Role of tears in keratocyte loss after epithelial removal in mouse cornea.

PURPOSE To study the role of tears in the death of keratocytes after epithelium removal in the mouse cornea. METHODS In anesthetized mice, an approximately 1-mm circle of epithelium was removed from the center of the cornea, exposing the underlying stroma. In one group of animals, access of tears to the bare stroma was allowed-in vivo, by closing the eyelids, or ex vivo, by dropping tears from another animal onto the denuded stroma of an enucleated eyeball. In another group, tear access was denied-in vivo, by bathing the cornea continuously in saline or by keeping the lids open, or ex vivo, by rinsing the denuded cornea before incubating the enucleated eyeball. In a separate group, corneal epithelial debris from another mouse was placed on the bare stroma of an enucleated eyeball. The corneas were isolated, stained with a fluorescent nuclear dye, and observed en face in a wholemount preparation under a fluorescence microscope, to evaluate the distribution of intact nuclei across the entire depth of the stroma. RESULTS Between 1.5 and 2 hours after exposure to tears, the nuclei of the anterior keratocytes under the area of epithelial debridement invariably degenerated. When they had been protected from the tears, however, no degeneration was observed. Epithelial debris applied on the bare stroma had no effect on the underlying keratocytes. CONCLUSIONS Factors in tear fluid trigger keratocyte loss after removal of the epithelium in the mouse cornea.