Increased Fundus Autofluorescence and Retinal Cell Infiltration in Middle-Aged Mice Fed with High Fat, Cholesterol-Rich Diet

Abstract

Purpose: Oxidative stress and high plasma cholesterol level have been postulated as contributing to the pathogenesis of various retinal diseases such as age-related macular degeneration and diabetic retinopathy. The purpose of this study is to characterize the retinal phenotype of mice on high fat, cholesterol-rich (HF-C) diet and study the underlying mechanisms that accelerate retinal aging and inflammation.

Methods: B6.129 mice at 12 months of age were fed with either standard rodent chow or HF-C diet, with 5% and 20% (w/w) fat, respectively. The HF-C diet also contained 0.15% cholesterol. Fundus phenotype of both groups was characterized using optical coherence tomography (OCT) and scanning laser ophthalmoscope (SLO) both before and after the HF-C diet for 2 months. Immunohistochemistry and immunofluorescence staining of paraffin or cryosections were performed to further validate findings from the in vivo imaging.

Results: At beginning of the study all animals showed healthy fundus photographs and marginal autofluorescence. Two months after diet change, mice fed with HF-C food showed dome-shaped dotted retinal lesions that were absent in mice on normal diet. SLO revealed significant increase of fundus autofluorescence in HF-C group. Most of the fluorescent spots were in the focal plane of the neuroretina, usually adjacent to retinal vessels. This was also confirmed by OCT scanning. Histology sections of HF-C mice showed increased isolectin- and CD68-positive cells, which were mainly present in the inner plexiform layer as well as the subretinal space.

Conclusions: Feeding high HF-C diet to 12-month old mice could accelerate the retinal aging process, which was presented as elevated fundus autofluorescence. The infiltration of CD68 positive cells indicated microglia and/or macrophages activation that can lead to a pro-inflammatory milieu in the retina and contribute to age-related retinal pathology.

Keywords: 412 age-related macular degeneration • 413 aging • 557 inflammation