SERUM HYALURONAN AS A DISEASE MARKER

Hyaluronan is a connective tissue polysaccharide which has also been f ound in blood serum in concentrations (100 mu g/L (average 30-40 mu g/ L in middle-aged persons). The serum level is regulated by the influx of the polysaccharide from the tissues via lymph and its receptor-medi ated clearance by liver endothelial cells. Markedly high serum levels are noted in certain liver diseases, especially in patients with cirrh osis, when the clearance is impaired. In these cases serum hyaluronan can be used to follow the development of the disease. Serum hyaluronan is also a sensitive marker for impending rejection of liver transplan ts. Patients with rheumatoid arthritis constitute another major group with increased serum hyaluronan, but in this case the level varies mar kedly during the day corresponding to physical activity. There are goo d indications that in these subjects the excess hyaluronan comes from the joints, Under stringent sampling conditions of serum it should be possible to extract interesting information on the inflammatory joint process. Increased hyaluronan levels are also seen in other inflammato ry diseases and it is of special interest that high hyaluronan levels in patients with septic conditions is a sign of poor prognosis. Certai n tumours, notably Wilms' tumour and mesothelioma, produce factors whi ch activate synthesis of hyaluronan and increase its serum level. Rare hereditary diseases with disturbances of hyaluronan metabolism and el evated blood levels have also been discovered, e.g. Werner's syndrome and cutaneous hyaluronanosis. Information accumulated during the last decade regarding the metabolism of hyaluronan has made this polysaccha ride an interesting clinical marker for a number of pathological condi tions.