To determine if preexposure of human articular cartilage to activated neutrophils alters rheumatoid synovial fibroblast adhesion to human articular cartilage.
Human articular cartilage was exposed to either activated neutrophils, interleukin-1, or supernatants obtained from activated neutrophils that had been treated with different protease inhibitors. Radiolabeled rheumatoid synovial fibroblasts were then incubated with the cartilage and the number of counts associated with the cartilage was determined.
Pretreatment of human articular cartilage with either activated neutrophils or supernatants obtained from activated neutrophils enhanced subsequent rheumatoid synovial fibroblast adhesion. In contrast, interleukin-1 treatment of cartilage did not alter the adhesion of synovial fibroblasts. The enhanced adhesion could be attenuated by pretreatment of the neutrophil supernatants with either diisopropylfluorophosphonate or EGTA and almost completely abolished by using both inhibitors.
This study demonstrates that adhesion of rheumatoid synovial fibroblasts to human articular cartilage can be enhanced by exposing the cartilage to proteases released by neutrophils. These results suggest that neutrophil products may play a role in enhancing adhesion of rheumatoid synovium to cartilage in vivo.