Clinical, electroretinographic and histomorphometric evaluation of the retina in sheep with natural scrapie

BMC Veterinary Research

Pierre-Louis Toutain¹  François Schelcher²  Delphine Cayez Gruson¹  Olivier Albaric²  Olivier Andreoletti²  Alain Regnier¹ 

[1] UMR 181 Physiopathologie et Toxicologie Expérimentales, INRA, Ecole Nationale Vétérinaire, 23 chemin des Capelles, B.P. 87614, 31076 Toulouse Cedex 3, France;UMR 1225 Interactions Hôtes-Agents Pathogènes, INRA, Ecole Nationale Vétérinaire, 23 chemin des Capelles, B.P. 87614, 31076 Toulouse Cedex 3, France

关键词: sheep;    scrapie;    retina;    prion;    electroretinography;   

Others  :  1119943
DOI  :  10.1186/1746-6148-7-25

 received in 2010-07-27, accepted in 2011-06-06,  发布年份 2011

【 摘 要 】

Background

The retina is part of the diencephalon in a peripheral location and may be involved in prion diseases. Retinal function and structural changes were assessed in naturally scrapie-affected red face Manech ewes presenting the classical signs of the disease, and clinically healthy age-matched subjects for controls. Ophthalmic examination was done prior to electroretinography (ERG), which was carried out under conditions that allowed photopic and scotopic activities to be assessed. Histomorphometry of the inner and outer retinal layers was performed post-mortem, and retinas were also examined for evidence of abnormal prion protein (PrP^Sc) accumulation and glial fibrillary acidic protein (GFAP) upregulation as a marker of gliosis. Scrapie status was determined by examination of brain tissue

Results

Ocular reflexes and ophthalmoscopy did not reveal any difference between scrapie affected and control animals. Although the light-and dark-adapted ERG responses of both rod-and cone-mediated functions had a similar waveform in scrapie-affected and control sheep, a significant reduction in the amplitude of the ERG a-and b-waves was observed in affected animals compared to controls. These functional alterations were correlated with a substantial loss of cells in the outer nuclear layer (ONL), lengthening and disorganization in photoreceptor segments, and substantial reduction in cellularity and thickness of the inner nuclear layer (INL). The degenerative changes in the INL and ONL were most marked in the central and paracentral areas of the scrapie retinas, and were accompanied in all scrapie retinas by PrP^Sc deposition in the ganglion cell and synaptic layers. GFAP immunoreactivity was mainly increased in the ganglion cell and inner plexiform layers.

Conclusions

No appreciable fundoscopic changes were observed in the scrapie-affected ewes although reproducible changes in retinal function as measured by ERG were observed in these animals. The alterations in the receptoral and post-receptoral pathways corresponded to the degenerative lesions observed in the ONL and INL of the scrapie retinas. The retinal degeneration was associated with prion protein infectivity which presumably spread via the optic nerve.

【 授权许可】

   
2011 Regnier et al; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

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