Einfluss von Octreotid in Kombination mit Wachstumsfaktoren auf die Proliferation von RPE-Zellen in vitro

Background. The long-acting somatostatin analogue octreotide is used as a therapeutic option for patients with diabetic retinopathy and age-related macular degeneration. Growth factors, such as EGF, bFGF,VEGF, and PDGF, have been implicated in the pathogenesis of these diseases.The aim of this study was to investigate the effect of octreotide on the growth-factor-induced proliferation of bovine retinal pigment epithelial (RPE) cells in vitro. Methods. RPE cells were assayed for proliferation as measured by ( 3 H)-thymidine uptake (ccpm). Bovine RPE cells at passage 3-8 were seeded in a 96-well plate and incubated for a 24-h period with a minimum medium followed by a 24-h incubation with the different growth factors at a concentration of 10 ng/ml with and without 5×10 -5 M octreotide. In a different assay the cells were incubated with octreotide at 5×10 -10 -5×10 -4 M. Afterwards the cells were pulsed with 5 μCi/ml ( 3 H)-thymidine for 12 h, and the incorporated radioactivity was measured on glass fiber filters in a beta-counter (mean±SEM ccpm).The Wilcoxon Signed Rank test and the student's t-test were used for statistical analyses. Results. There was a biphasic effect of octreotide on RPE cell proliferation. Exposure of RPE cells to PDGF (20,225±3304 ccpm) and bFGF (3441±539 ccpm) resulted in a significantly higher proliferation compared to control medium (1543±352 ccpm) (p<0.05). No difference was found for EGF (2385± 383 ccpm).ForVEGF (776±83 ccpm) a significant reduction in RPE cell proliferation was found (P<0.05).There was a significant reduction in proliferation of RPE cells with PDGF, bFGF, and EGF in combination with octreotide versus growth factors alone (octreotide in combination with PDGF 308±82 ccpm,with bFGF 229±88 ccpm, with EGF 2362±91 ccpm) (p<0.005).VEGF in combination with octreotide resulted in a significant inhibition of RPE cell proliferation compared to VEGF alone (p<0.0005). Conclusion. The data suggest that there is an inhibitory effect of octreotide on RPE cell proliferation of bovine RPE cells and on the increased proliferation of bovine RPE cells induced by PDGF and bFGF. An enhanced inhibitory effect is found for the combination of octreotide and VEGF.