A cell-stretching system as a model system for the study of biomechanics

1.为了阐明体外培养系统中机械应力对细胞的影响，我们研制了一种可以长时间重复单向拉伸细胞培养底物的培养系统。2.由于肌细胞是在机械活动的环境中形成和维持的，以肌细胞为模型，研究了机械应力对培养细胞的影响，观察到了拉伸引起的两个显著现象：1)依赖拉伸的细胞排列和2)肌细胞肥大：1)在标准条件下培养大鼠主动脉平滑肌细胞(A10)和小鼠C2成肌细胞，然后以1 Hz的频率以20%的幅度重复拉伸，细胞与拉伸方向成约70度角取向。肌动蛋白细丝al…在相同的方向上取向更多，但灯丝取向先于细胞取向。我们发现，拉伸激活离子通道的抑制剂100 mM Gd和放线菌亚胺完全阻断了这种拉伸依赖的细胞取向，但这些试剂根本不影响细丝的重新取向。从这些结果可以得出结论，细丝的取向和细胞的取向密切相关，但调节不同。2)就肌肉细胞(肌管)而言，从生理角度看，沿细胞纵轴的伸展是重要的。由于在沿沟槽排列的肌管拉伸过程中没有发生细胞取向的重排，所以可以在纵向细胞轴的方向上拉伸肌管超过一周。我们观察到，与未拉伸培养的对照组相比，肌管直径显著增加。我们进一步发现，在伸展的肌管中积累了约67 kDa的蛋白质。根据抗原性、大小和pI，我们将该蛋白鉴定为白蛋白，白蛋白与培养基中的白蛋白相同，此外，在伸展的肌管中也检测到添加到培养液中的生物素化白蛋白。因此，我们得出结论，培养液中的白蛋白以一种拉伸依赖的方式被掺入肌管中。牵张依赖的白蛋白摄取的生理学意义仍有待进一步研究。较少

1.With an aim to clarify the effects of mechanical stress on cells in an in vitro system, we manufactured a culture system which permits unidirectional stretch of a cell culture substrate repeatedly over long periods. Thin elastic silicon membrane with fine parallel grooves as a substrate for cell culture and an appropriate culture medium were also devised.2.Since muscle cells are formed and maintained under a mechanically active environment, the effects of mechanical stress on cultured cells were examined with muscle cells as a model and observed two remarkable phenomena caused by stretching : 1) stretch-dependent cell arrangement and 2) hypertrophy of the muscle cells as follows :1) When rat aortic smooth muscle cells (A10) and mouse C2 myoblasts were cultured under a standard condition and then the substrate was stretched repetitively at a frequency of 1 Hz with an amplitude of 20%, the cells became oriented at an angle of about 70o to the direction of stretching. Actin filaments al … More so oriented in the same direction, but filament orientation preceded cell orientation. We found that this stretch-dependent cell orientation was completely blocked by 100 mM gadolinium, an inhibitor of a stretch-activated ion channel, and cycloheximide, but filament reorientation was not affected by these agents at all. From these results, it is concluded that orientation of filaments and the orientation of the cells are closely related but regulated differently.2) In the case of muscle cells (myotubes), stretching in a longitudinal cell axis is important from a physiological view point. Since rearrangement of cell orientation did not occur during stretching of myotubes aligned along the grooves, it was possible to stretch myotubes for more than a week in the direction of the longitudinal cell axis. We observed that myotube diameters increased significantly as compared with the control myotubes cultured without stretch. We further found that a protein of about 67 kDa accumulated in the stretched myotubes. We identified this protein with albumin based on antigenicity, size and pI.The albumin was the same as that in the culture medium and in addition, biotinized albumin added to the medium was also detected in the stretched myotubes. Therefor, we conclude that albumin in the medium was incorporated into myotubes in a stretching-dependent manner. Physiological implication of stretch-dependent albumin uptake remains for future investigation. Less