Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA.
Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA.
J Mech Behav Biomed Mater. 2018 Feb;78:65-73. doi: 10.1016/j.jmbbm.2017.11.001. Epub 2017 Nov 13.
Intracellular network deformation of the cell plays an important role in cellular shape formation. Recent studies suggest that cell reshaping and deformation due to external forces involve cellular volume, pore size, elasticity, and intracellular filaments polymerization degree change. This cell behavior can be described by poroelastic models due to the porous structure of the cytoplasm. In this study, the nanoscale poroelasticity of human mammary basal/claudin low carcinoma cell (MDA-MB-231) was investigated using indentation-based atomic force microscopy. The effects of cell deformation (i.e., indentation) velocity and depth on the poroelasticity of MDA-MB-231 cells were studied. Specifically, the cell poroelastic behavior (i.e., the diffusion coefficient) was quantified at different indenting velocities (0.2, 2, 10, 20, 100, 200 μm/s) and indentation depths (635, 965, and 1313nm) by fitting the force-relaxation curves using a poroelastic model. Cell treated with cytoskeleton inhibitors (latrunculin B, blebbistatin, and nocodazole) were measured to investigate the effect of the cytoskeletal components on the cell poroelasticity. It was found that in general the MDA-MB-231 cells behaved less poroelastic (i.e., with lower diffusion coefficient) at higher indenting velocities due to the local stiffening up and dramatic pore size reduction caused by faster force load, and the cytoplasm is nonlinear in terms of poroelasticity. The poroelastic relaxation was more pronounced when the local cytoplasm porous structure was stretched by higher indentation. Furthermore, inhibition of cytoskeletal components resulted in pronounced poroelastic relaxation when compared with the control, and affected the nonlinearity of cell poroelasticity at different depth range inside of the cell. The comparison between the diffusion coefficient variation and the Young's modulus change under each indentation/treatment condition suggested that the cytoplasm porous geometry is more dominant than the cell Young's modulus in terms of affecting cell poroelasticity.
细胞内网络的变形在细胞形态形成中起着重要作用。最近的研究表明，由于外力导致的细胞重塑和变形涉及细胞体积、孔径大小、弹性和细胞内细丝聚合度的变化。由于细胞质的多孔结构，这种细胞行为可以用多孔弹性模型来描述。在这项研究中，使用基于压痕的原子力显微镜研究了人乳腺基底/闭合蛋白低癌细胞（MDA-MB-231）的纳米级多孔弹性。研究了细胞变形（即压痕）速度和深度对 MDA-MB-231 细胞多孔弹性的影响。具体来说，通过在不同压痕速度（0.2、2、10、20、100、200μm/s）和压痕深度（635、965 和 1313nm）下拟合力松弛曲线，定量了细胞多孔弹性行为（即扩散系数）使用多孔弹性模型。测量了用细胞骨架抑制剂（拉罗丁 B、blebbistatin 和 nocodazole）处理的细胞，以研究细胞骨架成分对细胞多孔弹性的影响。结果发现，一般来说，由于更快的力加载导致局部变硬和孔径急剧减小，较高的压痕速度会导致 MDA-MB-231 细胞表现出较小的多孔弹性（即较低的扩散系数），并且细胞质在多孔弹性方面是非线性的。当局部细胞质多孔结构受到更高的压痕拉伸时，多孔弹性松弛更为明显。此外，与对照相比，抑制细胞骨架成分会导致明显的多孔弹性松弛，并在细胞内部不同深度范围内影响细胞多孔弹性的非线性。在每种压痕/处理条件下，扩散系数变化与杨氏模量变化的比较表明，在影响细胞多孔弹性方面，细胞质多孔几何形状比细胞杨氏模量更为重要。
