Secretion of matrix metalloproteinase-3 by co-cultured pigmented and non-pigmented human trabecular meshwork cells following selective laser trabeculoplasty.

ABSTRACT

BACKGROUND: Matrix metalloproteinases (MMPs) are reported to contribute to the mechanism of argon laser trabeculoplasty, but it is unknown whether they are also secreted after selective laser trabeculoplasty (SLT). The aim of this study was to investigate whether human primary trabecular meshwork (HTM) cells secrete MMP-3 after stimulation by SLT. The relationship between SLT and the two principal forms of cell death, apoptosis and necrosis, was also examined. METHODS: Non-pigmented primary HTM cells were challenged with melanin granules to artificially introduce pigmentation. Isolated non-pigmented HTM cells and 11 co-cultures of pigmented and non-pigmented cells were treated with 0.5-1.5 mJ SLT. Cellular metabolic activity (CMA) was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis and necrosis were measured using a cell death ELISA and a lactate dehydrogenase assay, respectively. MMP-3 secretion was measured by ELISA. RESULTS: Co-cultures exhibited a dose-dependent decline in CMA and a dose-dependent increase in necrosis 4 and 24 h after SLT. Non-pigmented cells did not undergo necrosis and displayed a trend towards increased CMA. Apoptosis was reduced in non-pigmented cells but elevated in co-cultures. Increased MMP-3 secretion was observed from co-cultures but not isolated non-pigmented cells. CONCLUSIONS: Pigmentation is necessary for both post-SLT cell death and MMP-3 secretion. SLT appears to have a hormetic effect on non-pigmented HTM cells.