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Methylnitrosourea MNU-induced Retinal Degeneration and Regeneration in the Zebrafish: Histological and Functional Characteristics
Published on: October 20, 2014
N -methyl- N -nitrosourea-induced retinal degeneration in mice
Yuan-Yuan Chen1, Shi-Liang Liu1, Dan-Ping Hu1
1Dept of Ophthalmology, Wuhan Univ, Renmin Hospital, Wuhan, China; Eye Institute of Wuhan University, Wuhan, China.
Abstract:
Mouse retinal degeneration models have been investigated for many years in the hope of understanding the mechanism of photoreceptor cell death. N -methyl- N -nitrosourea (MNU) has been previously shown to induce outer retinal degeneration in mice. After MNU was intraperitoneally injected in C57/BL mice, we observed a gradual decrease in the outer nuclear layer (ONL) thickness associated with photoreceptor outer segment loss, bipolar cell dendritic retraction and reactive gliosis. Reactive gliosis was confirmed by increased GFAP protein levels. More serious damage to the central retina as opposed to the peripheral retina was found in the MNU-induced retinal degeneration model. Retinal ganglion cells (RGC) appear to be spared for at least two months after MNU treatment. Following retinal vessel labelling, we observed vascular complexes in the distal vessels, indicating retinal vessel damage. In the remnant retinal photoreceptor of the MNU-treated mouse, concentrated colouring nuclei were detected by electron microscopy, together with the loss of mitochondria and displaced remnant synaptic ribbons in the photoreceptor. We also observed decreased mitochondrial protein levels and increased amounts of nitrosylation/nitration in the photoreceptors. The mechanism of MNU-induced apoptosis may result from oxidative stress or the loss of retinal blood supply. MNU-induced mouse retinal degeneration in the outer retina is a useful animal model for photoreceptor degeneration diseases, such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP).
Insights
N-methyl-N-nitrosourea (MNU) induces outer retinal degeneration in mice, causing photoreceptor cell death and vascular damage. This mouse model aids research into diseases like age-related macular degeneration (AMD) and retinitis pigmentosa (RP).
Area of Science:
- Ophthalmology
- Neuroscience
- Toxicology
Background:
- Mouse models are crucial for understanding photoreceptor cell death mechanisms.
- N-methyl-N-nitrosourea (MNU) is a known inducer of outer retinal degeneration in mice.
Purpose of the Study:
- To investigate the pathological changes and mechanisms of MNU-induced retinal degeneration in C57/BL mice.
- To evaluate the utility of this model for studying photoreceptor degeneration diseases.
Main Methods:
- Intraperitoneal injection of MNU in C57/BL mice.
- Histological analysis of retinal layers (ONL thickness), photoreceptor outer segments, bipolar cells, and RGCs.
- Assessment of reactive gliosis via GFAP protein levels.
- Electron microscopy for ultrastructural analysis of photoreceptors (mitochondria, synaptic ribbons).
- Analysis of vascular damage and mitochondrial protein levels.
Main Results:
- MNU induced progressive outer nuclear layer thinning and photoreceptor outer segment loss.
- Significant reactive gliosis (increased GFAP) and central retinal damage were observed.
- Retinal ganglion cells (RGCs) remained largely spared for two months.
- Evidence of retinal vascular damage, mitochondrial dysfunction (decreased protein levels, loss), and increased nitrosylation/nitration in photoreceptors.
Conclusions:
- MNU-induced retinal degeneration involves photoreceptor apoptosis, potentially due to oxidative stress or compromised blood supply.
- This model effectively mimics key aspects of human retinal degenerations like AMD and RP.
- The model provides valuable insights into photoreceptor cell death pathways and potential therapeutic targets.
