Department of Chemical and Materials Engineering, The University of Auckland, New Zealand; Department of Biomedical Engineering, Eindhoven University of Technology, the Netherlands.
Department of Chemical and Materials Engineering, The University of Auckland, New Zealand.
J Mech Behav Biomed Mater. 2017 Nov;75:390-398. doi: 10.1016/j.jmbbm.2017.07.042. Epub 2017 Aug 3.
The functional coupling between the fibrillar network and the high-swelling proteoglycans largely determines the mechanical properties of the articular cartilage matrix. The objective of this new study was to show specifically how changes in fibrillar interconnectivity arising from early cartilage degeneration influence transverse stiffness and swelling properties at the tissue level.
Radial zone transverse layers of cartilage matrix were obtained from intact and mildly degenerate bovine patellae. Each layer was then subdivided to assess tensile stiffness, free-swelling response, glycosaminoglycan (GAG) content, and micro- and ultra-structural features.
The tensile modulus was significantly lower and the degree of swelling significantly higher for the degenerate matrix compared to the intact. Scanning electron microscopy revealed a homogeneous response to transverse strain in the intact cartilage, whereas large non-fibrillar spaces between fibril aggregates were visible in the degenerate matrix. Although there were no significant differences in GAG content it did correlate significantly with stiffness and swelling in the intact samples but not in the degenerate.
The lower degree of fibril network interconnectivity in the degenerate matrix led to both a decreased transverse stiffness and reduced resistance to osmotic swelling. This network 'de-structuring' also resulted in a reduced functional interaction between the fibrillar network and the proteoglycans. The study provides new insights into the role of the fibrillar network and how changes in the network arising from the degenerative cascade will influence tissue level behaviour.
纤维网络与高膨胀蛋白聚糖之间的功能偶联在很大程度上决定了关节软骨基质的机械性能。本项新研究的目的是专门展示源自早期软骨退变的纤维网络连通性变化如何影响组织水平的横向硬度和膨胀特性。
从完整和轻度退变的牛髌骨中获得了软骨基质的放射状区横向层。然后将每个层细分，以评估拉伸刚度、自由膨胀响应、糖胺聚糖 (GAG) 含量以及微观和超微结构特征。
与完整的相比，退变的基质的拉伸模量显著降低，膨胀程度显著增加。扫描电子显微镜显示完整软骨对横向应变的均匀响应，而退变基质中纤维聚集体之间可见大的无纤维空间。尽管 GAG 含量没有显著差异，但它与完整样本的刚度和膨胀显著相关，但与退变样本无关。
退变基质中纤维网络连通性降低，导致横向刚度降低和对渗透膨胀的抵抗力降低。这种网络“解构”也导致纤维网络与蛋白聚糖之间的功能相互作用减少。该研究深入了解了纤维网络的作用以及退变级联中网络的变化将如何影响组织水平的行为。
