Objective: Previous studies have reported elevated levels of interleukin-1 (IL-1) and oncostatin M (OSM) in rheumatoid joints, as well as the synergistic degradation of human articular cartilage by this cytokine combination. The present study was undertaken to investigate the ability of IL-1 and OSM to modulate gene expression of matrix metalloproteinase (MMP), ADAM, and ADAM-TS (ADAM with thrombospondin motifs) family members in human chondrocytes.

Methods: T/C28a4 human chondrocytes were stimulated for 2-48 hours with IL-1 and/or OSM. Total RNA was harvested, reverse transcribed, and assessed by real-time polymerase chain reaction for the expression of various MMP, ADAM, and ADAM-TS messenger RNAs (mRNA). Results were normalized to 18S ribosomal RNA.

Results: IL-1 and OSM synergized to markedly induce the expression of the collagenases MMP-1, MMP-8, and MMP-13 as well as MMP-3, an activator of proMMPs. Expression of mRNA for MMPs 1, 3, and 13 was induced early, whereas that of MMP-8 mRNA occurred late. Gene expression of MMP-14, an MMP that degrades collagen and activates proMMP-13, was elevated by this combination. IL-1 and OSM also synergized to induce gene expression of the aggrecanase ADAM-TS4, but not ADAM-TS5.

Conclusion: These data indicate that the potent cartilage-degrading properties of the combination of IL-1 and OSM are potentially mediated by a synergistic induction of the aggrecan-degrading enzyme ADAM-TS4 and the collagen-degrading enzymes MMP-1, MMP-8, MMP-13, and MMP-14, although differences in the magnitude of response and in the time course of induction were observed. A role for MMPs 3 and 14 in the activation of proMMPs may also be implicated.