Overexpression of a secretory form of FGF-1 promotes MMP-1-mediated endothelial cell migration

A coordinated interaction between fibroblast growth factors (FGFs) and matr ix metalloproteinases (MMPs) is implicated in migration of microvascular en dothelial cells (ECs), an early stage of angiogenesis. Specifically, we inv estigated microvascular ECs migration in vitro, which can be initiated by t he overexpression of a secretory form of the angiogenic fibroblast growth f actor-1 (FGF-1) and mediated through the enzymatic activity of matrix metal loproteinase-l (MMP-1). MMP-1 is a member of the MMP family with a propensi ty for degradation of interstitial type I collagen. We stably overexpressed a chimeric FGF-1 construct composed of the FGF-4 signal-peptide gene, link ed in-frame to the FGF-1 coding frame gene (sp-FGF-1), in cultured postcapi llary venular ECs. The presence of the biologically active form of FGF-1 wa s readily detected in the conditioned medium of ECs transfected with sp-FGF -l construct as demonstrated by DNA synthesis assay. The sp-FGF-1-, but not the plasmid vector alone-transfected ECs, exhibited an altered morphology as demonstrated by their conversion from a classic cobblestone form to a fi broblastlike shape that featured prominent neuritelike extensions. Addition of the anti-FGF receptor 1 antibody (FGFR1 Ab) reverted the transformed ph enotype of sp-FGF-l transfectants. This suggests that the resulting phenoty pic transformation in sp-FGF-l transfectants requires an uninterrupted inte raction between the FGF-1 ligand and its receptor. We studied migration of cells through matrices of either highly pure collagen I or reconstituted ba sement membrane (matrigel) and found that sp-FGF-1-transfected cells migrat ed two times and six times faster than the vector control transfectants in the respective matrices. We further demonstrated that the enhanced migratio n rate of sp-FGF-1-transfected EC coincided with the induction of their MMP -1 mRNA level and increased enzymatic activity. The enhanced migratory acti vity of sp-FGF-l could be blocked with a selective inhibitor of MMP-1. Thes e results suggest that the multipotent FGF-1 plays a key role in the early stages of angiogenesis, by mediating MMP-1 proteolytic activity. (C) 2000 W iley-Liss, Inc.