Poly(ethylene glycol acrylate)-functionalized hydrogels for heparan sulfate oligosaccharide recognition.

Heparan sulfates are complex polysaccharides belonging to the family of glycosaminoglycans that participate to the regulation of cell behavior and tissue homeostasis. The biological activities conferred to heparan sulfates are largely dependent on the content and positioning of the sulfate groups along their saccharidic units. At present, identification of particular sulfation patterns in biologically relevant heparan sulfate sequences remains challenging. Although several approaches for structure analysis exist, the complexity of heparan sulfates makes new and original approaches still required. Here, we used molecular imprinting technologies to prepare a library of polyethylene glycol acrylate functionalized hydrogels with the aim to investigate their applicability as specific recognizing systems for fondaparinux, a synthetic pentasaccharide analog to the antithrombin binding site of heparin. Adequate choice of the hydrogel composition and controlling rebinding conditions were important determinants for improving the sulfated oligosaccharide recognition specificity and selectivity. Our results suggest that molecular imprinting approaches could be a possibility for the specific recognition of biologically active sequences in heparan sulfates.

Molecular imprinting technology for specific recognition of heparan sulfate like disaccharides.

Iinteractions of biologically active proteins with sulfated glycans, particularly heparan sulfates (HS), are dependent on factors involving amounts and positions of the sulfate groups in the sugars chains. Although the importance of knowing the exact positions of the sulfate groups in particular HS sequences is well recognized, at present, approaches in this area are complex and still considered as a challenge. Here, we investigated the applicability of the 'Molecular Imprinting Technology' for the generation of imprinted polymers able to specifically recognize a model HS-like disaccharide. In order to advance on the applicability of this technology to the recognition of these complex sugars, we prepared a library of imprinted polymers to investigate the impact of the polymerization reaction conditions and stoichiometry on the generation of binding sites able to specifically recognize the model sulfated sugar. Our results show that imprinted polymers able to specifically bind HS-like saccharide can readily be obtained. This constitutes a suitable option for developing novel strategies directed to study fine sulfated sugars structures.

Glycosaminoglycan mimetics trigger IP3-dependent intracellular calcium release in myoblasts.

Glycosaminoglycans (GAG) are sulfated polysaccharides that play an important role in regulating cell functions. GAG mimetics called RGTAs (for ReGeneraTing Agents) have been shown to stimulate tissue repair. In particular they accelerate myogenesis, in part via their heparin-mimetic property towards growth factors. RGTAs also increase activity of calcium-dependent intracellular protease suggesting an effect on calcium cellular homeostasis. This effect was presently investigated on myoblasts in vitro using one member of the RGTA family molecule named OTR4120. We have shown that OTR4120 or heparin induced transient increases of intracellular calcium concentration ([Ca(2+)]i) in pre-fusing myoblasts from both mouse SolD7 cell line and rat skeletal muscle satellite cells grown in primary culture by mobilising sarcoplasmic reticulum store. This [Ca(2+)]i was not mediated by ryanodine receptors but instead resulted from stimulation of the Inositol-3 phosphate-phospholipase C activation pathway. OTR4120-induced calcium transient was not mediated through an ATP, nor a tyrosine kinase, nor an acetylcholine receptor but principally through serotonin 5-HT2A receptor. This original finding shows that the GAG mimetic can induce calcium signal through serotonin receptors and the IP3 pathway may be relevant to its ability to favour myoblast differentiation. It supports a novel and unexpected function of GAGs in the regulation of calcium homeostasis.