Hyaluronan (HA) is involved in wound healing and its biological properties depend on its molecular size. The effects of native HA and HA-12 and HA-880 saccharide fragments on human fibroblast proliferation and expression of matrix-related genes were studied. The three HA forms promoted cell adhesion and proliferation. Matrix metalloproteinase-1 and -3 mRNA were increased by all HA forms, whereas only HA-12 stimulated the expression of the tissue inhibitor of metalloproteinase 1. HA-12 enhanced type I collagen and transforming growth factor-b (TGF-b) 1 expression. Interestingly, HA-12 and native HA stimulated type III collagen and TGF-b3. HA and its fragments activated Akt and extracellular-regulated kinases 1/2 and p38. Inhibition of these signaling pathways suggested their implication in most of the effects. Only native HA activated nuclear factor-kB and activating protein 1. Use of CD44 siRNA suggests that this HA receptor is partly implicated in the effects, although it does not rule out the involvement of other receptors. Depending on its size, HA may exert differential regulation on the wound-healing process. Furthermore, the HA up-regulation of type III collagen and TGF-b3 expression suggests that it may promote a fetal-like cell environment that favors scarless healing.

Objective. To uncover the mechanism by which chondroitin sulfate (CS) enhances hyaluronan (HA) production by human osteoarthritic (OA) fibroblast-like synoviocytes (FLS).Methods. The production of HA was investigated by exposing human OA FLS to CS in the presence or absence of interleukin-1␤ (IL-1␤). HA levels were determined by enzyme-linked immunosorbent assay, and levels of messenger RNA (mRNA) for HA synthase 1 (HAS-1), HAS-2, and HAS-3 were determined by realtime polymerase chain reaction analysis. The effect of CS and IL-1␤ on signaling pathways was assessed by Western blotting. Specific inhibitors were used to determine their effects on both HA production and HAS expression. The molecular size of HA was analyzed by high-pressure liquid chromatography.Results. CS increased HA production by FLS through up-regulation of the expression of HAS1 and HAS2. This was associated with activation of ERK-1/2, p38, and Akt, although to a lesser extent. Both p38 and Akt were involved in CS-induced HA accumulation. IL-1␤ increased HA production and levels of mRNA for HAS1, HAS2, and HAS3. CS enhanced the IL-1␤-induced level of HAS2 mRNA and reduced the level of HAS3 mRNA. IL-1␤-induced activation of p38 and JNK was slightly decreased by CS, whereas that of ERK-1/2 and Akt was enhanced. More high molecular weight HA was found in CS plus IL-1␤-treated FLS than in FLS treated with IL-1␤ alone.Conclusion. CS stimulates the synthesis of high molecular weight HA in OA FLS through up-regulation of HAS1 and HAS2. It reduces the IL-1␤-enhanced transcription of HAS3 and increases the production of HA of large molecular sizes. These effects may be beneficial for maintaining viscosity and antiinflammatory properties in the joint.Hyaluronan (HA) is a glycosaminoglycan polymer of repeated N-acetylglucosamine ␤(1-4) glucuronic acid ␤(1-3) disaccharide units (1). It is a major component of the extracellular matrix and can attain a molecular mass of 20 ϫ 10 6 daltons (2). It traps a large amount of water, giving rise to solutions of high viscosity and elasticity (3). HA participates in tissue remodeling, normal tissue homeostasis, and disease, including osteoarticular pathology, immune and inflammatory disorders, pulmonary and vascular diseases, and cancer (4,5). In joints, fibroblast-like synoviocytes (FLS) are the main source of HA. Its concentration in the synovial fluid is ϳ3 gm/liter, providing most of the properties of synovial fluid (6) and protecting cartilage from overload peaks (7). The molecular weight of synovial fluid HA is ϳ6 ϫ 10 6 daltons (8,9).In osteoarthritis (OA) synovial fluid, both the concentration and size of HA are reduced, possibly by the release of reactive oxygen species and enzymes (10).

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