Abstract
Purpose: :
To evaluate the effects of desiccating stress on corneal epithelial permeability, smoothness and expression of the tight junction (TJ) complex and the cornified cell envelope (CE) proteins.
Methods: :
Experimental dry eye (EDE) was created in two strains of mice, BALB/c and C57BL/6. Corneal permeability to Oregon green dextran (OGD) was measured. Corneal smoothness was evaluated by graded regularity of a ring reflected off the corneal surface. Ultrastructure was studied by transmission electron microscopy. Real time PCR was performed using Taqman Probes to evaluate expression of CE components (involucrin, small proline–rich (sprr) 1a, 1b, 2a, 2b, 2f, and 2g) and cross–linking transglutaminase enzymes (tgm–1 and 2) by the corneal epithelium. Immunofluorescent staining and laser scanning confocal microscopy was performed to evaluate TJ proteins (occludin and ZO–1), and CE components (involucrin, sprr–1a and sprr–2) on corneal tissue sections and in whole mount corneas.
Results: :
EDE increased corneal permeability to OGD, corneal irregularity and decreased the number of corneal epithelial layers in both strains of mice, but to a greater degree in C57BL/6 mice. EDE increased mRNA involucrin, sprr–1a, 1b, –2a, –2b, –2f, and –2g and protein, tgm–1 and –2 mRNA, and occludin and ZO–1 protein expression in both strains of mice.
Conclusions: :
EDE caused the disruption of the corneal barrier increasing OGD permeability, corneal irregularity, epithelial cell loss and altering expression of TJ and CE proteins, all of which were more severe in C57BL/6 than in BALB/c mice.
Keywords: cornea: tears/tear film/dry eye • cell adhesions/cell junctions • inflammation