Journal of Veterinary Science

The Korean Society of Veterinary Science (대한수의학회)
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Interspecies comparative morphological evaluation of the corneal epithelial stem cell niche: a pilot observational study

  • Popova, Petya (Department of Eye and Vision Science, University of Liverpool) ;
  • Malalana, Fernando (Institute of Veterinary Science, University of Liverpool) ;
  • Biddolph, Simon (National Specialist Ophthalmic Pathology Service, Royal Liverpool University Hospital) ;
  • Ramos, Tiago (Department of Eye and Vision Science, University of Liverpool) ;
  • Parekh, Mohit (Institute of Ophthalmology, University College London) ;
  • Chantrey, Julian (Institute of Veterinary Science, University of Liverpool) ;
  • Ahmad, Sajjad (Department of Eye and Vision Science, University of Liverpool)
  • Received : 2022.01.10
  • Accepted : 2022.04.15
  • Published : 2022.07.31
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Abstract

Background: The corneal and limbal morphology relevant to corneal epithelial maintenance in ten different species was examined using histological methods. Objectives: 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. Methods: Corneal sections (4 ㎛) 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. Results: 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. Conclusions: 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.

Keywords

Acknowledgement

The authors thank Jaini Parekh for the illustration of Fig. 1.

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