindle cells that were negative or slightly positive for SMA, and that a ratio of the former cells to the latter ones was decreased in response to the cyclic strain. Conditioned medium form cells subjected to the cyclic strain had no effects on both cell proliferation and SMA expression of non-strained cells, indicating that the strain-induced effects are not medicated through autocrine mechanism. Genistein abolished both the stimulatory effect of strain on cell proliferation and its suppressive effect on SMA expression, whereas staurosporine or pertussistoxin did not. These data indicatethat the strain-induced effects on both cell proliferation and SMA expression are mediated by tyrosine kinase-dependent mechanism.