Changes in hyaluronan concentration in tissues and body fluids in disease states.

Proteins which specifically bind hyaluronan have been used to develop sensitive immunoassay-like analytical techniques. These assays have made it possible to analyse hyaluronan concentrations in nanogram amounts in tissues and body fluids. The normal adult human circulating level of hyaluronan varies between 10 and 100 micrograms/l. Increased levels of serum hyaluronan (greater than 1 mg/l) have been found in inflammatory rheumatic diseases such as rheumatoid arthritis, scleroderma and psoriatic arthritis. Even higher levels occur in serum from patients with cirrhotic liver diseases and in patients with malignant mesothelioma. Elevated serum hyaluronan levels are a sign either of increased production and/or outflow from the tissues or of decreased elimination of the polysaccharide in the liver endothelial cells or in other parts of the reticuloendothelial system or through the kidneys. The serum concentration is also influenced by increased age and by the degree of physical activity. Important information on pathological processes has been gained by analysing the hyaluronan concentration in other body fluids such as urine, perfusion fluid from the intestine and bronchoalveolar lavage fluid. In the future these analyses should also be useful in clinical work.