How does the hyaluronan scrap-yard operate?

Hyaluronan is an extracellular polysaccharide found throughout the extracel lular matrix, especially in soft connective tissue. It has an unusual featu re, in that its turnover rate is much greater than that of other extracellu lar matrix components. The mechanisms of its synthesis at the plasma membra ne (by hyaluronan synthases) and lysosomal degradation (by hyaluronidases) are well documented. However, the mechanisms by which it enters those cells primarily involved in its degradation remain a mystery. Recent work now su ggests that a novel scavenger receptor expressed on the surface of liver en dothelial cells is responsible for part of this degradative process. Furthe r study is required to fill the remaining gaps in our knowledge about this process in other tissues. (C) 1999 Elsevier Science B.V./International Soci ety of Matrix Biology. All rights reserved.