Artikel
Cellular and subcellular changes in the RPE: from normal aging to early signs of AMD
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Autoren
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Thomas Ach
- Würzburg/D
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K. Bermond
- Würzburg/D
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J. A. Gambril
- Leibniz Institute of Photonic Technology, Jena/D
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C. Wobbe
- Würzburg/D
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A. Berlin
- Würzburg/D
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R. Heintzmann
- Friedrich Schiller University Jena, Institute of Physical Chemistry, Jena/D; Birmingham/USA
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K.R. Sloan
- Birmingham/USA
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C.A. Curcio
- Birmingham/USA
| Veröffentlicht: | 5. Februar 2020 |
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Gliederung
Text
Background: The aged RPE undergoes substantial changes at a cellular/subcellular level, even before AMD lesions are clinically visible with available imaging modalities. Some of these alterations impact RPE geometry and autofluorescence (AF) properties, which then affect clinical fundus AF imaging. Here, we report geometry and intracellular distribution of AF granules in aged RPE to distinguish early AMD changes, which particularly impact RPE integrity and AF characteristics.
Methods: From forty RPE-flatmounts from 40 human donors (15 normals (16-90 years); 25 AMD (80-90 years)), RPE-AF (488 nm excitation) and F-actin cytoskeleton (phalloidin-labeled, 640 nm excitation) were imaged in z-stacks. Using high-resolution structured illumination microscopy, in normal RPE cells, AF granules (lipofuscin, melanolipofuscin, melanosomes) were counted and sub-classified. In AMD eyes, using confocal microscopy, RPE cells were classified for AF pattern and morphology (cell area, AF intensity, number of Voronoi neighbors, and neighborhood of each cell).
Results: In normal aging, RPE cells contain hundreds (mean 300-500) of AF granules, with the lowest number at the fovea and highest at the perifovea. Lipofuscin granules are lowest and melanolipofuscin highest at the fovea. Few melanosomes are found within the RPE cell body. In AMD eyes, RPE geometry (area, number of neighbors) and AF changes. RPE cells re-pack their intracellular granules into aggregates that are expelled from cells, leading to altered and reduced AF/cell. Other cells lose AF granules one-by-one (degranulation). Worsening RPE pathology led to larger cells, reduced AF, and higher variability in number of neighbors.
Conclusion: Information on RPE cell shape/geometry, and number and AF characteristics of intracellular granules help to inform models of normal aging and disease. Foveal AF is mainly driven by melanolipofuscin, even in normal aged eyes. Hyper-AF aggregates seem to be a hallmark of AMD diseased RPE cells – a possible future biomarker for new imaging technologies with subcellular resolution.
Funding: NIH 1R01EY027948 (TA, CAC), 1R01EY06109 (CAC), Dr Werner Jackstädt Foundation (TA)
