Evaluation of Corneal Damage After Lacrimal Gland Excision in Male and Female Mice

PURPOSE: Lacrimal gland excision (LGE) has been utilized in several studies to model aqueous tear deficiency, yet sex as a biological variable has not been factored in to these reports. This study compared corneal pathology in male and female mice following LGE-induced dry eye. METHODS: An LGE of either the extraorbital lacrimal gland (single LGE) or both the extraorbital and intraorbital lacrimal glands (double LGE) was performed in male and female C57BL/6J and Balb/cJ mice to produce dry eye of graded severity. Following excision, tearing was evaluated with phenol red thread, and corneal fluorescein staining was scored to quantify the severity of damage. Corneas were evaluated for apoptosis by the TUNEL assay and for cell proliferation using Ki67 staining. Furthermore, corneas were harvested and analyzed for macrophages via flow cytometry. RESULTS: Baseline tearing levels were similar in male and female mice, and LGE resulted in comparable reductions in tearing with the lowest levels recorded after double LGE. As determined by fluorescein staining, LGE produced more severe damage to the cornea in female C57BL/6J and Balb/cJ mice. Double LGE increased TUNEL and Ki67 staining in the cornea, with greater increases found in female mice. Furthermore, LGE produced a greater increase in the total number of corneal macrophages in female mice. CONCLUSIONS: These results indicate that female mice are more susceptible to LGE-induced corneal damage. The mechanisms involved in producing these sex differences still need to be elucidated but may involve increased inflammation and macrophage infiltration.