Vascular endothelial growth factor (VEGF) stimulates monocyte migration through endothelial monolayers via increased integrin expression

Monocytes play an important role in collateral vessel formation (arteriogen esis) by attaching to activated endothelium and by invading the walls of in nate collateral vessels where they produce growth factors. Previous studies have demonstrated that this process fan be promoted by several chemokines and growth factors. In this study we examined the interaction between monoc ytes and endothelium under stimulation of the angiogenic agent vascular end othelial growth factor (VEGF). We report here the novel finding that VEGF s timulates the expression of the alpha (L)-, alpha (M)- and beta (2)-integri n monomers. In functional assays and by using neutralizing antibodies it wa s shown that VEGF stimulates adhesion of monocytes to human umbilical vein endothelial cells (HUVEC), and increased transmigration through endothelial monolayers is dependent on interaction of monocyte B-2-integrins with its endothelial counter ligand ICAM-1. Based on these in vitro data we hypothes ize that the positive effect of VEGF on arteriogenesis may involve monocyte activation.