An in vitro system for studying cartilage degradation by macrophages.

Cartilage damage in inflammatory arthritis may be mediated by a number of cell types; the macrophage is one of them. To examine their role we developed a new macrophage-cartilage co-culture system on a microscale. This used macrophages derived from the peritoneal cavity of Balb/c mice together with cartilage slices from bovine nasal septa. We examined the effects of macrophages on cartilage proteoglycan loss measured colorimetrically. When chondrocytes were dead, cartilage released proteoglycan; macrophages increase the amount of proteoglycan loss; stimulating macrophages with zymosan further increased proteoglycan loss. With live chondrocytes the situation was different. Macrophages only gave a major increase in cartilage proteoglycan loss when stimulated by zymosan. These results show it is possible to establish a simple model of macrophage-induced cartilage degradation. In this a variety of effects given by macrophages can be demonstrated depending on the presence or absence of live chondrocytes.