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.

V 型胶原蛋白 (ColV) 是内皮基底膜区的组成部分。在血管生成过程中，细胞外基质重塑导致活性蛋白片段的释放，这些片段显示出促血管生成或抗血管生成的特性。后者通常通过其肝素结合位点发挥其活性。我们之前描述了一种名为 HEPV 的 ColVα1 衍生片段，该片段包含肝素和硫酸乙酰肝素链的高亲和力结合位点。在这里我们展示了 HEPV 通过其肝素结合位点与 FGF2 结合。使用体外和体内在血管生成测定中，我们显示 HEPV 而不是肝素结合位点的 HEPV 突变体，抑制 FGF2 依赖性血管生成。相反，HEPV 不与 VEGFA 结合，对 VEGFA 介导的血管生成没有影响。在 3D 胶原凝胶中，添加 HEPV 可消除 FGF2 诱导的内皮细胞侵袭和萌芽。有趣的是，体内实验表明，HEPV 抗血管生成活性与内皮间质转化 (EndMT) 标志物的出现有关。总之，这些发现表明 ColVα1 衍生片段 HEPV 作为抗血管生成因子发挥作用，通过调节内皮细胞可塑性来抑制 FGF2 介导的血管生成。先前的观察结果表明，ColV 过表达负调节病理性血管生成，但无法解释。我们的数据提供了对可能的分子机制的见解。