Stimulatory effects of ascorbic acid on hyaluronic acid synthesis of in vitro cultured normal and glaucomatous trabecular meshwork cells of the human eye.

The outflow of aqueous humor of the primate eye occurs across the filter system of the trabecular meshwork (TM) into Schlemm's canal. Cells of TM derived from a normal (TM-N-cells) and a glaucomatous human eye (TM-G-cells) were established in monolayer culture. The present comparative experiments were performed with cells kept in a defined serum-free medium (the aqueous humor is nearly protein-free!). Under these conditions the cells stay alive for several months in a non-proliferating state. TM-G-cells exhibited a lower synthesis rate of glycosaminoglycans-especially of hyaluronic acid (HA)--than TM-N-cells. Addition of 50-200 micrograms/ml ascorbic acid (the aqueous humor is characterized by a high ascorbic acid concentration of about 150 micrograms/ml) to the culture medium resulted in a significant dose-dependent stimulation of HA-synthesis and secretion, which was relatively stronger in case of TM-G-cells than with TM-N-cells. Thus, the results suggest a role of ascorbic acid in the probably membrane-localized HA-synthesis. Functions of ascorbic acid and HA for the morphological and functional integrity of the TM-cells in vitro and the outflow apparatus in vivo were discussed.