Vascular smooth muscle cell growth‐promoting factor/F‐spondin inhibits angiogenesis via the blockade of integrin αvβ3 on vascular endothelial cells

Vascular smooth muscle cell growth‐promoting factor (VSGP) was originally isolated from bovine ovarian follicular fluid as a stimulator of vascular smooth muscle cell proliferation. Homology searches indicate that bovine and human VSGPs are orthologs of rat F‐spondin. Here, we examined whether recombinant human VSGP/F‐spondin affected the biological activities of endothelial cells. VSGP/F‐spondin did not affect the proliferation of human umbilical vein endothelial cells (HUVECs); however, it did inhibit VEGF‐ or bFGF‐stimulated HUVEC migration. To clarify the mechanism of this inhibitory effect, we examined the adhesion of HUVECs to extracellular matrix proteins. VSGP/F‐spondin specifically inhibited the spreading of HUVECs on vitronectin via the functional blockade of integrin αvβ3. As a result, VSGP/F‐spondin inhibited the tyrosine phosphorylation of focal adhesion kinase (FAK) when HUVECs were plated on vitronectin. Moreover, VSGP/F‐spondin inhibited the activation of Akt when HUVECs on vitronectin were stimulated with VEGF. VSGP/F‐spondin inhibited tube formation by HUVECs in vitro and neovascularization in the rat cornea in vivo. These results indicate that VSGP/F‐spondin inhibits angiogenesis at least in part by the blockade of endothelial integrin αvβ3. © 2001 Wiley‐Liss, Inc.