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Dinusha Rajapakse, Mei Chen, Heping Xu; Photoreceptor outer segment (POS) suppresses RPE cell proliferation and induces multi-nucleation.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2323.
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© ARVO (1962-2015); The Authors (2016-present)
Compelling evidence suggests that retinal pigment epithelial (RPE) cells undergo multinucleation during ageing. The underlying mechanism and the functions of multinucleated RPE are yet to be elucidated. We hypothesise that RPE cells multinucleate during ageing to compensate for impaired function of senescence and photoreceptor outer segment (POS) plays an important role in RPE cell multinucleation.
ARPE-19 cells were cultured in DMEM/F-12 and treated with 1x106/ml POS for 48h. Cell nuclei were stained with DAPI and centrosomes with γ-tubulin to determine multinucleated cells. RPE phagocytosis was performed using the FITC conjugated E-coli bio-particles and analysed by confocal microscopy and flow cytometry.
POS treatment dose-dependently suppressed ARPE-19 cell proliferation. After 48h POS-treatment, 33% of cells were multinucleated compared to 5% in untreated control ARPE-19 cells (P<0.05). Confocal microscopy revealed multiple centrosomes in multinucleated RPE cells, an indicative of cytokinesis failure. Multinucleated RPE cells phagocytosed significantly more E. coli bio-particles (per cell) compared to mononucleated cells (P<0.01). Flow cytometry analysis revealed a positive correlation between DNA content and fluorescent intensity of phagocytised E. coli (P=0.02).
Multinucleated RPE cells appear to have a normal phagocytosis function. POS has a significant impact on RPE cell proliferation and cytokinesis, and can induce RPE cell multinucleation. Further studies on the mechanism of POS-induced RPE multinucleation and the function of multinucleated cells will be crucial for understanding the patho-physiology of RPE cells in the ageing eye and in age-related retinal degeneration.
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