Objective: To investigate the mechanism of the inhibitory action of hyaluronan (HA) on interleukin-1beta (IL-1beta)-stimulated production of matrix metalloproteinases (MMPs) in human articular cartilage.
Methods: IL-1beta was added to normal and osteoarthritic (OA) human articular cartilage in explant culture to stimulate MMP production. Articular cartilage was incubated or preincubated with a clinically used form of 800-kd HA to assess its effect on IL-1beta-induced MMPs. Levels of secreted MMPs 1, 3, and 13 in conditioned media were detected by immunoblotting; intracellular MMP synthesis in chondrocytes was evaluated by immunofluorescence microscopy. Penetration of HA into cartilage tissue and its binding to CD44 were analyzed by fluorescence microscopy using fluoresceinated HA. Blocking experiments with anti-CD44 antibody were performed to investigate the mechanism of action of HA.
Results: Treatment and pretreatment with 800-kd HA at 1 mg/ml resulted in significant suppression of IL-1beta-stimulated production of MMPs 1, 3, and 13 in normal and OA cartilage explant culture. Fluorescence histocytochemistry revealed that HA penetrated cartilage tissue and localized in the pericellular matrix around chondrocytes. HA-binding blocking experiments using anti-CD44 antibody demonstrated that the association of HA with chondrocytes was mediated by CD44. Preincubation with anti-CD44 antibody, which suppressed IL-1beta-stimulated MMPs, reversed the inhibitory effect of HA on MMP production that was induced by IL-1beta in normal and OA cartilage.
Conclusion: This study demonstrates that HA effectively inhibits IL-1beta-stimulated production of MMP-1, MMP-3, and MMP-13, which supports the clinical use of HA in the treatment of OA. The action of HA on IL-1beta may involve direct interaction between HA and CD44 on chondrocytes.