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尚不清楚。在本研究中，为了评估拉伸和放松对真皮成纤维细胞增殖和肌成纤维细胞分化的影响，我们将细胞置于计算机控制的双轴应变装置中。细胞进行6次周期/min的s形拉伸和松弛，最大变化幅度为10%。与非张力细胞相比，张力细胞的细胞数量增加，转化生长因子-β1（TGF-β1）在张力诱导的细胞增殖刺激中表现出额外的作用。免疫印迹检测结果显示，TGF-β1增强或未增强的细胞α-平滑肌肌动蛋白（SMA）表达水平均被循环菌株降低。流式细胞术显示，无论TGF-β1刺激与否，所有细胞在应变作用下SMA表达均降低。免疫荧光显微镜观察发现，SMA呈高阳性的星形扩散细胞和SMA呈阴性或微阳性的纺锤形细胞，且前者与后者的比例随循环应变的变化而降低。经循环菌株处理的条件培养基细胞对非应变细胞的细胞增殖和SMA表达均无影响，表明菌株诱导的效应不是通过自分泌机制发挥作用的。染料木素可以消除菌株对细胞增殖的刺激作用和对SMA表达的抑制作用，而staurosporine和百日咳毒素则没有。这些数据表明，菌株对细胞增殖和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.