Measurement of mechanical properties of cells based on their internal structures

细胞的力学特性与细胞骨架的关系在机械转导中具有重要意义。在这项研究中，我们主要用微拉伸测试仪测量了从主动脉壁新分离的平滑肌细胞（SMCs）和分离后培养的平滑肌细胞（CSMCs）的准静态拉伸特性和应力松弛反应，以了解肌动蛋白丝（AF）或微管（MT）断裂的影响。用细胞旋转系统观察了它们的三维显微结构。得到了以下结果：1。在AF排列的纵向上，FSMCs的刚度增加，AF破坏后CSMCs的刚度下降了60%，表明AF对其拉伸性能起主导作用。CSMCs的应力松弛响应可以用~ 1 min的快速指数衰减和~ 1 h的慢速衰减相结合的方式来表达，AF的破坏导致慢速衰减发生了显著变化。我们建立了一种方法来拉伸细胞，使其在基底上保持形状，并发现在AF和MT破坏后，CSMCs的刚度分别下降了70%和30%。MTs可能在smcs的拉伸性能中起重要作用。我们成功地用细胞旋转系统观察到AFs在FSMCs中呈螺旋排列，并且当细胞与底物分离并收缩时，CSMCs的细胞核屈曲。用原子力显微镜测量的局部刚度在csmc的MT破坏后增加。培养成纤维细胞的全细胞硬度在MT中断后没有改变，但在AF中断后显著降低了约75%。这些结果表明，除了af外，mt对细胞的力学性能也有显著的影响，但mt的贡献程度取决于细胞的类型和变形方式。

Relationship linking mechanical properties of cells and their cytoskeletons are important in mechanotransduction. In this study, we measured quasi-static tensile properties and stress relaxation responses mainly of smooth muscle cells (SMCs) freshly isolated from aortic walls (FSMCs) and those cultured following isolation (CSMCs) with micro tensile testers to know the effects of the disruption of actin filaments (AF) or microtubules (MT). Their 3D microstructures were observed with a cell rotation system. Following results were obtained:1. FSMCs were stiffer in their longitudinal direction in which AFs align, and the stiffness of CSMCs decreased by 60% following AF disruption, indicating that AFs play dominant roles in their tensile properties.2. Stress relaxation response of CSMCs could be expressed with the combination of fast exponential decay with a time constant of〜1 min and slow decay with a time constant of 〜1 h, and the AF disruption caused significant change in the slow decay.3. We established a method to stretch cells maintaining their shape on substrate and found that the stiffness of CSMCs decreased by 70 and 30% following AF and MT disruption, respectively. MTs may play significant roles in the tensile properties of SMCs.4. We successfully observed with the cell rotation system that AFs aligned helically in the FSMCs and that nucleus of CSMCs buckled when the cells were detached from substrate and shrank.5. Local stiffness measured with an atomic force microscope increased following MT disruption in CSMCs. Whole-cell stiffness of cultured fibroblasts did not change following MT disruption, but decreased significantly by〜75% following AF disruption.These results indicate that not only AFs but also MTs have significant effects on cell mechanical properties, but the degree of contribution of MTs depends on the cell types and mode of deformation.