Rapid degradation of articular cartilage proteoglycan by neutrophils: Comparison with macrophages and synovial fibroblasts

Abstract

Objective and design. To determine and compare the proteoglycan degradative properties of neutrophils, macrophages and synoviocytes in cultures of articular cartilage. Material of subjects. Bovine articular cartilage was aseptically isolated from metacarpopharyngeal joints. Neutrophils and macropahges were isolated from normal human blood and bovine synovial fibroblasts were isolated from explant cultures before being incubated with the cartilage. Treatment: Neutrophils, macrophages or synovial fibroblasts (1 2 106-8 2 106) were incubated with 35SO4 labelled cartilage for 2.5-72 h. Methods. Cartilage degradation was measured as a loss of 35SO4 into the cartilage medium as a percentage of the total labelled proteoglycan in the cartilage slice. Statistical significances were determined using a 2-tailed unpaired Student's t-test. Results. Neutrophils rapidly degraded articular cartilage. After 2.5 hours of culture, neutrophils degraded cartilage proteoglycan up to 28 times more than either macrophages or synovial fibroblasts. Conclusions. Neutrophils induce rapid damage to articular cartilage proteoglycan, whereas in comparison, macrophages and synovial fibroblasts degrade articular cartilage proteoglycans poorly. These findings indicate that at least under conditions where the influence of cellular-cellular interactions and soluble mediator action are excluded, adhesion of neutrophils to articular cartilage is sufficient to stimulate rapid and marked cartilage degradation compared to the other two cell types.