DEXAMETHASONE TREATMENT DECREASES HYALURONAN-FORMATION BY PRIMATE TRABECULAR MESHWORK CELLS IN-VITRO

The functional significance of Hyaluronan (HA) present in the cribrifo rm layer of Schlemm's canal is not known. It may contribute to the act ual outflow resistance but the relatively inert molecule might also be necessary to prevent adherence of larger molecules to the cribriform network. Thus HA might rather prevent an increase in outflow resistanc e. It is well known that treatment with Dexamethasone (DM) in a number of patients leads to an increase in intraocular pressure presumably d ue to an increase in outflow resistance. To clarify whether an imbalan ce in HA formation might be involved in these changes we have treated confluent cultures of human trabecular cells as well as control cell l ines (ciliary muscle cells, scleral fibroblasts) with 500 nM DM for 24 hr or 12 days and have measured HA-synthesis using incorporation assa ys with 0.05 m D-[6-H-3] Glucosamine hydrochloride. In all six cell li nes investigated there was a significant decrease in HA-synthesis foll owing short and long term treatment with DM when compared with the unt reated centrals. This reaction of trabecular cells to DM treatment is different from the DM effect reported on the synthesis of many other c omponents of the extracellular matrix like fibronectin and elastin whi ch increase after DM treatment. If the DM-effect seen in cell cultures plays a role in vivo decreased formation in KA could result in impair ed function of the outflow pathways. (C) 1997 Academic Press Limited.