Chondroitin sulfate increases hyaluronan production by human synoviocytes through differential regulation of hyaluronan synthases: Role of p38 and Akt

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‐1β (IL‐1β). 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 real‐time polymerase chain reaction analysis. The effect of CS and IL‐1β 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‐1β increased HA production and levels of mRNA for HAS1, HAS2, and HAS3. CS enhanced the IL‐1β–induced level of HAS2 mRNA and reduced the level of HAS3 mRNA. IL‐1β–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‐1β–treated FLS than in FLS treated with IL‐1β 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‐1β–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.