Comparative study of ROS degradation by IPE and RPE cells in vitro

Background: The aim of this study was to compare the degradation of rod out er segments (ROS) in porcine iris pigment epithelial cells (IPE) and retina l pigment epithelial (RPE) cells by measuring the increase of lipofuscin-li ke fluorescence. Methods: We measured the development of autofluorescence o f lipofuscin-like material in living cells over a period of 4 weeks using a n image-analyzing system comprising a light microscope, a filter set with a n appropriate wavelength for the detection of lipofuscin-like autofluoresce nce and a silicon-intensified target camera connected to a computer. The li pofuscin-like fluorescence was quantified as the mean gray value of pixels over a defined area in the cell. In addition, ultrastructural examination o f the cells was performed using transmission electron microscopy. Results: We found that while both cell types had increased autofluorescence over tim e, the increase of lipofuscin-like fluorescence was significantly higher in IPE cells than in RPE cells. The ultrastructure of both cell types was sim ilar and no accumulation of lipofuscin-like granules was observed. Conclusi on: These findings suggest that allthough IPE cells are able to phagocytize ROS, their ability to degrade them may be lower than in RPE cells. The inc rease of lipofuscin-like fluorescence is not due to the accumulation of lip ofuscin-like granules.