title: Comparative morphological evaluation of domestic animal cornea.
abstract: OBJECTIVE
  This study described corneal morphology in different domestic animals using histological and immunohistochemical methods. Specifically, we evaluated the species-specific distribution pattern of cytokeratins (CKs) and aquaporins (AQPs) to assess their contribution to the strength and transparency of the cornea, respectively.
  
  
  METHODS
  Corneal sections (2 μm thick) were obtained from 28 pigs, 11 cows, two goats, six horses, four dogs, and five cats and stained with hematoxylin-eosin and periodic acid-Schiff (PAS) reaction. Immunohistochemistry was also performed using CK1 to 3 and AQP1 and 5 antibodies.
  
  
  RESULTS
  Domestic animal corneas were composed of corneal epithelium, stroma, Descemet's membrane, and corneal endothelium. Bowman's layer was not detected using the PAS reaction. The three-layered epithelium was thinnest in carnivores and thickest in equines and bovines. CKs were demonstrated immunohistochemically in all species examined, especially in the most superficial layer of the corneal epithelium. CKs were more widely distributed in canine and feline corneal epithelial cell layers compared to other species. The corneal monolayer endothelium was immunostained with AQP1 in all species examined, and it was also present in stromal keratocytes in a species-specific manner. In contrast, AQP5 was exclusively localized to the corneal epithelium. Epithelial staining patterns varied markedly between species, and the widest distribution of AQP5 was demonstrated in feline epithelial cell layers.
  
  
  CONCLUSIONS
  Differences in the distribution of CKs and AQPs in various species suggest species differences in the maintenance of structural integrity and fluid balance.
authors.affiliation: Institute of Anatomy and Physiology of Domestic Animals, University of Hohenheim, Fruwirthstr. 35, D-70599, Stuttgart, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Nautscher
authors.affiliation: Institute of Anatomy and Physiology of Domestic Animals, University of Hohenheim, Fruwirthstr. 35, D-70599, Stuttgart, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Bauer
authors.affiliation: Institute of Anatomy and Physiology of Domestic Animals, University of Hohenheim, Fruwirthstr. 35, D-70599, Stuttgart, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Steffl
authors.affiliation: Institute of Anatomy and Physiology of Domestic Animals, University of Hohenheim, Fruwirthstr. 35, D-70599, Stuttgart, Germany.
authors.forename: Werner M
authors.initials: WM
authors.lastname: Amselgruber
mesh_terms: D000818:Animals; D000829:Animals, Domestic / Q000033:anatomy & histology* / Q000145:classification*; D003315:Cornea / Q000033:anatomy & histology*; D013045:Species Specificity
keywords: aquaporins; cornea; cytokeratins; domestic animals; histology; immunohistochemistry