TGFbeta2-induced changes in human trabecular meshwork: implications for intraocular pressure

PURPOSE: Transforming growth factor (TGF)-beta2 levels are elevated in glaucomatous human aqueous humor. TGFbeta is a cytokine that alters extracellular matrix (ECM) metabolism, and excess ECM has been proposed to increase aqueous outflow resistance in the trabecular meshwork (TM) of glaucomatous eyes. This study was undertaken to investigate effects of TGFbeta2 on secretion of fibronectin and the protease inhibitor plasminogen activator inhibitor (PAI)-1 from human TM cell cultures and perfused human ocular anterior segments. METHODS: Total RNA was isolated from pooled human TM cell monolayers and used for a gene microarray expression analysis. Supernatants from treated human TM cells were analyzed by ELISA for fibronectin or PAI-1 content. TGFbeta2 effects on intraocular pressure (IOP) were evaluated in a perfused organ culture model using human anterior segments, and eluates were analyzed for fibronectin and PAI-1 content. RESULTS: Overnight treatment of TM cells with TGFbeta2 upregulated multiple ECM-related genes, such as PAI-1. TGFbeta2 also increased secretion of both fibronectin and PAI-1 from TM cells. TGFbeta2 effects on TM cells were blocked by inhibitors of the TGFbeta type I receptor. In perfused human anterior segments, TGFbeta2 treatment elevated IOP and increased eluate fibronectin and PAI-1 content. CONCLUSIONS: TGFbeta2 effects on IOP may be transduced by TGFbeta type-I receptor-mediated changes in TM secretion of ECM-related factors such as fibronectin and PAI-1. Modulation of TGFbeta2-induced changes in the ECM may provide a novel and viable approach to the management of glaucoma.