Abstract
Purpose :
Malattia Leventinese (ML) is an autosomal dominant inherited macular dystrophy caused by a point mutation (R345W) in the fibulin-3 (fib3) gene (EFEMP1) that presents with sub-retinal pigment epithelium (RPE) deposits and hyperpigmentation. The purpose of this study was to determine if the R345W fibulin-3 makes the retina more sensitive to oxidative stress and if there were any changes that may explain this phenomenon.
Methods :
12 C57Bl/6J three-month old male mice were injected with sodium iodate (NaI) at 22.5 mg/kg. Optokinetic testing was performed pre-injection and 1-, 3-, 5-, and 7 days post-injection. Frozen vertical retinal cross-sections (12 µm thick) of eyes from wild-type (WT), heterozygous (R345W/WT), and homozygous (R345W/R345W) mice were processed for H&E and immunohistochemical (IHC) staining. 12 mice (age, gender, and genotype matched) that were not administered NaI were used for control. Transmission electron microscopy (TEM) was also used to visualize the outer retina.
Results :
Optokinetic testing revealed that the fib3 mutation significantly reduced visual function, indicated by reduced spatial frequency and contrast sensitivity thresholds, compared to controls. H&E cross-sections appeared normal in the control mice, however the retinas of mice that received NaI showed RPE thickening, retinal thinning, and pigmented lesions in the neural retina. The R345W/WT and R345W/R345W mouse retinas are significantly thinner than the WT retinas (24.5 and 18.2%, p<0.0001 and p<0.001) and contained more pigmented lesions (p<0.001 and p<0.0001). IHC indicated that NaI induced vimentin expression in the RPE layer in all retinas, regardless of genotype. IHC of RPE wholemounts of control mice show increased epithelial multinucleation in the mutant mice compared to their WT counterparts (p<0.05). TEM revealed that the mutant mice without NaI administration did not develop basal laminar deposits, or any other notable changes in the outer retina.
Conclusions :
The results suggest that the R345W fib-3 mutation sensitizes the outer retina to NaI-induced injury and accelerates pigment migration into the neural retina prior to the development to the basal laminar deposits previously noted in this model. An early change that may contribute to this sensitivity is the increased RPE multinucleation, as this is linked to genomic instability and increased production of reactive oxygen species.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.