Abstract
Purpose: :
Mice harboring a null mutation in Abca4/Abcr serve as a model of autosomal recessive Stargardt disease. Consistent with the human retinal disorder, deficiency in Abcr is associated with substantial accumulations of lipofuscin pigments in the retinal pigment epithelial cells. We sought to characterize photoreceptor cell degeneration in this mutant mouse line.
Methods: :
Using digital images of Abcr+/+ and Abcr-/- retina, outer nuclear layer thickness was measured at 200 microns intervals superior and inferior to the optic nerve head. The numbers of photoreceptor nuclei spanning the width of the outer nuclear layer were also counted in superior hemiretina at a distance of 600 microns from the edge of the optic nerve head.
Results: :
ONL width in Abcr-/- mouse was reduced at 8-9 month and 11 and 13 months relative to Abcr+/+ mice. The decrease in ONL thickness in Abcr-/- mice was more pronounced centrally and in superior retina. The numbers of photoreceptor cell nuclei across the breadth of the ONL were also reduced. No evidence of age-related ONL thinning was observed in Abcr+/+ mice at these ages.
Conclusions: :
Albino Abcr-/- mice exhibit progressive photoreceptor cell loss that is detectable at 8 months of age and that has worsened by 11 and 13 months of age. Thinning of the ONL was more marked in the superior hemi-retina. The measurement of outer nuclear layer thickness is an established approach to assessing photoreceptor cell integrity that can be used in preclinical studies using Abcr-/- mice.
Keywords: photoreceptors • retinal degenerations: hereditary • ipofuscin