Structural features in heparin which modulate specific biological activities mediated by basic fibroblast growth factor

Abstract

The biological activity of basic fibroblast growth factor (bFGF) is influenced greatly by direct binding to heparin and heparan sulphate (HS). Heparin-derived oligosaccharides have been utilized to determine the structural requirements present in the polymer that account for binding to bFGF. We had previously demonstrated that fragments > 6 mer can inhibit the interaction between cell surface heparan sulphate proteoglycan (HSPG) and bFGF, and bFGF-induced proliferation of adrenocortical endothelial (ACE) cells. In contrast, oligosaccharides > 10 mer can enhance the binding of bFGF to its high-affinity receptor or support bFGF-induced mitogenesis in ACE cells (Ishihara et al., J. Biol. Chem., 268, 4675-4683, 1993). We have extended these studies to size- and structure-defined oligosaccharides from heparin, 2-O-desulphated (2-O-DS-) heparin, 6-O-desulphated (6-O-DS-) heparin, carboxy-reduced (CR-) heparin and carboxy-amidomethylsulphonated (AMS-) heparin. Oligosaccharides from these polymers were fractionated on a bFGF-affinity column and were assessed as inhibitors or enhancers of specific bFGF-derived biological activities. The results of these studies indicate that both 2-O-sulphate and the negative charge of the carboxy group [L-iduronic acid (IdoA) residues] are required for specific interactions of heparin-derived oligosaccharides with bFGF and for modulation of bFGF mitogenic activity. In addition, the charge of the carboxy groups in uronic acids can be replaced by other functional groups with a negative charge, such as the amidomethyl sulphonate moiety described here.

Heparin oligosaccharides: inhibitors of the biological activity of bFGF on Caco-2 cells

“…The results show that 85% of the disaccharides are the trisulphated disaccharide IdoA(2S)-GlcNS(6S) and that 95% of all disaccharides contain GlcNS and IdoA(2S), sulphated moieties implicated in the interaction between bFGF and heparan sulphate (Turnbull et al, 1992;Ishihara et al, 1994;Maccarana et al, 1993). These data suggest that oligosaccharides derived from bovine lung heparin will be quite homogeneous in composition and that the biological activity of oligosaccharides will result from differences in length rather than composition.…”

“…An oligosaccharide could interfere with any of these processes by occupying HS binding sites on bFGF, preventing the access of functional HS to the molecule. Although less sulphated oligosaccharides would have greater specificity for a heparin-binding growth factor (Hahnenberger et al, 1993;Maccarana et al, 1993;Ishihara, 1994;Ishihara et al, 1994), from the clinical standpoint bovine lung heparin oligosaccharides are attractive anti-growth factor agents, as their structure encompasses features required for the binding of HGF (Lyon et al, 1994b) as well as other members of the FGF family (Guimond et al, 1993;Ishihara, 1994). Thus, an inhibitory oligosaccharide derived from bovine lung heparin may have the capacity to inhibit at least four growth factors (HGF, personal communication from M Lyon, JA Deakin and JT Gallagher) that have been implicated in cancer biology, and we are investigating this.…”

“…Each of these disaccharide units contains the sulphate groups that have been implicated in the binding and activation of bFGF, namely the N-sulphate on glucosamine and the 2-0-sulphate on iduronic acid. The 6-0-sulphate is not thought to be important to the interaction between HS and bFGF (Coltrini et al, 1994;Ishihara et al, 1994), although it has been implicated in the interaction between HS and the FGF receptor (Guimond et al, 1993).…”

Synergism between Wnt3a and Heparin Enhances Osteogenesis via a Phosphoinositide 3-Kinase/Akt/RUNX2 Pathway

“…Cells transfected with the empty vector pcDNA3.1 (-) were used as negative control. Cells were re-plated at 24 h post-transfection at a density of 2500 cells/cm 2 and then treated for 72 h with 50 ng/ml Wnt3a and/or between 0.5-50 g/ml heparin as indicated before harvesting.…”

“…Heparin-growth factor interactions control the activities of susceptible ligands and in particular their interactions with cognate receptors, so dictating mesenchymal lineage progression and cell behavior. Heparin (and the less sulfated heparan sulfates) facilitates the binding of FGF2 to FGFRs, so augmenting osteoblast proliferation and differentiation (1)(2)(3)(4)(5). These GAGs also enhance the activity of BMPs, osteoinductive growth factors that have been clinically approved for spinal fusion, in part by protecting them from enzymatic attack or structural antagonists (6,7).…”