Background: A significant increase in serum hyaluronan (HA) levels has been reported in patients with liver cirrhosis. This mechanism is not yet clear, and receptors for HA have not been characterized. In this study, we examined the expression of both HA and its receptors, CD44 and intercellular adhesion molecule-1 (ICAM-1), in dimethylnitrosamine-induced liver cirrhosis.
Methods and Results: Using biotinylated HA binding protein, HA was detected in the area of periportal fibrosis and around the sinusoidal wall where hepatic fibrosis was developing. Electron microscopy revealed that HA was localized on Ito cells and sinusoidal endothelial cells (SEC). Conversely, CD44, which was only expressed weakly in normal liver, was present in large amounts in cirrhotic liver. The distribution pattern of CD44 was similar to that of HA, however, CD44 was mainly localized on the infiltrating lymphocytes and Kupffer cells. Moreover, CD44 was detected on part of factor VIII-positive SEC. intercellular adhesion molecule-1, another receptor for HA, was detected on the surface of hepatocytes and around the sinusoidal wall in cirrhotic liver, but its distribution was not accompanied by expression of HA. With respect to CD44 isoforms, the standard form m-RNA predominated in both normal and cirrhotic liver. Variant pMeta-1 mRNA was detected at low levels.
Conclusions: An interaction between HA and CD44 may play a role in the recruitment of numerous infiltrating cells and HA accumulation in hepatic sinusoids. Together with phenotypic changes in the SEC, these results may lead to a disturbance in the elimination of HA during the progression of liver cirrhosis. (C) 2000 Blackwell Science Asia Pty Ltd.