98th Annual Meeting DOG 2000

V 153

Restoration of photoreceptor outer segments and function in retinal degeneration slow (rds) mice by gene therapy

G.-M. Sarra1, C. Stephens1, J. B. L. Bainbridge1, S. Fauser3, M. B. Reichel1, R. R. Ali1,2

Background: Mutations in the peripherin/rds (retinal degeneration slow) gene which encodes a photoreceptor-specific membrane glycoprotein, have been shown to result in a variety of retinal phenotypes, including autosomal dominant retinitis pigmentosa and macular dystrophy. Many aspects of the human disease are reflected by the retinal degeneration slow (rds) mouse, which in the homozygous form is characterised by a complete failure to develop photoreceptor outer segments. Heterozygous animals also develop progressive retinal degeneration due to semi-dominant haploinsufficiency. The aim of this study was to test the feasibility of treating photoreceptor cell defects by gene replacement therapy.

Methods: Juvenile homozygous rds mice were subretinally injected with recombinant AAV containing a peripherin/rds cDNA driven by a photoreceptor cell-specific rhodopsin promoter (AAV.rho.rds) or containing a GFP reporter gene driven by a CMV promoter (AAV.CMV.GFP). Procedured eyes taken at various time points up to 20 weeks following injection were analysed by immunohistochemistry, scanning and transmission electron microscopy.

Results: Photoreceptor cells transduced with AAV.rho.rds produce discs that contain rhodopsin, and develop outer segment structures. Electroretinography (ERG) was performed on AAV.rho.rds and AAV.CMV.GFP treated animals and whilst there was no detectable ERG in control animals, a significant b wave was observed in AAV.rho.rds treated animals.

Discussion: The feasibility of treating photoreceptor cell defects by gene replacement therapy has been unambiguously demonstrated. This is the first time that an ultrastructural defect has been significantly improved in any model of human disease.

1 Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
2 Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
3 University Eye Clinic, Waldhoernlestrasse 22 D-72072 Tuebingen
4 University Eye Clinic, Liebigstrasse 10-14, D-04103 Leipzig