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

Abstract

Objective - To determine the effects of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) on expression and regulation of several 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-1β or TNF-α. Northern blots of total RNA from untreated and treated chondrocytes were probed with equine complementary DNA (cDNA) probes for cartilage matrix-related genes. Incorporation of 35S-sulfate, fluorography of 14C-proline labeled medium, zymography, and western blotting were used to confirm effects on protein synthesis. Results - IL-1β and TNF-α increased steady-state amounts of mRNA of matrix 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 extent (1.5-to 2-fold). Amounts of mRNA of type-II collagen and link protein were consistently decreased in a dose-dependent manner. Amount of aggrecan mRNA was decreased slightly; amounts of biglycan and decorin mRNA were minimally affected. Conclusions and Clinical Relevance - Treatment of cultured equine chondrocytes with IL-1β or TNF-α resulted in marked alterations in expression of various matrix and matrix-related genes consistent with the implicated involvement of these genes in arthritis. Expression of matrix metalloproteinases was increased far more than expression of their putative endogenous inhibitor. Results support the suggestion that IL-1β and TNF-α play a role in the degradation of articular cartilage in arthritis.