Heparan sulfate interacting protein (HIP/L29) negatively regulates growth responses to basic fibroblast growth factor in gingival fibroblasts

Basic fibroblast growth factor (bFGF) modulates gingival growth, and its release from heparan sulfate (HS) in the extracellular matrix (ECM) governs local tissue bioavailability. We identified a heparin/HS interacting protein (HIP/L29) that recognizes specific HS sequences. We hypothesize that HIP/L29, by modulating the interactions of bFGF with HS chains on proteoglycans, could regulate bFGF bioavailability. To investigate interactions between bFGF and HIP/L29, we isolated and cultured fibroblasts from normal gingiva and overgrown gingiva from patients on cyclosporine (CSA). bFGF significantly stimulated gingival fibroblast proliferation with or without heparin. Recombinant human HIP/L29 dramatically decreased bFGF-induced proliferation, but did not alter responses to insulin-like growth factor-1 (IGF-1). Analysis of mitogen-activated protein kinase (MAPK) phosphorylation patterns showed that bFGF stimulation of p44 (Erk-1), but not p42 (Erk-2), also was inhibited by HIP/L29 in a dose-dependent manner. Together, these results support our hypothesis that HIP/L29 modulates the bioavailability and action of bFGF.