Win Zaw, Buksa Justin M, Steucke Kerianne E, Gant Luxton G W, Barocas Victor H, Alford Patrick W
Department of Biomedical Engineering, University of Minnesota-Twin Cities, 312 Church Street SE NHH 7-105, Minneapolis, MN 55455 e-mail:
Department of Genetics, Cell Biology, and Development, University of Minnesota-Twin Cities, 420 Washington Avenue SE MCB 4-128, Minneapolis, MN 55455 e-mail:
J Biomech Eng. 2017 Jul 1;139(7):0710061-07100610. doi: 10.1115/1.4036440.
The stress in a cell due to extracellular mechanical stimulus is determined by its mechanical properties, and the structural organization of many adherent cells suggests that their properties are anisotropic. This anisotropy may significantly influence the cells' mechanotransductive response to complex loads, and has important implications for development of accurate models of tissue biomechanics. Standard methods for measuring cellular mechanics report linear moduli that cannot capture large-deformation anisotropic properties, which in a continuum mechanics framework are best described by a strain energy density function (SED). In tissues, the SED is most robustly measured using biaxial testing. Here, we describe a cellular microbiaxial stretching (CμBS) method that modifies this tissue-scale approach to measure the anisotropic elastic behavior of individual vascular smooth muscle cells (VSMCs) with nativelike cytoarchitecture. Using CμBS, we reveal that VSMCs are highly anisotropic under large deformations. We then characterize a Holzapfel-Gasser-Ogden type SED for individual VSMCs and find that architecture-dependent properties of the cells can be robustly described using a formulation solely based on the organization of their actin cytoskeleton. These results suggest that cellular anisotropy should be considered when developing biomechanical models, and could play an important role in cellular mechano-adaptation.
细胞因细胞外机械刺激而产生的应力取决于其力学特性，许多贴壁细胞的结构组织表明它们的特性是各向异性的。这种各向异性可能会显著影响细胞对复杂载荷的机械转导反应，并对准确的组织生物力学模型的开发具有重要意义。测量细胞力学的标准方法报告的线性模量无法捕捉大变形各向异性特性，在连续介质力学框架中，这些特性最好用应变能密度函数（SED）来描述。在组织中，使用双轴测试可以最可靠地测量SED。在这里，我们描述了一种细胞微双轴拉伸（CμBS）方法，该方法改进了这种组织尺度的方法，以测量具有天然细胞结构的单个血管平滑肌细胞（VSMC）的各向异性弹性行为。使用CμBS，我们发现VSMC在大变形下具有高度各向异性。然后，我们为单个VSMC表征了一种Holzapfel-Gasser-Ogden型SED，并发现可以使用仅基于其肌动蛋白细胞骨架组织的公式来可靠地描述细胞的结构依赖性特性。这些结果表明，在开发生物力学模型时应考虑细胞各向异性，并且它可能在细胞机械适应中发挥重要作用。
