Athanasopoulos Athanasios N, Schneider Darius, Keiper Tanja, Alt Volker, Pendurthi Usha R, Liegibel Ute M, Sommer Ulrike, Nawroth Peter P, Kasperk Christian, Chavakis Triantafyllos
Department of Internal Medicine I, University Heidelberg, D-69120 Heidelberg.
Department of Trauma Surgery, University Hospital Giessen-Marburg, D-35385 Giessen, Germany.
J Biol Chem. 2007 Sep 14;282(37):26746-26753. doi: 10.1074/jbc.M705200200. Epub 2007 Jul 10.
Angiogenesis is indispensable during fracture repair, and vascular endothelial growth factor (VEGF) is critical in this process. CCN1 (CYR61) is an extracellular matrix signaling molecule that has been implicated in neovascularization through its interactions with several endothelial integrin receptors. CCN1 has been shown to be up-regulated during the reparative phase of fracture healing; however, the role of CCN1 therein remains unclear. Here, the regulation of CCN1 expression in osteoblasts and the functional consequences thereof were studied. Stimulation of osteoblasts with VEGF resulted in a dose- and time-dependent up-regulation of CCN1 mRNA and protein. An up-regulation of both cell surface-associated CCN1 as well as extracellular matrix-associated CCN1 in osteoblasts was found. The supernatant of VEGF-prestimulated osteoblasts was chemotactic for endothelial cells, increasing their migration and stimulated capillary-like sprout formation. These effects could be attributed to the presence of CCN1 in the osteoblast supernatant as they were prevented by an antibody against CCN1 or by small interfering RNA-mediated knockdown of osteoblast CCN1. Moreover, the supernatant of VEGF-prestimulated osteoblasts induced angiogenesis in Matrigel plugs in vivo in a CCN1-dependent manner. In addition, blockade of CCN1 prevented bone fracture healing in mice. Taken together, the present work demonstrates a potential paracrine loop consisting of the VEGF-mediated up-regulation of CCN1 in osteoblasts that attracts endothelial cells and promotes angiogenesis. Such a loop could be operative during fracture healing.
血管生成在骨折修复过程中不可或缺，血管内皮生长因子（VEGF）在此过程中起关键作用。CCN1（CYR61）是一种细胞外基质信号分子，通过与几种内皮整合素受体相互作用参与新生血管形成。研究表明，CCN1在骨折愈合的修复阶段表达上调；然而，CCN1在其中的作用仍不清楚。在此，我们研究了成骨细胞中CCN1表达的调控及其功能后果。用VEGF刺激成骨细胞导致CCN1 mRNA和蛋白呈剂量和时间依赖性上调。发现成骨细胞中细胞表面相关CCN1以及细胞外基质相关CCN1均上调。VEGF预刺激的成骨细胞的上清液对内皮细胞具有趋化作用，增加其迁移并刺激毛细血管样芽的形成。这些作用可归因于成骨细胞上清液中存在CCN1，因为抗CCN1抗体或小干扰RNA介导的成骨细胞CCN1敲低可阻止这些作用。此外，VEGF预刺激的成骨细胞的上清液以CCN1依赖性方式在体内诱导基质胶塞中的血管生成。此外，阻断CCN1可阻止小鼠骨折愈合。综上所述，本研究表明存在一种潜在的旁分泌环，由VEGF介导的成骨细胞中CCN1上调组成，该上调吸引内皮细胞并促进血管生成。这样的环可能在骨折愈合过程中起作用。
