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S Chen, W Samuel, RN Fariss, T Duncan, RK Kutty, B Wiggert; Differentiation of Cultured Human Retinal Pigment Epithelial (RPE) Cells Into Neuronal Phenotypes Induced by Fenretinide . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4556.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Fenretinide, a synthetic retinoic acid (RA) derivative, used clinically as a cancer suppressor, has been reported to inhibit cell proliferation and induce apoptosis and differentiation in tumor cells. Our purpose in this study was to investigate the effect of fenretinide and other RA derivatives on the human RPE cell line, ARPE-19. Methods: ARPE-19 cells were treated with 0-5 µM fenretinide, 0-10 µM 13-cis RA or 0-5 µM all-trans RA in RA-free medium for 1-4 weeks. After treatment, cells were immunostained with neuronal markers, such as N-CAM, neurofilament and GAD-65, and glial cell marker GFAP. The expression of CRALBP was analyzed by Western blotting. Proteins expressed in control and treated cells were analyzed by 2D gel electrophoresis. Results: 0.5-2.0 µM of fenretinide, but not 13-cis RA, nor all-trans RA, induced ARPE-19 cells to produce long, neurite-like processes. The transition from an epithelial to a neuronal morphology was dose- and time-dependent, starting within 1-2 days of treatment, and persisting up to 4 weeks. The differentiated cells survived for at least 1 week after withdrawal of fenretinide. Further, immunohistochemistry studies demonstrated that the expression of neurofilaments 160 and 200, as well as N-CAM were increased in these differentiated cells. However, they did not show any immunostaining for GFAP, or GAD-65, a marker for interneurons. CRALBP expression was markedly decreased in cells treated with fenretinide for 5 days. 2D gel electrophoresis demonstrated changes in protein expression after fenretinide treatment. Conclusion: We have shown for the first time that fenretinide induces the differentiation of ARPE-19 cells to neuronal phenotypes. Differentiating cells exhibit neuronal morphologies, increased expression of neuron-specific proteins and reduced expression of CRALBP, a protein normally expressed in RPE cells. The identification and characterization of factors capable of guiding the re-differentiation of RPE cells to a neuronal phenotype will provide valuable tools for studying the process of retinal development and a potential pharmacological tool for the treatment of retinal degenerations.
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