Apical corneal barrier disruption in experimental murine dry eye is abrogated by methylprednisolone and doxycycline

PURPOSE. To evaluate the mechanism of apical corneal epithelial barrier disruption in response to experimental ocular surface desiccation and the effects of two anti-inflammatory agents (methylprednisolone and doxycycline) on this process. METHODS. Experimental dry eye (EDE) was created in C57BL/6 mice, without or with topical therapy, 1% methylprednisolone, 0.025% doxycycline, or physiologic saline solution (PSS) four times per day. Corneal smoothness and Oregon green dextran (OGD) permeability were assessed. Desquamation of and cornified envelope protein (involucrin and small proline-rich protein [SPRR]-2) expression by the corneal epithelium was evaluated by laser scanning confocal microscopy. Levels of cornified envelope proteins mRNA were measured by real-time PCR. RESULTS. Corneal OGD permeability, surface irregularity, and the number of desquamating apical corneal epithelia significantly increased in EDE. Desiccating stress significantly increased expression of involucrin and SPRR-2 in the corneal epithelia. Treatment of EDE with methylprednisolone or doxycycline reduced corneal permeability to OGD, improved corneal smoothness, and decreased involucrin and SPRR-2 immunoreactivity compared with EDE+PSS. CONCLUSIONS. Disruption of apical corneal epithelial barrier function in dry eye is accompanied by increased apical desquamation and increased expression of cornified envelope proteins. Topical treatment of EDE with the anti-inflammatory agents methylprednisolone or doxycycline preserves apical corneal barrier function.