ObjectiveTo observe the effect of exosomes derived from human umbilical cord blood mesenchymal stem cells (hUCMSC) on the expression of vascular endothelial growth factor (VEGF) A in blue light injured human retinal pigment epithelial (RPE) cells. MethodshUCMSC were cultured with exo-free fetal bovine serum for 48 hours, and then the supernatants were collected to isolate and purify exosomes by gradient ultracentrifugation method. Transmission electron microscopy was used to identify the morphology of exosomes. Surface specific maker protein CD63 and CD90 were detected via Western blot. Cultured ARPE-19 cells were divided into normal control group, blue light injured group and hUCMSC exosomes treated group. Cells were exposed to the blue light at the intensity of (2000±500) Lux for 12 hours to establish the light injured models. The cells of hUCMSC exosomes treated group were treated by different concentrations of exosomes for 8, 16, 24 hours. The mRNA and protein of VEGF-A were determined by real time-polymerase chain reaction and Western blot. Immunofluorescence assay were used to detect the expression levels of VEGF-A. ResultshUCMSC exosomes were successfully isolated, they exhibited round or oval shape and their diameter ranged from 50 to 100 nm with membrane structure through electron microscope. hUCMSC exosomes expressed the common surface marker protein CD63 and the surface marker protein CD90 of hUCMSC. The protein and mRNA level of VEGF A in the blue light injured group increased significantly compared to that in normal control group (t=-16.553, -19.456; P < 0.05). After treating with low, middle and high concentration of hUCMSC exosomes for 8, 16 and 24 hours, the protein and mRNA level of VEGF A of injured RPE were significantly decreased (P < 0.05). With the treated time and concentration of hUCMSC exosomes improved, the protein and mRNA level of VEGF A of injured RPE gradually decreased (P < 0.05). Immunofluorescence assay showed the protein level of VEGF-A of injured RPE gradually decreased with the same concentration of hUCMSC exosomes treated over time. ConclusionhUCMSC exosomes can effectively down-regulate the mRNA and protein level of VEGF-A in blue light injured RPE, the effect depends on the concentration and treated time of hUCMSC exosomes.