Synovium, rheumatoid synovial fluid

In 1943 E. A. Balazs and L. Filler published a paper in which they described a study of role of hyaluronan in dog knee joints. They found that the intercellular substance of connective tissue of the synovium contains sufficient viscous mucin that can replace the mucin removed from the knee [5]. These observations literally opened the door to further studies on the role of hyaluronan in normal and traumatic joints. In 1949, C. Ragan and K. Mayer published a very important paper in which they described the observation of hyaluronan in rheumatoid synovial fluid. This was the first study in which normal and pathological synovial fluids were compared by determination of the concentration and viscosity of hyaluronan [6]. 

Articulated joints between bones, for example at the knee, are covered in a capsule enclosing a space, which contains synovial fluid. The lining of the capsule is composed by the synovial membrane it is this synovium that becomes inflamed in rheumatoid arthritis (RA). Secretions produced by inflammatory cells (lymphocytes, macrophages... 

In rheumatoid arthritis, immune complexes are deposited in the affected joints, causing an inflammatory response that is amplified by eicosanoids. Lymphocytes and macrophages accumulate in the synovium, whereas leukocytes localize mainly in the synovial fluid. The major eicosanoids produced by leukocytes are leukotrienes, which facilitate T-cell proliferation and act as chemoattractants. Human macrophages synthesize the COX products PGE2 and TXA2 and large amounts of leukotrienes. 

Rheumatoid arthritis is a systemic autoimmune disorder produced by an inflammatory response of the synovium of the joints and is accompanied by hyperplasia of synovial cells, excess of synovial fluid, and apparition of fibrous tissue in the synovium, leading together to the destruction of the articular cartilage and ankylosis or fusion of the joints. In a pilot study published... 

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