Abstract
Purpose::
RPE is an essential cell layer in the visual system, it plays a central role in the eye as it has physical, optical, metabolic, biochemical and ion transport functions . It is also implicated in retinal inflammation and degeneration. In this study, we used one cell line, RPE-19 to analyse the expression of pro inflammatory and angiogenic factors in vitro.
Methods::
The angiogenic potential of RPE-19 was evaluated by total RNA genomic profiling using microarray analysis (1800 genes) after 10-8 M triamcinolone treatment. RPE-19's supernatant angiogenic activity was tested by human bone marrow endothelial cells (HBMEC) network-formation on a semi solid matrix (MatrigelTM), growth factor reduced. VEGF, b-FGF, Il-3, stromal derived factor (SDF1alpha) secreted by RPE cell were quantified by ELISA. Intracytoplasmic VEGF and SDF1alpha in RPE cell were assayed by immunocytochemistry using specific antibodies.
Results::
Microarray analysis shows the expression of pro-angiogenic and angiogenic factors, including several interleukins such as 1A, 2, 3, 5, 8, 9, 10, 11, 12A, 13, 16, 17, 18 and 21. Angiogenic factors such as VEGF A, B, C, SDF-1, Insulin like growth factor, beta-transforming growth factor (TGF-b) 1, 3 as well as cystein rich angiogenic inducer were also detected. Cytokines receptor such as TGFRb-1, 2 and interleukins receptors 1, 7 and 13 were expressed. SDF1alphareceptor CXCR4, neuropillin -1, and VEGF co-receptor were also found. Differential gene expression study between untreated and treated cells only shows IL18 (interferon gamma inducing factor) up-regulation and VEGF-A (a vascular permeability factor (VPF)) down-regulation. In vitro angiogenesis study shows VEGF, FGF and SDF1alpha presence in RPE cells’ supernatants and theses factors were immunolocalised in cells. Therefore RPE cell are able to enhance network-formation of HBMEC on MatrigelTM. Furthermore RPE cell’s supernatant can inhibit network formation of HBMEC on Matrigel. This paradox can be attributed to RPE cells’ secretion of PEDF . Our results suggest that RPE cell’s supernatants degrade the VEGF receptors on the HBMEC.
Conclusions::
The expression of interleukines and angiogenic factors by RPE cells show the crucial role of the RPE cell layer in ocular inflammation, subretinal neovascularization and tumour progression. The role of these factors detected in RPE cells, and their implication in physiological process, such as metabolic, biochemical and ion transport functions are to be explored.
Keywords: retinal neovascularization • vascular cells • choroid: neovascularization