Expression of osteopontin messenger RNA and protein in rheumatoid arthritis: Effects of osteopontin on the release of collagenase 1 from articular chondrocytes and synovial fibroblasts

Objective Osteopontin (OPN) is an extracellular matrix protein that has been implicated in the interactions between tumor cells and host matrix, including those involved in invasion and spread of tumor cells. Because joint destruction in rheumatoid arthritis (RA) is mediated by the invasive growth of synovial tissue through its attachment to cartilage, we examined the expression of OPN in the synovia of patients with RA and the effect of OPN on the production of collagenase 1 in rheumatoid synovial fibroblasts and articular chondrocytes. Methods The expression of OPN messenger RNA (mRNA) and protein in synovia from 10 RA patients was examined by in situ hybridization and immunohistochemistr…