Development of Animal Models for Lens and Corneal Diseases Using N-Methyl-N-Nitrosourea

PURPOSE: N-methyl-N-nitrosourea (MNU) is an alkylating toxicant with potent mutagenic ability. This study was designed to induce apoptosis in lens epithelial cells (LECs) and corneal endothelial cells (CECs) via MNU administration. We sought to build ocular disease models of cataract and corneal endothelial decompensation. METHODS: MNU was delivered into the intraperitoneal cavities of neonatal rats and the anterior chambers of adult rabbits. The MNU-treated animals were then subjected to a series of functional and morphological analyses at various time points. RESULTS: MNU treatment induced pervasive apoptosis of LECs and CECs. These effects were dose and time dependent. Mature cataracts were found in neonatal rats 3 weeks after MNU treatment. Histological analysis revealed that MNU toxicity induced swelling, vacuolation, and liquefaction in lens fibers of MNU-treated rats. Pentacam examination showed that the average density of rat lens increased significantly after MNU administration. Terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) analysis showed pervasive apoptotic staining in the lenses of MNU-treated rats. In rabbit eyes, intracameral treatment with MNU induced corneal edema and significantly increased central corneal thickness, which peaked at P14. Morphological and immunohistochemical analysis showed that CECs were effectively ablated in the MNU-treated rabbits. The expression of 8-OHdG increased significantly in the cornea of MNU-treated rabbits, compared with vehicle-treated controls. CONCLUSIONS: MNU is sufficient to induce ocular cell apoptosis in animal models. These models of MNU-induced cataract and corneal endothelial decompensation represent valuable tools for efforts to develop relevant therapies.