A collagen Vα1-derived fragment inhibits FGF-2 induced-angiogenesis by modulating endothelial cells plasticity through its heparin-binding site

•HEPV is a colvα1-derived fragment that shows high affinity for heparin and heparin sulphate.•HEPV binds to FGF2 and represses angiogenesis induced by FGF2 but not VEGF-A.•The heparin binding site of HEPV is required for in vitro and in vivo anti-angiogenic activity.•HEPV abrogates the ability of endothelial cells to form sprouts in 3D gels.•HEPV inhibits FGF2-induced angiogenesis by eliciting EndoMT in vivo. Type V collagen (ColV) is a component of the endothelial basement membrane zone. During angiogenesis, extracellular matrix remodelling results in the release of active protein fragments that display pro- or anti-angiogenic properties. The latter often exert their activity through their heparin-binding site. We previously characterized a ColVα1-derived fragment called HEPV that contains a high affinity-binding site for heparin and heparan sulphate chains. Here we show that HEPV binds to FGF2 through its heparin-binding site. Using in vitro and in vivo angiogenesis assays, we show that HEPV but not the HEPV mutant at the heparin-binding site, inhibits FGF2-dependant angiogenesis. On the opposite, HEPV does not bind to VEGFA and has no effect on VEGFA-mediated angiogenesis. In 3D collagen gels, the addition of HEPV abrogates endothelial cell invasion and sprouting induced by FGF2. Interestingly, in vivo experiments reveal that HEPV anti-angiogenic activity is associated with the appearance of endothelial to mesenchymal transition (EndMT) markers. Together, these findings indicate that the ColVα1-derived fragment HEPV functions as an anti-angiogenic factor that represses FGF2-mediated angiogenesis through the regulation of endothelial cell plasticity. Previous observations showing that ColV overexpression negatively regulates pathological angiogenesis were left unexplained. Our data provide insights into the possible molecular mechanisms.