Mechanical interactions between collagen and proteoglycans: implications for the stability of lung tissue
Mechanical interactions between collagen and proteoglycans: implications for the stability of lung tissue
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DOI：
10.1152/japplphysiol.00619.2004
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发表时间：
2005-02-01
影响因子：
3.3
通讯作者：
Suki, B
中科院分区：
文献类型：
--
作者：
Cavalcante, FSA;Ito, S;Suki, B
胶原蛋白和弹性蛋白被认为支配着包括肺实质在内的结缔组织的弹性。蛋白聚糖上的糖胺聚糖也可能发挥作用，因为间质液的渗透压可以改变带负电荷的糖胺聚糖上的排斥力，使它们塌陷或膨胀，这可以影响纤维的拉伸和折叠模式。因此，我们假设肺组织的弹性主要来自1）胶原蛋白-弹性蛋白网络的拓扑结构和2）蛋白聚糖和纤维之间的机械相互作用。我们测量了肺组织片在低渗、正常和高渗溶液中的准静态、单轴应力-应变曲线。我们发现，应力-应变曲线是敏感的渗透压，但这种敏感性下降后，蛋白多糖消化。免疫荧光标记的胶原网络图像显示，纤维沿着肺泡壁形成六边形结构。尽管大的异质性，在30%的单轴应变的六边形的纵横比与渗透压线性增加。我们开发了一个二维六边形网络模型的肺泡结构，将胶原弹性蛋白纤维的机械性能和它们与蛋白多糖的相互作用。该模型占在所有实验条件下观察到的应力-应变曲线。该模型还预测了纵横比如何随渗透压和应变而变化，这使我们能够估计单个肺泡壁和胶原纤维的杨氏模量。因此，我们确定了一个新的和重要的作用，蛋白聚糖：他们稳定的胶原蛋白弹性蛋白网络的结缔组织，并有助于肺弹性和肺泡稳定性在低至中等肺容量。
Collagen and elastin are thought to dominate the elasticity of the connective tissue including lung parenchyma. The glycosaminoglycans on the proteoglycans may also play a role because osmolarity of interstitial fluid can alter the repulsive forces on the negatively charged glycosaminoglycans, allowing them to collapse or inflate, which can affect the stretching and folding pattern of the fibers. Hence, we hypothesized that the elasticity of lung tissue arises primarily from 1) the topology of the collagen-elastin network and 2) the mechanical interaction between proteoglycans and fibers. We measured the quasi-static, uniaxial stress-strain curves of lung tissue sheets in hypotonic, normal, and hypertonic solutions. We found that the stress-strain curve was sensitive to osmolarity, but this sensitivity decreased after proteoglycan digestion. Images of immunofluorescently labeled collagen networks showed that the fibers follow the alveolar walls that form a hexagonal-like structure. Despite the large heterogeneity, the aspect ratio of the hexagons at 30% uniaxial strain increased linearly with osmolarity. We developed a two-dimensional hexagonal network model of the alveolar structure incorporating the mechanical properties of the collagen-elastin fibers and their interaction with proteoglycans. The model accounted for the stress-strain curves observed under all experimental conditions. The model also predicted how aspect ratio changed with osmolarity and strain, which allowed us to estimate the Young's modulus of a single alveolar wall and a collagen fiber. We therefore identify a novel and important role for the proteoglycans: they stabilize the collagen-elastin network of connective tissues and contribute to lung elasticity and alveolar stability at low to medium lung volumes.