Angiogenic response of endothelial cells to heparin-binding domain of fibronectin

Interaction of endothelial cells with cell-binding domain of fibronectin through integrin receptors is important in the process of angiogenesis. The present study was designed to examine the role of heparin-binding domain of fibronectin in angiogenesis using human umbilical vein endothelial cells. Attachment of endothelial cells in vitro to heparin-binding domain of fibronectin was inhibited by heparin. Chick chorioallantoic membrane assay revealed the proangiogenic nature of heparin-binding domain. Analysis by reverse transcription-polymerase chain reaction showed an increase in the expression of vascular endothelial growth factor and its receptor mRNA. Enzyme-linked immunosorbent assay showed a significant increase in the level of vascular endothelial growth factor secreted by cells maintained on heparin-binding domain. Treatment with calphostin C, an inhibitor of protein kinase C, decreased the expression of vascular endothelial growth factor receptor 2. Chick chorioallantoic membrane assay showed that the vascular endothelial growth factor secreted by cells maintained on heparin-binding domain was biologically more active, which appeared to be due to a decrease in its poly-adenosine diphosphate ribosylation. Binding assays showed that heparin-binding domain preferably binds unmodified vascular endothelial growth factor as compared to intact fibronectin. It is concluded that the heparin-binding domain of fibronectin by itself can promote angiogenesis in endothelial cells possibly by interaction with cell surface heparan sulphate proteoglycans involving protein kinase C dependent signaling and making available more active form of vascular endothelial growth factor to the cells.