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Kevin Schey, David MG Anderson, Kate H. McKinney, Jeffrey D Messinger, N. Heath Patterson, Jeffrey M. Spraggins, Christine Curcio; Molecular Landscape of the Human Macula by High Resolution Imaging Mass Spectrometry. Invest. Ophthalmol. Vis. Sci. 2019;60(11):010.
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© ARVO (1962-2015); The Authors (2016-present)
Imaging mass spectrometry (IMS) is a powerful tool for elucidating spatial distributions of biomolecules ranging from lipids to metabolites to proteins. With low micrometer spatial resolution, molecular distributions can be distinguished between cell and synaptic layers of human retina. The purpose of this work is to map the distribution of lipids and molecular pigments of normal and age-related macular degeneration (AMD) human macula.
Paraformaldehyde-preserved eyes from human donors 80-93 years of age were analyzed in both macula and peripheral regions. Adjacent serial sections were stained with Periodic acid-Schiff and Hematoxylin stains for morphological analysis. IMS was performed at 5-15 µm spatial resolution in positive and negative ion modes on a Bruker Solarix 9.4T FTICR instrument with a modified MALDI source designed for high spatial resolution imaging experiments. Tissue autofluorescence images were also acquired from sections, before and after IMS experiments, to enable precise registration of IMS and optical signals, allowing high-confidence localization of IMS signals to individual layers and extracellular deposits.
Specific lipid signals observed in IMS images correlate with tissue regions, i.e. the fovea and tissue layers, i.e., retinal pigment epithelium (RPE), photoreceptor cells, and Henle fiber layer. High spatial resolution IMS combined with registration to autofluorescence and H&E images, enabled definitive localization of signals to the layers of the RPE cell bodies and apical processes as well as vertically aligned compartments of photoreceptor cells. An abundant signal observed at (m/z 799.676) was identified as PE-Cer-NMe2(42:1) and in a normal eye, localized to RPE apical processes/ outer segments below the fovea and extending out to the periphery. This lipid is also observed with very high abundance in a basal laminar deposit present in a 93 year old eye with AMD. Detection of distinct lipid signals present in drusen and basal laminar deposits were also observed. Signals attributed to lutein/zeaxanthin were detected in the foveal center. Molecular profiles of macular RPE cells differed from peripheral RPE cells.
IMS allowed mapping of specific lipid and molecular pigment signals in retinal regions and layers. Unique molecular signatures were detected for specific retina cell layers and extracellular deposits.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
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