Department of Eye and Vision Science, University of Liverpool, Liverpool L7 8TX, UK.
Institute of Veterinary Science, University of Liverpool, Liverpool L3 5RF, UK.
J Vet Sci. 2022 Jul;23(4):e62. doi: 10.4142/jvs.22009.
The corneal and limbal morphology relevant to corneal epithelial maintenance in ten different species was examined using histological methods.
The presence of a Bowman's layer, limbal epithelial cell, and superficial stromal morphology was examined in the following species to evaluate the differences in corneal thickness and epithelium: Java sparrows, frogs, macaws, spoonbills, red pandas, penguins, horses, Dobermans, orangutans, and humans.
Corneal sections (4 µm) were obtained from ten ocular globes from three different animal classes: Aves, Amphibia, and Mammalia. All sections were stained with hematoxylin and eosin and periodic acid-Schiff reaction. After microscopy, all stained slides were photographed and analyzed.
Significant morphological differences in the corneal and limbal epithelia and their underlying stroma between species were observed. The number of corneal epithelial cell layers and the overall corneal epithelial thickness varied significantly among the species. The presence of a Bowman's layer was only observed in primates (orangutans and humans). Presumed supranuclear melanin caps were noted in four species (orangutans, macaws, red pandas, and horses) in the limbal basal epithelial layer (putative site of corneal epithelial stem cells). The melanin granules covered the apex of the cell nucleus.
Supranuclear melanin capping has been described as a process within the epidermis to reduce the concentration of ultraviolet-induced DNA photoproducts. Similarly, there may be a relationship between limbal stem cell melanin capping as a protective mechanism against ultra-violet radiation.
使用组织学方法检查了十种不同物种与角膜上皮维持相关的角膜和缘部形态。
检查以下物种的 Bowman 层、缘部上皮细胞和浅层基质形态的存在，以评估角膜厚度和上皮的差异：Java 麻雀、青蛙、金刚鹦鹉、琵鹭、红熊猫、企鹅、马、杜宾犬、猩猩和人类。
从三个不同动物类别的十个眼部球体中获得 4 µm 的角膜切片：鸟类、两栖类和哺乳类。所有切片均用苏木精和伊红以及过碘酸-Schiff 反应染色。显微镜检查后，所有染色的载玻片均拍照并进行分析。
观察到物种间角膜和缘部上皮及其下基质的显著形态差异。角膜上皮细胞层的数量和整个角膜上皮的厚度在物种间差异显著。Bowman 层仅在灵长类动物（猩猩和人类）中存在。在缘部基底上皮层（推测为角膜上皮干细胞的部位）中，四个物种（猩猩、金刚鹦鹉、红熊猫和马）中存在假定的核上黑色素帽。黑色素颗粒覆盖了细胞核的顶端。
核上黑色素帽化已被描述为表皮内的一个过程，以减少紫外线诱导的 DNA 光产物的浓度。同样，缘部干细胞黑色素帽化可能与紫外线辐射的保护机制有关。
