Effects of ROBO4 depletion by transcriptional regulation or miRNA modulation on ARPE‐19 cell viability, monolayer permeability and migration under hyperglycaemic and hypoxic conditions. A, Changes in the viability of ARPE‐19 cells under HG following inhibition of SP1 or ROBO4 or up‐regulation of miR‐125b‐5p over time. B, Changes in the viability of ARPE‐19 cells under hypoxic conditions following knockdown of HIF‐1α or ROBO4 or overexpression of miR‐146a‐5p over time. C, D, Permeability was analysed by detection of the leakage of FITC‐dextran across cells in monolayer culture under hyperglycaemic or hypoxic conditions following transfection with siRNA or miRNA mimic. E, F, Representative photomicrographs showed the migrated cells in transwell assays. Migrated cells were counted at a magnification of 10×. NG, normal glucose. In HG experiments, *P < 0.05; **P < 0.01; ***P < 0.001 versus NG. In hypoxic studies, **P < 0.01; ***P < 0.001 versus NC; #
P < 0.05; ##
P < 0.01; ###
P < 0.001 versus negative transfection (n = 3). Hypo, hypoxia; NC siR, negative transfection