CORNEAL ENDOTHELIAL HYALURONIDASE - A ROLE IN ANTERIOR-CHAMBER HYALURONIC-ACID CATABOLISM

The possible role of the human corneal endothelium in the turnover of anterior chamber hyaluronic acid (HA) was investigated. Hyaluronidase, an endoglycosidase that degrades HA and other glycosaminoglycans, is thought to play a role in HA homeostasis. The presence of hyaluronidas e in the corneal endothelium was demonstrated immunohistochemically in sections from normal adult human cornea. Additionally, by using a mod ified enzyme-linked immunosorbent assay-like assay, active hyaluronida se was detected in the supernatant from primary culture human corneal endothelial cells. The optimal activity for the corneal endothelial hy aluronidase was in the acid range (pH 4.0), similar to previously isol ated lysosomal hyaluronidase. Further immunohistochemistry showed that the corneal endothelial cells also express CD44, the receptor for HA, which would allow endocytosis of HA. Human corneal endothelial hyalur onidase may play a role in normal anterior segment HA metabolism and i n the degradation of highly concentrated HA used as a viscoelastic.