Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA.
Laboratoire Interdisciplinaire de Physique (LIPhy), Université Grenoble Alpes and CNRS, F-38000 Grenoble, France.
Soft Matter. 2024 Jul 31;20(30):6033-6043. doi: 10.1039/d4sm00617h.
Proteoglycans are hierarchically organized structures that play an important role in the hydration and the compression resistance of cartilage matrix. In this study, the static and dynamic properties relevant to the biomechanical function of cartilage are determined at different levels of the hierarchical structure, using complementary osmotic pressure, neutron scattering (SANS) and light scattering (DLS) measurements. In cartilage proteoglycans (PGs), two levels of bottlebrush structures can be distinguished: the aggrecan monomer, which consists of a core protein to which are tethered charged glycosaminoglycan (GAG) chains, and complexes formed of the aggrecan monomers attached around a linear hyaluronic acid backbone. The principal component of GAG, chondroitin sulfate (CS), is used as a baseline in this comparison. The osmotic modulus, measured as a function of the proteoglycan concentration, follows the order CS < aggrecan < aggrecan-HA complex. This order underlines the benefit of the increasing complexity at each level of the molecular architecture. The hierarchical bottlebrush configuration, which prevents interpenetration among the bristles of the aggrecan monomers, enhances both the mechanical properties and the osmotic resistance. The osmotic pressure of the collagen solution is notably smaller than in the proteoglycan systems. This is consistent with its known primary role to provide tensile strength to the cartilage and to confine the aggrecan-HA complexes, as opposed to load bearing. The collective diffusion coefficient governs the rate of recovery of biological tissue after compressive load. In CS solutions the diffusion process is fast, ≈ 3 × 10 cm s at concentrations comparable with that of the GAG chains inside the aggrecan molecule. In CS solutions is a weakly decreasing function of calcium ion concentration, while in aggrecan and its complexes with HA, the relaxation rate is insensitive to the presence of calcium.
蛋白聚糖是具有层次结构的组织，在软骨基质的水合和抗压阻力中发挥重要作用。在这项研究中，使用渗透压、中子散射（SANS）和光散射（DLS）测量法，在不同层次结构水平上测定与软骨生物力学功能相关的静态和动态特性。在软骨蛋白聚糖（PG）中，可以区分两种层次的瓶刷结构：核心蛋白连接带电荷糖胺聚糖（GAG）链的聚集蛋白聚糖单体，以及通过连接在线性透明质酸主链周围的聚集蛋白聚糖单体形成的复合物。GAG 的主要成分硫酸软骨素（CS）在这种比较中用作基线。作为蛋白聚糖浓度函数测量的渗透压模量遵循 CS <聚集蛋白聚糖<聚集蛋白聚糖-HA 复合物的顺序。这种顺序强调了分子结构中每个层次增加复杂性的好处。防止聚集蛋白聚糖单体的刷毛相互渗透的分层瓶刷结构，增强了机械性能和渗透压阻力。胶原溶液的渗透压明显小于蛋白聚糖系统。这与其作为软骨的拉伸强度提供者和聚集蛋白聚糖-HA 复合物的限制者的已知主要作用是一致的，而不是承重者。集体扩散系数 控制生物组织在压缩载荷后恢复的速率。在 CS 溶液中，扩散过程很快，在与聚集蛋白聚糖分子内 GAG 链浓度相当的浓度下， ≈ 3 × 10 cm s。在 CS 溶液中，是钙离子浓度的弱递减函数，而在聚集蛋白聚糖及其与 HA 的复合物中，弛豫速率对钙离子的存在不敏感。
