Purchase this article with an account.
Mariusz Zareba, Tadeusz J. Sarna, Janice M. Burke; The Ratio of Melanosome to Lipofuscin Granule Number, Not Lipofuscin Content Alone, Determines the Susceptibility of Individual RPE Cells to Lethal Photic Stress in vitro. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4273.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Autofluorescent lipofuscin is believed to predispose the aging RPE to photic stress. Since RPE cells vary in the content of both photo-reactive lipofuscin granules and photo-protective melanosomes, we asked whether individual RPE cell susceptibility to light-induced injury depended on lipofuscin abundance alone, or could be modulated by coincident melanosome content.
Primary cultures of human RPE containing varying numbers of lipofuscin granules were allowed to phagocytize isolated porcine melanosomes (pigment granules unmodified by age) or control black latex beads. Individual cells in sub-confluent cultures were selected for their granule number and their ratio of granule types using absorbance to quantify total granule number per cell, autofluorescence to identify lipofuscin, and latex fluorescence (635-685, excitation-emission) to detect beads. Cells were irradiated with blue light (490 nm) and the time of cell death after light onset was determined by real-time live cell imaging using image capture at 30 s intervals over 8 hrs.
Cell death induced by blue light varied with lipofuscin content; cells with abundant endogenous lipofuscin died first while those with fewer lipofuscin granules showed delayed death or survived irradiation. The presence of melanosomes within cells in addition to lipofuscin delayed cell death as compared to cells with comparable amounts of lipofuscin alone. Preliminary results showed no significant death delay in cells containing beads, suggesting that the protective effect of melanosomes was at least partly due to properties of the pigment (e.g., acting as an antioxidant) aside from optical screening.
RPE cells are exposed throughout life to blue light.The results here suggest that the content of autofluorescent lipofuscin alone may not be an effective predictor of the photic stress susceptibility of the tissue. Since the vulnerability to stress differs among individual cells, a better predictor of an at-risk monolayer may be the frequency of RPE cells with both high lipofuscin content and low melanosome number.
This PDF is available to Subscribers Only