Modulation of endothelial sVEGFR-1 secretion by carbohydrates

Objectives: Vascular endothelial growth factor (VEGF) which is secreted by granulosa cells and its soluble receptor (sVEGFR-1) are key regulators in human ovarian angiogenesis. VEGF promotes blood vessel formation while endothelial sVEGFR-1 is an antagonist to VEGF action. Since follicular fluid surrounding the granulosa cells contains angiogenesis-regulating factors like proteoglycans or lipoproteins and is, furthermore, rich in carbohydrates, we investigated in this research project the influence of various mono- and disaccharides on sVEGFR-1 production in endothelial cells.

Methods: Endothelial cells isolated from human umbilical cord vein (HUVECs) were seeded at 100,000 cells in 24-multiwell plates. Twenty-four hours afterwards, twelve mono- and disaccharides were added at increasing amounts to the culture. Control cells were used without supplementation. After four days incubation in serumfree EBM-2 medium the amount of sVEGFR-1 was quantified in HUVEC supernatant by enzyme-linked immunosorbent assay (ELISA) and statistically analyzed.

Results: HUVECs were incubated either with 10, 50, 100, 250, 500, or 750µM mono- and disaccharides, respectively. After sVEGFR-1 quantification we distinguished five carbohydrate groups with different receptor-modulating properties. Group 1 increased sVEGFR-1 concentration in HUVEC supernatant about 1.9-fold in comparison to control cells whereas group 2 stimulated soluble VEGF receptor 1 release 1.5-fold. Group 3, however, showed no effect on endothelial receptor secretion at all. By contrast, group 4 reduced the sVEGFR-1 amount approximately by 72% in comparison to control cells while group 5 caused a reduction of 55%. Stimulating and inhibiting effects on soluble VEGF receptor 1 production by carbohydrate groups 1, 2, 4, and 5 reached all statistical significance.

Conclusion: This project reveals that selected mono- and disaccharides are able to up- and downregulate sVEGFR-1 production in endothelial cells significantly suggesting that carbohydrates thus may play a role in the modulation of human ovarian angiogenesis.