EARLY CHANGES IN MATRIX METALLOPROTEINASES AND INHIBITORS AFTER IN-VITRO LASER TREATMENT TO THE TRABECULAR MESHWORK

Extracellular matrix turnover in the trabecular meshwork may play a ro le in regulating aqueous humor outflow. Laser trabeculoplasty is a com mon treatment for open-angle glaucoma. The mechanism of this treatment is not understood. We investigated changes in the levels and expressi on of the matrix metalloproteinases and their tissue inhibitors (TIMPs ) in this tissue using cultured human anterior segment explants and st andard clinical-parameter laser treatment. Medium gelatinase A activit y levels are relatively high for sham-treated controls and are not cha nged dramatically following laser treatment. Medium gelatinase B and s tromelysin activity levels are low in sham-treated explants and increa se significantly by 24 h after treatment. TIMP1 levels, as assessed by immunoblots of Western transfers, are initially low. However, by 24 h TIMP1 levels have increased significantly. Using semi-quantitative re verse transcription and the polymerase chain reaction, mRNA levels of stromelysin, gelatinase B and TIMP1 are shown to increase after laser treatment, while gelatinase A and TIMP2 remain relatively constant. Th e increases in trabecular stromelysin and gelatinase B in response to laser trabeculoplasty may have important implications for the mechanis m of action of this treatment for open-angle glaucoma.