Neutrophil-mediated cartilage injury in vitro is enhanced by tumour necrosis factor alpha

Neutrophil functions relevant to tissue damage are altered by cytokines such as tumour necrosis factor alpha (cachectin, TNFα), known to be present in inflammatory foci. In this study we examined the effect of TNFα on neutrophil-mediated cartilage damage in vitro. Human neutrophils were able to injure both human and bovine articular cartilage slices by degrading proteoglycan and inhibiting its synthesis. Recombinant human TNFα enhanced neutrophil-mediated degradation of proteoglycan, even when neutrophils were preincubated with TNFα and washed before incubating with cartilage. TNFα alone degraded proteoglycan and inhibited its synthesis. Neutrophil-mediated inhibition of proteoglycan biosynthesis was increased after incubating cartilage together with neutrophils and TNFα, but was unaltered when neutrophils were preincubated with TNFα. We conclude that TNFα enhances neutrophil injury to articular cartilage.