Morphologic characteristics of N‐methyi ‐N‐nitrosourea‐induced retinal degeneration in C57BL mice

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Abstract
Morphologic characteristics of retinal degeneration induced by a single systemic administration of Methyl‐Knitro‐sourea (MNU) in mice was Investigated. The aim was to characterize the MNU‐Induced retinal lesions In mice and compare them with human retinitis pigmentosa. A dose of 60 mg/kg body weight MNU, Injected intraperttoneally into male and female C57BL mice, evoked progressive retinal degeneration in all treated mice, while control mice re mined normal. An early change was photoreceptor apoptosis followed by Infiltration of macrophages and swelling of the pigment epithellal cells with phagosomal inclusions for apoptotic photoreceptor cell removal. Loss of the majority of photoreceptor cells occurred within a week Then, Feulgenpositive corpuscies, indicative of an aggregation of degenerative photoreceptor elements, vitread the outer limiting membrane were surrounded by Müller cell processes, and the duplication of the pigment epithelial cells sciurid the outer limiting membrane were seen 2 and 3 weeks after the treatment. Finally, the Feulgen‐positive corpuscles disappeared and Müller cell processes were in direct contact with the continuous lining of the single layer of pigment epithellal cells. As in retinitis pigmentosa in humans, the primary event was loss of photoreceptor cells by apoptosis, but the migration of the pigment epithellal cells within the retina was not seen in the present model.