From the CRRET laboratory, CNRS ERL 9215, University of Paris-Est Créteil (UPEC), France (M.C., M.D., G.C., C.H., M.P., F.R., B.V., M.-E.G., D.V., J.C., I.C.).
Quinze Vingts National Ophthalmology Hospital, Paris, France (M.P.).
Arterioscler Thromb Vasc Biol. 2019 Sep;39(9):1843-1858. doi: 10.1161/ATVBAHA.119.313021. Epub 2019 Jul 18.
Objective Weibel-Palade bodies (WPBs) are endothelial cell (EC)-specific organelles formed by vWF (von Willebrand factor) polymerization and that contain the proangiogenic factor Ang-2 (angiopoietin-2). WPB exocytosis has been shown to be implicated for vascular repair and inflammatory responses. Here, we investigate the role of WPBs during angiogenesis and vessel stabilization. Approach and Results WPB density in ECs decreased at the angiogenic front of retinal vascular network during development and neovascularization compared with stable vessels. In vitro, VEGF (vascular endothelial growth factor) induced a VEGFR-2 (vascular endothelial growth factor receptor-2)-dependent exocytosis of WPBs that contain Ang-2 and consequently the secretion of vWF and Ang-2. Blocking VEGF-dependant WPB exocytosis and Ang-2 secretion promoted pericyte migration toward ECs. Pericyte migration was inhibited by adding recombinant Ang-2 or by silencing Ang-1 (angiopoietin-1) or Tie2 (angiopoietin-1 receptor) in pericytes. Consistently, in vivo anti-VEGF treatment induced accumulation of WPBs in retinal vessels because of the inhibition of WPB exocytosis and promoted the increase of pericyte coverage of retinal vessels during angiogenesis. In tumor angiogenesis, depletion of WPBs in vWF knockout tumor-bearing mice promoted an increase of tumor angiogenesis and a decrease of pericyte coverage of tumor vessels. By another approach, normalized tumor vessels had higher WPB density. Conclusions We demonstrate that WPB exocytosis and Ang-2 secretion are regulated during angiogenesis to limit pericyte coverage of remodeling vessels by disrupting Ang-1/Tie2 autocrine signaling in pericytes.
目的 Weibel-Palade 小体（WPB）是由 vWF（血管性血友病因子）聚合形成的内皮细胞（EC）特异性细胞器，其中包含促血管生成因子 Ang-2（血管生成素-2）。WPB 的胞吐作用被认为与血管修复和炎症反应有关。在这里，我们研究了 WPB 在血管生成和血管稳定中的作用。
方法和结果 在视网膜血管网络发育和新生血管形成过程中，与稳定血管相比，EC 中的 WPB 密度在血管生成前沿处降低。在体外，VEGF（血管内皮生长因子）诱导依赖 VEGFR-2（血管内皮生长因子受体-2）的 WPB 胞吐作用，其中包含 Ang-2，随后 vWF 和 Ang-2 的分泌。阻断 VEGF 依赖的 WPB 胞吐作用和 Ang-2 分泌促进了周细胞向 EC 的迁移。添加重组 Ang-2 或在周细胞中沉默 Ang-1（血管生成素-1）或 Tie2（血管生成素-1 受体）可抑制周细胞的迁移。一致地，体内抗 VEGF 治疗由于 WPB 胞吐作用的抑制而导致视网膜血管中 WPB 的积累，并促进血管生成过程中周细胞对视网膜血管的覆盖增加。在肿瘤血管生成中，vWF 敲除肿瘤荷瘤小鼠中 WPB 的耗竭促进了肿瘤血管生成的增加和肿瘤血管中周细胞覆盖的减少。通过另一种方法，正常化的肿瘤血管具有更高的 WPB 密度。
结论 我们证明，在血管生成过程中，WPB 的胞吐作用和 Ang-2 的分泌受到调节，通过破坏周细胞中 Ang-1/Tie2 自分泌信号，限制了周细胞对重塑血管的覆盖。
