Effects of interleukin-1 beta and tumor necrosis factor-alpha on expression of matrix-related genes by cultured equine articular chondrocytes

Objective-To determine the effects of interleukin-1 beta (IL-1 beta) and tu mor necrosis factor-alpha. (TNF-alpha) on expression and regulation of seve ral matrix-related genes by equine articular chondrocytes. Sample Population-Articular cartilage harvested from grossly normal joints of 8 foals, 6 yearling horses, and 8 adult horses. Procedure-Chondrocytes maintained in suspension cultures were treated with various doses of human recombinant IL-1 beta or TNF-alpha. Northern blots o f total RNA from untreated and treated chondrocytes were probed with equine complementary DNA (cDNA) probes for cartilage matrix-related genes. incorp oration of S-35-sulfate, fluorography of C-14-proline labeled medium, zymog raphy, and western blotting were used to confirm effects on protein synthes is. Results-IL-1 beta and TNF-alpha increased steady-state amounts of mRNA of m atrix metalloproteinases 1, 3, and 13 by up to 100-fold. Amount of mRNA of tissue inhibitor of metalloproteinase-1 also increased but to a lesser exte nt (1.5- to 2-fold). Amounts of mRNA of type-II collagen and link protein w ere consistently decreased in a dose-dependent manner. Amount of aggrecan m RNA was decreased slightly; amounts of biglycan and decorin mRNA were minim ally affected. Conclusions and Clinical Relevance-Treatment of cultured equine chondrocyte s with IL-1 beta or TNF-alpha resulted in marked alterations in expression of various matrix and matrix-related genes consistent with the implicated i nvolvement of these genes in arthritis. Expression of matrix metalloprotein ases was increased far more than expression of their putative endogenous in hibitor. Results support the suggestion that IL-1 beta and TNF-alpha play a role in the degradation of articular cartilage in arthritis.