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Factors in plasma and platelets do not fully account for the proliferation of smooth muscle cells in vascular injury, implying that additional factors are involved. Recently, we and others have observed that vascular injury regulates basic fibroblast growth factor, suggesting a further role for this pleiotropic factor. We report here that injury of rat arteries leads to an increase in fibroblast growth factor receptors in vascular smooth muscle cells. This up-regulation makes smooth muscle cells susceptible, in vitro and in vivo, to the lethal effects of a conjugate of basic fibroblast growth factor with the ribosome inactivator saporin. Saporin alone has no effect, whereas the conjugate kills proliferating, but not quiescent, smooth muscle cells in vitro. In vivo, one to three doses inhibit neointimal proliferation but have no apparent effect on the uninjured artery. Thus, the up-regulation of fibroblast growth factor receptors in vascular injury suggests new therapeutic possibilities for such refractory conditions as restenosis following balloon angioplasty.

Bovine aortic and corneal endothelial cells synthesize a growth factor that remains mostly cell-associated but can also be extracted from the subendothelial extracellular matrix (ECM) deposited by these cells. The endothelial cell-derived growth factors extracted from cell lysates and from the extracellular matrix appear to be structurally related to basic fibroblast growth factor by the criteria that they bind to heparin-Sepharose and are eluted at 1.4-1.6 M NaCl, have a molecular weight of about 18,400, cross-react with anti-basic fibroblast growth factor antibodies when analyzed by electrophoretic blotting and immunoprecipitation, and are potent mitogens for bovine aortic and capillary endothelial cells. It is suggested that endothelium can store growth factors capable of autocrine growth promotion in two ways: by sequestering growth factor within the cell and by incorporating it into the underlying extracellular matrix.

A human hepatoma cell line synthesizes, as evidenced by metabolic labeling, an endothelial cell mitogen that is found to be mostly cell associated. The hepatoma-derived growth factor (HDGF) has been purified to homogeneity by a combination of Bio-Rex 70, heparin-Sepharose, and reverse-phase chromatography; it is a cationic polypeptide with a molecular weight of about 18,500-19,000. HDGF is structurally related to basic fibroblast growth factor (FGF). Immunological analysis demonstrates that antiserum prepared against a synthetic peptide corresponding to the amino-terminal sequence of basic FGF cross-reacts with HDGF when analyzed by electrophoretic blotting and by immunoprecipitation. Sequence analysis of tryptic fragments demonstrates that HDGF contains sequences that are homologous to both amino-terminal and carboxyl-terminal sequences of basic FGF.

Basic fibroblast growth factor (FGF) was purified by heparin-Sepharose chromatography from two sources, brain and hepatoma cells. Brain cell-derived basic FGF (brFGF) and hepatoma cell-derived basic FGF (heFGF) were found to exist in multiple forms whose molecular weights depended on whether they were extracted from their respective tissue or cells at neutral or acid pH. When extracted at pH 7.0 brFGF and heFGF comigrated on NaDodSO4/PAGE with a Mr of approximately 18,400. When extracted at pHs 3.5-4.5, acid proteinases cleaved brFGF and heFGF to lower molecular weight forms but to different extents. brFGF was cleaved to a Mr 18,000 form at acid pH by a brain-derived acid proteinase that could be inhibited by pepstatin. heFGF was cleaved mostly to a Mr 16,500 form at acid pH by a hepatoma cell-derived acid proteinase that was inhibited by leupeptin. Electrophoretic transfer blot analysis using site-specific anti-FGF antibodies suggested that the cleavages occurred at the amino-terminal ends of brFGF and heFGF. Cleavage to lower molecular weight forms of brFGF and heFGF did not affect growth factor activity or chromatographic behavior on heparin-Sepharose columns.