Department of Chemical and Materials Engineering, University of Auckland, Auckland, New Zealand.
Orthopaedic Biomechanics Group, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
J Anat. 2022 Jan;240(1):107-119. doi: 10.1111/joa.13527. Epub 2021 Aug 1.
This multi-length scale anatomical study explores the influence of mild cartilage structural degeneration on the tissue swelling response. While the swelling response of cartilage has been studied extensively, this is the first study to reveal and correlate tissue microstructure and ultrastructure, with the swelling induced cartilage tissue strains. Cartilage sample strips (n = 30) were obtained from the distal-lateral quadrant of thirty mildly degenerate bovine patellae and, following excision from the bone, the cartilage strips were allowed to swell freely for 2 h in solutions of physiological saline and distilled water successively. The swelling response of this group of samples were compared with that of healthy cartilage, with (n = 20) and without the surface layer (n = 20). The subsequent curling response of cartilage showed that in healthy tissue it was highly variable, and with the surface removed some samples curved in the opposite direction, while in the mildly degenerate tissue group, virtually all tissue strips curved in a consistent upward manner. A significant difference in strain was observed between healthy samples with surface layer removed and mildly degenerate samples, illustrating how excision of the surface zone from pristine cartilage is insufficient to model the swelling response of tissue which has undergone natural degenerative changes. On average, total tissue thickness increased from 940 µm (healthy) to 1079 µm (mildly degenerate), however, looking at the zonal strata, surface and transition zone thicknesses both decreased while deep zone thickness increased from healthy to mildly degenerate tissue. Morphologically, changes to the surface zone integrity were correlated with a diminished surface layer which, at the ultrastructural scale, correlated with a decreased fibrillar density. Similarly, fibrosity of the general matrix visible at the microscale was associated with a loss of later interconnectivity resulting in large, aggregated fibril bundles. The microstructural and ultrastructural investigation revealed that the key differences influencing the tissue swelling strain response was (1) the thickness and extent of disruption to the surface layer and (2) the amount of fibrillar network destructuring, highlighting the importance of the collagen and tissue matrix structure in restraining cartilage swelling.
这项多长度尺度解剖学研究探讨了轻度软骨结构退变对组织肿胀反应的影响。尽管软骨的肿胀反应已被广泛研究，但这是第一项揭示和关联组织微观结构和超微结构与诱导软骨组织应变的肿胀反应的研究。从三十个轻度退变的牛髌骨的远端外侧象限获得软骨样本条（n=30），并从骨上切除后，软骨条在生理盐溶液和蒸馏水的溶液中自由膨胀 2 小时。将这组样本的肿胀反应与健康软骨（n=20）和无表面层（n=20）的肿胀反应进行比较。软骨的后续卷曲反应表明，在健康组织中，其变化很大，而去除表面层后，一些样本向相反方向卷曲，而在轻度退变组织组中，几乎所有组织条都以一致的向上方式卷曲。观察到有和无表面层的健康样本之间存在明显的应变差异，这说明了从原始软骨中切除表面区域不足以模拟已经经历自然退行性变化的组织的肿胀反应。平均而言，总组织厚度从健康样本的 940µm（健康）增加到 1079µm（轻度退变），然而，观察到区带层，表面和过渡层的厚度均减少，而深层区带的厚度从健康组织增加到轻度退变组织。形态上，表面层完整性的变化与表面层的减少有关，在超微结构尺度上，与纤维密度的降低有关。同样，在微观尺度上可见的基质一般纤维状的变化与后期互连成纤维束的损失有关，导致大的、聚集的纤维束。微观结构和超微结构研究表明，影响组织肿胀应变反应的关键差异是（1）表面层的厚度和破坏程度，（2）纤维网络解构的程度，突出了胶原和组织基质结构在抑制软骨肿胀中的重要性。
