Anti–Inflammatory Therapy Preserves Corneal Barrier Function in Experimental Murine Dry Eye

Abstract

Abstract: : Purpose: To investigate the effects of anti–inflammatory therapy on tight junction (TJ) protein expression and barrier function of corneal epithelia in experimental murine dry eye. Methods: C57BL6 mice aged 6–8 weeks were treated with systemic scopolamine and exposure to an air draft for 5 days to induce experimental dry eye (EDE), with or without topical therapy, 1% methylprednisolone, 0.025% doxycycline or balanced salt solution (BSS) 4 times per day. Untreated (UT) mice were used as controls. The expression of involucrin, zonula occludens (ZO–1) and occludin were evaluated by laser scanning confocal microscopy (whole mount corneas) and immunofluorescent staining (tissue sections). Epithelial proliferation was evaluated by BrdU incorporation. Oregon green dextran (OGD, 70kDa) was used to measure corneal permeability. Results:EDE significantly increased expression of involucrin, compared to UT and treatment groups. EDE also induced marked changes in occludin and ZO–1 expression, with increased cytoplasmic and decreased membrane staining in apical cells of the corneal epithelia. Extensive desquamation of apical cells was observed in the EDE group. Corneal permeability to OGD increased in EDE, with punctate and confluent dye staining, mimicking human corneal disease. BrdU incorporation increased in corneal epithelial cells of EDE. Treatment of EDE with methylprednisolone or doxycycline preserved the TJ network, decreased expression of involucrin, reduced BrdU incorporation and corneal permeability to OGD, indicating preserved corneal barrier function. BSS treatment showed no protective effect, with TJ expression, BrdU incorporation and corneal permeability similar to EDE. Conclusions: EDE causes altered expression of TJ proteins in the corneal epithelium that is accompanied by increased expression of a cornified envelope protein, involucrin. Treatment of EDE with methylprednisolone or doxycycline preserved corneal barrier function.

Keywords: cornea: tears/tear film/dry eye • cell adhesions/cell junctions • microscopy: confocal/tunneling