Figure 3. Retinal pigment epithelium (RPE) secretion of vascular endothelial growth factor (VEGF) during in vitro polarization. Conditioned media were collected from the apical and basolateral Transwell compartments over the course of 4 weeks and analyzed for VEGF with enzyme-linked immunosorbent assay (ELISA). A: Diagram illustrating Transwell system used for culture of human retinal pigment epithelium (ARPE-19) cells. B: An increase in VEGF secretion preferentially toward the basolateral side was observed during the 4-week culturing. The experiment was performed in triplicate, and the results are expressed as the mean±standard deviation.