Novel Spatial Imaging Techniques for Ocular Retinoids and Retinoid Adducts

Medical University Of South Carolina, Charleston SC

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Abstract

DESCRIPTION (provided by applicant): Age-related degenerations, including AMD, are the leading cause of vision loss and blindness in America today. One of the most striking features of the aging eye is the accumulation of autofluorescent lipofuscin granules in the macular area of the RPE. Lipofuscin is a complex mixture of compounds, many of which are bis-retinoid based. To date, over 20 bis-retinoids have been isolated and characterized from lipofuscin, A2E being the best studied. However, current methodologies do not allow for high spatial localization of these products. The assumption has been that the distribution of the products will correlate with the fluorescence of lipofuscin. We propose to develop matrix-assisted laser desorption ionization (MALDI) imaging methodologies for retinoid compounds and adducts in the RPE/choroid, which will allow both the identification of individual compounds and the determination of their spatial distribution in a single experiment. These compounds will be detectable at a resolution of 10-50 5m and relative quantization can be obtained. This imaging technique has been used for proteins, lipids and metabolites, but never for retinoids and not with retinal/choroid tissue. Our aims are 1) to develop this technology for a range of retinoids in the mouse RPE/choroid and 2) extend these studies to the more relevant human RPE/choroid. This would represent a major breakthrough in identifying the localization of bis-retinoid adducts in the RPE/choroid. Preliminary data demonstrate that A2E can be localized across the RPE/choroid at high resolution by this technique. Our findings show that in the human retina, the A2E levels do not correlate with the fluorescence attributed to lipofuscin. Imaging other bis-retinoid products and retinoid based compounds needs further development and is the focus of this project. The successful development of this technique will provide new and critical information to researchers studying approaches to the treatment and/or prevention of AMD and other retinal/RPE disorders.