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Morphologic characteristics of N-methyl-N-nitrosourea-induced retinal degeneration in C57BL mice
1Department of Pathology, Kansai Medical University, Osaka, Japan.
Abstract:
Morphologic characteristics of retinal degeneration induced by a single systemic administration of N-methyl-N-nitrosourea (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 intraperitoneally into male and female C57BL mice, evoked progressive retinal degeneration in all treated mice, while control mice remained normal. An early change was photoreceptor apoptosis followed by infiltration of macrophages and swelling of the pigment epithelial cells with phagosomal inclusions for apoptotic photoreceptor cell removal. Loss of the majority of photoreceptor cells occurred within a week. Then, Feulgen-positive corpuscles, 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 sclerad 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 epithelial cells. As in retinitis pigmentosa in humans, the primary event was loss of photoreceptor cells by apoptosis, but the migration of the pigment epithelial cells within the retina was not seen in the present model.
Insights
This study investigated N-methyl-N-nitrosourea (MNU)-induced retinal degeneration in mice, revealing photoreceptor apoptosis and subsequent cellular changes. The model mimics some aspects of human retinitis pigmentosa but lacks pigment epithelial cell migration.
Area of Science:
- Ophthalmology
- Neuroscience
- Toxicology
Background:
- Retinitis pigmentosa is a group of inherited diseases that cause vision loss.
- Animal models are crucial for understanding retinal degeneration mechanisms.
- N-methyl-N-nitrosourea (MNU) is a chemical agent known to induce mutations and cellular damage.
Purpose of the Study:
- To characterize the morphologic features of retinal degeneration induced by N-methyl-N-nitrosourea (MNU) in mice.
- To compare the MNU-induced retinal lesions in mice with human retinitis pigmentosa.
- To evaluate MNU as a potential model for studying retinal degeneration.
Main Methods:
- Single intraperitoneal administration of 60 mg/kg body weight N-methyl-N-nitrosourea (MNU) to male and female C57BL mice.
- Morphologic investigation of retinal changes over time using histopathological techniques.
- Comparison of observed lesions with known features of human retinitis pigmentosa.
Main Results:
- MNU induced progressive retinal degeneration in all treated mice, characterized by photoreceptor apoptosis.
- Early changes included macrophage infiltration and pigment epithelial cell swelling for debris removal.
- Within a week, a majority of photoreceptor cells were lost, followed by Feulgen-positive corpuscles and Müller cell involvement.
- The model showed similarities to human retinitis pigmentosa, particularly the primary photoreceptor cell loss via apoptosis.
Conclusions:
- MNU is an effective agent for inducing retinal degeneration in mice.
- The MNU-induced model exhibits key features of human retinitis pigmentosa, including photoreceptor apoptosis.
- Differences were noted, such as the absence of pigment epithelial cell migration in the mouse model, suggesting limitations for direct comparison.