Guilak F, Mow V C
Orthopaedic Research Laboratories, Departments of Surgery, Biomedical Engineering, and Mechanical Engineering & Materials Science, Duke University Medical Center, P.O. Box 3093, 375 MSRB, 27710, Durham, NC, USA.
J Biomech. 2000 Dec;33(12):1663-73.
Mechanical compression of the cartilage extracellular matrix has a significant effect on the metabolic activity of the chondrocytes. However, the relationship between the stress-strain and fluid-flow fields at the macroscopic "tissue" level and those at the microscopic "cellular" level are not fully understood. Based on the existing experimental data on the deformation behavior and biomechanical properties of articular cartilage and chondrocytes, a multi-scale biphasic finite element model was developed of the chondrocyte as a spheroidal inclusion embedded within the extracellular matrix of a cartilage explant. The mechanical environment at the cellular level was found to be time-varying and inhomogeneous, and the large difference ( approximately 3 orders of magnitude) in the elastic properties of the chondrocyte and those of the extracellular matrix results in stress concentrations at the cell-matrix border and a nearly two-fold increase in strain and dilatation (volume change) at the cellular level, as compared to the macroscopic level. The presence of a narrow "pericellular matrix" with different properties than that of the chondrocyte or extracellular matrix significantly altered the principal stress and strain magnitudes within the chondrocyte, suggesting a functional biomechanical role for the pericellular matrix. These findings suggest that even under simple compressive loading conditions, chondrocytes are subjected to a complex local mechanical environment consisting of tension, compression, shear, and fluid pressure. Knowledge of the local stress and strain fields in the extracellular matrix is an important step in the interpretation of studies of mechanical signal transduction in cartilage explant culture models.
软骨细胞外基质的机械压缩对软骨细胞的代谢活性有显著影响。然而，宏观“组织”水平和微观“细胞”水平上的应力应变场与流体流动场之间的关系尚未完全明确。基于现有关节软骨和软骨细胞变形行为及生物力学特性的实验数据，建立了一个多尺度双相有限元模型，该模型将软骨细胞视为嵌入软骨外植体胞外基质中的球状内含物。研究发现细胞水平的力学环境随时间变化且不均匀，软骨细胞与胞外基质弹性特性的巨大差异（约3个数量级）导致细胞 - 基质边界处出现应力集中，与宏观水平相比，细胞水平的应变和膨胀（体积变化）增加近两倍。具有与软骨细胞或胞外基质不同特性的狭窄“细胞周基质”的存在显著改变了软骨细胞内的主应力和应变大小，表明细胞周基质具有功能性生物力学作用。这些发现表明，即使在简单的压缩加载条件下，软骨细胞也会受到由拉伸、压缩、剪切和流体压力组成的复杂局部力学环境的影响。了解胞外基质中的局部应力和应变场是解释软骨外植体培养模型中机械信号转导研究的重要一步。
