Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA.
Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA.
Exp Eye Res. 2023 Jun;231:109476. doi: 10.1016/j.exer.2023.109476. Epub 2023 Apr 15.
The mechanical and physical properties of the cornea originate from the microstructure and composition of its extracellular matrix. It is known that collagen fibrils, with a relatively uniform diameter, are organized in a pseudo-hexagonal array. It has been suggested that proteoglycans and the interaction of their glycosaminoglycan (GAG) side chains with themselves and collagen fibrils are important for collagen fibril organization inside the cornea. There are several diseases such as keratoconus in which the regular collagen fibrillar packing becomes distorted causing corneal optical and mechanical properties to be compromised. The primary purpose of the present work was to investigate the role of GAGs on the microstructure of corneal extracellular matrix before and after corneal crosslinking (CXL) treatment. For this purpose, keratan sulphates (KS) were removed from corneal samples using the keratanase enzyme and the CXL procedure was used to crosslink the specimens. The transmission electron microscopy was then used to characterize the diameter of collagen fibrils and their interfibrillar spacing. It was found that KS GAG depletion increased the collagen interfibrillar spacing while the CXL treatment significantly decreased the interfibrillar spacing. The enzyme and CXL treatments had an insignificant effect on the diameter of collagen fibrils. The underlying mechanisms responsible for these observations were discussed in terms of the assumption that GAG chains form duplexes that behave as tiny ropes holding collagen fibrils in place.
角膜的机械和物理性能源于其细胞外基质的微观结构和组成。众所周知，具有相对均匀直径的胶原纤维原纤维以拟六方阵列的形式排列。有人认为，蛋白聚糖及其糖胺聚糖 (GAG) 侧链与自身和胶原纤维原纤维的相互作用对于角膜内胶原纤维原纤维的组织排列很重要。有几种疾病，如圆锥角膜，其中规则的胶原纤维原纤维包装变得扭曲，导致角膜光学和机械性能受损。目前这项工作的主要目的是研究 GAG 在前角膜交联 (CXL) 治疗前后对角膜细胞外基质微观结构的作用。为此，使用角蛋白酶从角膜样本中去除硫酸软骨素 (KS)，并使用 CXL 程序对标本进行交联。然后使用透射电子显微镜来表征胶原纤维原纤维的直径及其纤维间间距。结果发现，KS GAG 耗尽增加了胶原纤维间的间距，而 CXL 处理显著降低了纤维间的间距。酶和 CXL 处理对胶原纤维原纤维的直径没有显著影响。根据假设 GAG 链形成双螺旋，这些观察结果的潜在机制被讨论，双螺旋的行为就像细小的绳索一样将胶原纤维原纤维固定在适当的位置。
