The role of mesenchymal cells in the pathophysiology of inflammatory arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory disorder of the joints that can cause severe disability. While the role of inflammatory cells in the pathogenesis of RA has been well established, the specific contribution of resident cells within the synovial membrane, especially those of mesenchymal origin, has become the object of closer scrutiny only recently. The central position of these cells in the disease process of RA is underlined by their involvement in its main pathophysiological features: inflammation, hyperplasia and joint destruction. In this chapter, we provide a characterisation of resident mesenchymal cells, specifically fibroblast-like cells in the rheumatoid synovium, and give an overview of the molecular pathways by which these cells are involved in the initiation and perpetuation of RA.