Tesson Benoit, Latz Michael I
Scripps Institution of Oceanography, University of California San Diego, La Jolla, California.
Biophys J. 2015 Mar 24;108(6):1341-1351. doi: 10.1016/j.bpj.2015.02.009.
Cells are sophisticated integrators of mechanical stimuli that lead to physiological, biochemical, and genetic responses. The bioluminescence of dinoflagellates, alveolate protists that use light emission for predator defense, serves as a rapid noninvasive whole-cell reporter of mechanosensitivity. In this study, we used atomic force microscopy (AFM) to explore the relationship between cell mechanical properties and mechanosensitivity in live cells of the dinoflagellate Pyrocystis lunula. Cell stiffness was 0.56 MPa, consistent with cells possessing a cell wall. Cell response depended on both the magnitude and velocity of the applied force. At the maximum stimulation velocity of 390 μm s(-1), the threshold response occurred at a force of 7.2 μN, resulting in a contact time of 6.1 ms and indentation of 2.1 μm. Cells did not respond to a low stimulation velocity of 20 μm s(-1), indicating a velocity dependent response that, based on stress relaxation experiments, was explained by the cell viscoelastic properties. This study demonstrates the use of AFM to study mechanosensitivity in a cell system that responds at fast timescales, and provides insights into how viscoelastic properties affect mechanosensitivity. It also provides a comparison with previous studies using hydrodynamic stimulation, showing the discrepancy in cell response between direct compressive forces using AFM and those within flow fields based on average flow properties.
细胞是机械刺激的精密整合者，会引发生理、生化和基因反应。腰鞭毛虫是一类利用发光进行捕食者防御的肺泡状原生生物，其生物发光可作为一种快速、非侵入性的细胞机械敏感性全细胞报告物。在本研究中，我们使用原子力显微镜（AFM）来探究腰鞭毛虫新月扁藻活细胞的细胞机械特性与机械敏感性之间的关系。细胞硬度为0.56兆帕，这与具有细胞壁的细胞一致。细胞反应取决于所施加力的大小和速度。在390微米/秒的最大刺激速度下，阈值反应出现在7.2微牛的力时，导致接触时间为6.1毫秒，压痕为2.1微米。细胞对20微米/秒的低刺激速度没有反应，这表明基于应力松弛实验，细胞反应具有速度依赖性，这是由细胞粘弹性特性所解释的。本研究展示了使用AFM来研究在快速时间尺度上做出反应的细胞系统中的机械敏感性，并深入了解粘弹性特性如何影响机械敏感性。它还与之前使用流体动力学刺激的研究进行了比较，显示了使用AFM的直接压缩力与基于平均流动特性的流场内的力之间细胞反应的差异。
