Synoviocytes

Synovial intimal cells, termed synoviocytes, are believed to be responsible for the production of synovial fluid components for absorption from the joint cavity and for blood/synovial fluid exchanges. Two types of synoviocytes have been identified, macrophagic cells (type A cells) and fibroblast-like cells (type B cells). Type A synoviocytes are non-fixed cells that can phagocytose cell debris and wastes in the joint cavity, and have the ability to present antigens. These type A cells, derived from blood-borne monocytes, can be regarded as resident macrophages (tissue macrophages) like hepatic Kupffer cells. Type B synoviocytes are characterized by the abundant existence of rough endoplasmic reticulum, and the formation of a regular network in the luminal surface of the synovial membrane. The type B cells, which are the predominant cell type comprising the structure of the synovial intima, are involved in production of specialized matrix components, including hyaluronan, collagens and fibronectin for the intimal interstitium and synovial fluid.

Synoviocytes provide new insights into synovial tissue organization and morphogenesis, and are potential therapeutic target. These cells can be used as a good in vitro model for studying the pathogenesis of chronic inflammatory diseases, such as rheumatoid arthritis.