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A. Dobias, A. K. Salz, P. Walter, G. Thumann; Phagocytic Activity of ARPE-19 Cells on Biological and Artificial Substrata. Invest. Ophthalmol. Vis. Sci. 2010;51(13):486.
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Vision recovery in retinal degeneration first requires the replacement of degenerated RPE cells and secondly, the transplanted cells must be able to communicate with the exposed photoreceptors and fulfill the critical function of phagocytizing outer segments (OS). Since transplantation of cell suspensions does not lead to vision recovery, it will be necessary to transplant cells as preformed monolayers on a biocompatible substrate. To evaluate the influence of the substrate on phagocytosis we have investigated the phagocytic activity of pigment epithelial cell monolayers grown on silk, amniotic membranes, and plastic.
ARPE-19 cells were cultured on biologic human amniotic membranes, silk membranes, and plastic. When the cells reached 80% confluence they were exposed to unlabeled or FITC-labeled photoreceptor outer segments for 24 hours at 37°C and at 4°C to inhibit internalisation. After 24 hours the cells were trypsinized and fluorescence intensity was determined using flow cytometric analysis. Data are expressed as the median fluorescent index (MFI) of 5000 cells (n=4). The fluorescence at 4°C was assumed to be surface-bound ROS and was subtracted from fluorescence at 37°C.
After 24 hours at 4°C fluorescence intensity was similar on all three substrata. The MFI on plastic was 3.1, on silk 3.7 and on amniotic membranes was 5.2. After 24 hours at 37°C fluorescence intensity was significantly higher on amniotic membranes and on silk than on plastic. The MFI on plastic was 152.4, on amniotic membranes 270.6, a 78% increase, and on silk 261.6, a 70% increase.
The results show that OS phagocytosis is influenced by the substratum and that natural biodegradable substrata enhance the phagocytic activity of retinal pigment epithelial cells. Cells on biomaterials adhere and develop the right polarity to accomplish the essential RPE functions.
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