Hall Heike, Hubbell Jeffrey A
Institute for Biomedical Engineering and Department of Materials, Federal Institute of Technology and University of Zurich, Zurich, Switzerland.
Microvasc Res. 2004 Nov;68(3):169-78. doi: 10.1016/j.mvr.2004.07.001.
Angiogenic signals can be matrix attached or freely diffusible. Here, the sixth Ig-like domain of L1 (L1Ig6), a ligand for alphavbeta3-integrin, was investigated. This domain was expressed as a fusion protein having a substrate sequence for factor XIII to enable covalent binding into three-dimensional fibrin matrices. Matrix-bound L1Ig6 induced endothelial cell (EC) process extension in vitro, which was associated with ligation and phosphorylation of alphavbeta3-integrin. VEGF-R2 and alphavbeta3 were observed to co-associate after stimulation with either L1Ig6 or VEGF-A165, whereas no co-association with bFGF-R was observed. Furthermore, VEGF-R2 was tyrosine phosphorylated after stimulation with L1Ig6, even in the absence of exogenous VEGF-A165, indicating close cooperation between VEGF-R2 and alphavbeta3. Angiogenesis was investigated in vivo by stimulating chicken chorioallantoic membranes (CAMs) with L1Ig6-modified matrices with or without co-incorporation of VEGF-A165 or bFGF. Matrix-immobilized L1Ig6 induced angiogenesis to a similar degree as VEGF-A165; co-stimulation with bFGF increased vascular branching, whereas VEGF-A165 did not. Matrix-immobilized L1Ig6 induced up-regulation of alphav in CAMs by a similar degree as stimulation with VEGF-A165, and this up-regulation was increased further by co-stimulation with matrix-bound L1Ig6 and VEGF-A165. alpha5 and beta1 levels were not increased. The similarity of action of matrix-bound L1Ig6 and soluble VEGF-A165 indicate a close link between specific ligation of alphavbeta3-integrin and VEGF-R2 and suggest the possible use of matrix-bound L1Ig6 in local therapeutic angiogenesis.
血管生成信号可以是附着于基质的，也可以是自由扩散的。在此，对αvβ3整合素的配体L1的第六个免疫球蛋白样结构域（L1Ig6）进行了研究。该结构域表达为一种具有因子XIII底物序列的融合蛋白，以便能够共价结合到三维纤维蛋白基质中。结合在基质上的L1Ig6在体外诱导内皮细胞（EC）的突起延伸，这与αvβ3整合素的连接和磷酸化有关。在用L1Ig6或VEGF-A165刺激后，观察到VEGF-R2和αvβ3共同结合，而未观察到与bFGF-R的共同结合。此外，即使在没有外源性VEGF-A165的情况下，用L1Ig6刺激后VEGF-R2也会发生酪氨酸磷酸化，这表明VEGF-R2和αvβ3之间存在密切合作。通过用L1Ig6修饰的基质刺激鸡绒毛尿囊膜（CAMs），在有或没有同时加入VEGF-A165或bFGF的情况下，在体内研究血管生成。固定在基质上的L1Ig6诱导血管生成的程度与VEGF-A165相似；与bFGF共同刺激增加了血管分支，而VEGF-A165则没有。固定在基质上的L1Ig6诱导CAMs中αv的上调程度与用VEGF-A165刺激相似，并且通过与结合在基质上的L1Ig6和VEGF-A165共同刺激，这种上调进一步增加。α5和β1水平没有增加。结合在基质上的L1Ig6和可溶性VEGF-A165作用的相似性表明αvβ3整合素与VEGF-R2的特异性连接之间存在密切联系，并提示结合在基质上的L1Ig在局部治疗性血管生成中的可能用途。
