Effect of Insulin-Like Growth Factors 1 and 2, and Glucose on the Migration and Proliferation of Bovine Retinal Pigment Epithelial Cellsin vitro

Abstract

Background: The retinal pigment epithelium (RPE) has been implicated in the development of diabetic retinopathy and it has been suggested that insulin-like growth factors (IGF) and glucose may be among those factors which are responsible for the RPE changes in diabetics. The purpose of this study was to investigate the effect of IGF-1, IGF-2, and glucose on the migration and proliferation of bovine RPE cells in vitro. Methods: Primary cultures of bovine RPE cells were established from freshly enucleated eyes and passages 5–8 were used for these experiments. RPE cell migration was studied in confluent RPE cultures grown in multiwell plates. After inhibition of proliferation with mitomycin C (10 µg/ml) and partial denudation of the RPE in each well, the cells were incubated with IGF-1 (10 ng/ml), IGF-2 (10 ng/ml) or glucose (10 mM). Migration was measured as the number of cells that had entered the denuded area after 20 h. RPE cell proliferation was determined by [³H]-thymidine incorporation after incubation with IGF-1, IGF-2, and glucose for 24 h. Statistical analysis was performed with the paired Student’s t test. Results: Exposure of RPE cells to IGF-1, IGF-2, and glucose resulted in a significantly higher RPE cell migration as compared to the control medium (p < 0.008) with 21, 20, 17, and 9 cells/raster field, respectively. Additionally, IGF-1 (p = 0.004) and IGF-2 (p = 0.008) but not glucose caused a statistically significant stimulation of DNA synthesis with 761, 747, and 593 ccpm, respectively, as compared to the negative control (352 ccpm). Conclusion: This study indicates that IGF-1 and IGF-2 influence RPE cell migration and proliferation. This is further evidence that these factors are among those which have to be kept in mind when trying to modulate the development of diabetic eye diseases.