Purpose
Oxidative damage has been proposed as a contributing factor in the development of age-related macular degeneration (AMD). We tested the hypothesis that systemic iron overload, as a result of specific Hfe gene mutations, results in excess iron deposition and oxidation-induced damage consistent with AMD in two experimental mouse models.
Methods
Researchers evaluated ocular specimens from mice with the H63D and C282Y mutation of the Hfe gene. For the H63D mutation, 12 ocular specimens from mice of mixed C57BL/6J and 129X1 background were collected after the animals were humanely killed. The mice were 18 months old, age- and sex- matched with six mice homozygous for the H63D mutation (Hfetm2Sly) and six wild-type (WT). In the C282Y population, 30 specimens from mice of 129/SvlmJ background were collected, five males and five females from each of the following populations: homozygous C282Y mutation, heterozygous C282Y/WT, and WT. All eyes were fixed in Bouin’s solution and tissues were processed in an automated Tissue-Tek VIP processor and paraffin-embedded with a Tissue-Tek TEC embedding station (Sakura Finetek USA, Torrance, CA). Sections were cut at 6 µm for hematoxylin and eosin (H&E) or periodic acid-Schiff (PAS) stain. All tissues were examined by an ACVP diplomate veterinary pathologist blinded to genotype and sex.
Results
Histopathologic examination of the H63D ocular specimens, both WT and mutant, showed normal pathology on H&E (Figure A-1, A-2). There was no evidence of positive iron staining present in any of the specimens (Figures A-5, A-6). Examination with PAS revealed no drusen, atrophy, neovascularization, or photoreceptor degeneration (Figures A-3, A-4). In C282Y heterozygotes, there was no evidence of iron deposition or free radical damage (B1-B6).
Conclusions
Ocular specimens from mice with the H63D and C282Y mutation did not demonstrate accumulation of iron within the retina despite evidence of systemic iron accumulation. Without the deposition of iron and subsequent free radical elaboration, the experimental model could not provide evidence as to the effect of oxidation in the development of AMD.