Retinopathy in mice with experimental scrapie

Area of Science:

• Neuroscience
• Ophthalmology
• Veterinary Pathology

Background:

• Scrapie is a fatal, naturally occurring neurological disease affecting adult sheep and goats.
• The disease has a long incubation period, typically several years.
• Scrapie agent strains can infect laboratory mice, serving as a model for studying disease progression.

Purpose of the Study:

• To investigate the occurrence and severity of retinopathy in murine scrapie models.
• To determine the influence of scrapie agent strain and mouse genotype on retinopathy development.
• To explore potential correlations between retinopathy and central nervous system pathology or incubation period.

Main Methods:

• Infection of various mouse genotypes with different scrapie strains.
• Histopathological examination of retinal tissues to assess photoreceptor layer integrity.
• Evaluation of vacuolar degeneration in brain tissues, including areas controlling pupillary constriction.
• Comparison of retinopathy severity with scrapie incubation periods.

Main Results:

• Retinopathy, characterized by photoreceptor loss, was observed in some, but not all, murine scrapie models.
• The severity of retinopathy was significantly influenced by both the scrapie strain and the host mouse genotype.
• Certain scrapie strains (e.g., 79A, 139A) consistently induced retinopathy across all tested mouse genotypes.
• Other strains showed genotype-dependent retinopathy, while some caused minimal or no retinal pathology.
• Retinopathy severity did not correlate with overall brain vacuolation, specific brainstem vacuolation, or disease incubation period.

Conclusions:

• Murine scrapie models exhibit variable retinopathy, highlighting the impact of agent strain and host genetics.
• Retinopathy in scrapie is a distinct pathological feature that does not necessarily mirror the extent of central nervous system neurodegeneration.
• Further research into the mechanisms underlying scrapie-induced retinopathy is warranted.