gms | German Medical Science

Increased vascular permeability is a major problem in diabetic retinopathy. Though, currently used therapies are often unable to stop leakage of retinal vessels permanently. To develop new therapeutic approaches it is important to know the cellular and molecular mechanisms leading to vascular leakage. The aim of this study is to investigate the cross talk between Vascular Endothelial Growth Factor (VEGF) and Angiopoietin-2 (Ang-2) acting on retinal endothelial cells.

Freshly isolated porcine retinal endothelial cells were seeded into permeable cell culture inserts. At confluency growth medium was exchanged for assay medium (1% serum). After 24 hours the endothelial cell monolayer was incubated with VEGF and / or Ang-2 in varying doses (VEGF 10-100 ng/ml; Ang-2 4-75 ng/ml). Leakage was determined at different time points using a fluorescent dextran (70 kD).

Both Ang-2 and VEGF led to an increased permeability in retinal endothelial cells. Both effects were dose-dependant. Whereas Ang-2 alone only led to a mild increase in permeability (50% increase compared to untreated cells), VEGF alone showed a stronger effect (up to 100% increase in permeability). The most evident increase in permeability was seen after treatment with Ang-2 + VEGF (300% increase in permeability compared to untreated cells). A time dependency of permeability was detected after application of the growth factors.

Both Ang-2 and VEGF increase leakage of retinal endothelial cells dose dependently. VEGF alone has twice the effect of Ang-2. Both factors acting together increase permeability more than a simple addition of their single effects would suggest. The time delay seen in the effect of the growth factors may suggest a mechanism on transcriptional or translational level.