In recent years, anti-angiogenic therapy has become an effective strategy for inhibiting tumor growth. Fucoidan is a class of fucose-enriched sulfated polysaccharides found in brown algae, and it is known to have strong anti-tumor property. Using a human umbilical vein endothelial cells (HUVEC)-based cell culture model, the present study investigated the anti-angiogenic activity of fucoidan extracted from the brown seaweed Undaria pinnatifida. Treatment of HUVECs with various concentrations of fucoidan resulted in significant inhibition of cell proliferation, cell migration, tube formation and vascular network formation. However, significant inhibition of cell proliferation only occurred with longer treatment time (48 h instead of 24h or less). About 40% of cell proliferation and cell migration and 61% of tube formation by HUVECs were inhibited by 400 μg/ml fucoidan, the maximum concentration tested. These results appeared to suggest that modulation of angiogenesis by fucoidan might not occur through growth inhibition and apoptosis. Ex vivo angiogenesis assay demonstrated that at 100 μg/ml, fucoidan caused significant reduction in microvessel outgrowth. Western blot and RT-PCR analyses indicated that at 400 μg/ml, fucoidan significantly reduced the expression of the angiogenesis factor VEGF-A in the suppression of angiogenesis activity. Our results showed that fucoidan isolated from U. pinnatifida may have a new therapeutic potential in the prevention angiogenesis-related diseases.
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