Structure-Function Relations and Rigidity Percolation in the Shear Properties of Articular Cartilage
Structure-Function Relations and Rigidity Percolation in the Shear Properties of Articular Cartilage
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DOI：
10.1016/j.bpj.2014.08.011
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发表时间：
2014-10-07
影响因子：
3.4
通讯作者：
Cohen, Itai
中科院分区：
文献类型：
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作者：
Silverberg, Jesse L.;Barrett, Aliyah R.;Cohen, Itai
在哺乳动物的软组织中，关节软骨是特别令人感兴趣的，因为它可以承受一生的日常机械负荷，尽管具有最小的再生能力。这种显著的弹性可能是由于深度相关的机械性能，这已被证明是本地化的应变和能量耗散。这种模式提出，这些属性产生的深度依赖性胶原纤维的方向。然而，这种结构-功能关系尚未被量化。在这里，我们使用共聚焦弹性成像，定量偏振光显微镜，傅立叶变换红外成像，使相同的样品测量的深度依赖性剪切模量，胶原纤维组织，和细胞外基质浓度在新生牛关节软骨。我们发现剪切模量垂直酒吧G* 垂直酒吧和胶原纤维的取向和偏振之间的弱相关性。我们发现垂直柱G* 垂直柱和胶原纤维浓度之间有更强的相关性。有趣的是，胶原体积分数v（c）的非常小的变化导致模量的数量级变化，垂直条G* 垂直条缩放为（v（c）- v（0））（xi）。这种依赖性在其他生物聚合物网络的流变学中观察到，其结构表现出刚性渗流相变。沿着这些线，我们提出，在关节软骨中的胶原网络是渗透阈值附近，引起这些大的机械变化和应变在组织的表面的本地化。
Among mammalian soft tissues, articular cartilage is particularly interesting because it can endure a lifetime of daily mechanical loading despite having minimal regenerative capacity. This remarkable resilience may be due to the depth-dependent mechanical properties, which have been shown to localize strain and energy dissipation. This paradigm proposes that these properties arise from the depth-dependent collagen fiber orientation. Nevertheless, this structure-function relationship has not yet been quantified. Here, we use confocal elastography, quantitative polarized light microscopy, and Fourier-transform infrared imaging to make same-sample measurements of the depth-dependent shear modulus, collagen fiber organization, and extracellular matrix concentration in neonatal bovine articular cartilage. We find weak correlations between the shear modulus vertical bar G*vertical bar and both the collagen fiber orientation and polarization. We find a much stronger correlation between vertical bar G*vertical bar and the concentration of collagen fibers. Interestingly, very small changes in collagen volume fraction v(c) lead to orders-of-magnitude changes in the modulus with vertical bar G*vertical bar scaling as (v(c) - v(0))(xi). Such dependencies are observed in the rheology of other biopolymer networks whose structure exhibits rigidity percolation phase transitions. Along these lines, we propose that the collagen network in articular cartilage is near a percolation threshold that gives rise to these large mechanical variations and localization of strain at the tissue's surface.