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 epith elium removal in the mouse cornea. METHODS. In anesthetized mice, an approximately 1-mm circle of epithelium w as removed from the center of the cornea, exposing the underlying stroma. I n one group of animals, access of tears to the bare stroma was allowed-in v ivo, by closing the eyelids, or ex vivo, by dropping tears from another ani mal onto the denuded stroma of an enucleated eyeball. In another group, tea r access was denied-in vivo, by bathing the cornea continuously in saline o r by keeping the lids open, or ex vivo, by rinsing the denuded cornea befor e incubating the enucleated eyeball. In a separate group, corneal epithelia l 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 micr oscope, to evaluate the distribution of intact nuclei across the entire dep th 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 d egenerated. When they had been protected from the tears, however, no degene ration was observed. Epithelial debris applied on the bare stroma had no ef fect on the underlying keratocytes. CONCLUSIONS. Factors in tear fluid trigger keratocyte loss after removal of the epithelium in the mouse cornea.