Jaasma Michael J, Jackson Wesley M, Tang Raymond Y, Keaveny Tony M
Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740, USA.
J Biomech. 2007;40(9):1938-45. doi: 10.1016/j.jbiomech.2006.09.010. Epub 2006 Nov 9.
Numerous cellular biochemical responses to mechanical loading are transient, indicating a cell's ability to adapt its behavior to a new mechanical environment. Since load-induced cellular deformation can initiate these biochemical responses, the overall goal of this study was to investigate the adaptation of global, or whole-cell, mechanical behavior, i.e., cellular deformability, in response to mechanical loading for osteoblastic cells. Confluent cell cultures were subjected to 1 or 2 Pa flow-induced shear stress for 2 h. Whole-cell mechanical behavior was then measured for individual cells using an atomic force microscope. Compared to cells maintained under static conditions, whole-cell stiffness was 1.36-fold (p=0.006) and 1.70-fold (p<0.001) greater for cells exposed to 1 and 2 Pa shear loading, respectively. The increase in shear stress magnitude from 1 to 2 Pa also caused a statistically significant, 1.25-fold increase in cell stiffness (p=0.02). Increases in cell stiffness were not altered in either flow group for 70 min after flow was terminated (p=0.15). Flow-induced rearrangement of the actin cytoskeleton was also maintained for at least 90 min after flow was terminated. Taken together, these findings support the hypothesis that cells become mechanically adapted to their mechanical environment via cytoskeletal modifications. Accordingly, cellular mechanical adaptation may play a key role in regulation of cellular mechanosensitivity and the related effects on tissue structure and function.
细胞对机械负荷的众多生化反应是短暂的，这表明细胞有能力使其行为适应新的机械环境。由于负荷诱导的细胞变形可引发这些生化反应，本研究的总体目标是研究成骨细胞在机械负荷作用下整体或全细胞机械行为的适应性，即细胞变形能力。将汇合的细胞培养物置于1或2帕的流动诱导剪切应力下2小时。然后使用原子力显微镜测量单个细胞的全细胞机械行为。与在静态条件下培养的细胞相比，暴露于1帕和2帕剪切负荷的细胞的全细胞刚度分别提高了1.36倍（p = 0.006）和1.70倍（p < 0.001）。剪切应力大小从1帕增加到2帕也导致细胞刚度在统计学上显著增加1.25倍（p = 0.02）。在流动终止后70分钟内，两个流动组的细胞刚度增加均未改变（p = 0.15）。流动诱导的肌动蛋白细胞骨架重排也在流动终止后至少维持90分钟。综上所述，这些发现支持了这样一种假设，即细胞通过细胞骨架修饰在机械上适应其机械环境。因此，细胞机械适应可能在调节细胞机械敏感性以及对组织结构和功能的相关影响中起关键作用。
