Glaucoma is a progressive optic neuropathy frequently associated with elevated intraocular pressure (IOP) and extracellular matrix (ECM) remodeling at the optic nerve head and trabecular meshwork (TM). Oxidative stress and transforming growth factor-β (TGF-β) signaling pathway disruptions are among the important recognized risk factors of glaucoma pathogenesis. Patients with glaucoma have elevated levels of TGF-β2 in their aqueous humor. The bone morphogenetic proteins (BMP) are other members of the TGF-β superfamily that modify TGF-β signaling in several tissues including TM. Additionally, gremlin, an antagonist of BMP, has been showed to be elevated in aqueous humor of glaucoma patients. Mutations in LTBP2 that encodes the ECM protein latent TGF-β binding protein 2 cause of primary congenital glaucoma and other disorders that often manifest secondary glaucoma. It has been suggested that LTBP2 role in disease processes via its effects on TGF-β activation. Oxidative stress is an important mechanism relevant to a large spectrum of neurodegenerative disorders including glaucoma. Many studies have confirmed oxidative stress biomarkers in glaucomatous tissues. In this study we investigated the role of TGF-β signaling pathway activation, LTBP2 gene knock down and oxidative stress in the expression of ECM genes in TM cells.

Primary cultured human TM cells were treated with TGFβ2, gremlin, LTBP2 siRNA, H2O2 and N-Acetyl-L-cysteine (NAC) + H2O2. H2O2 induces oxidative stress and NAC is an antioxidant and serves as negative control for oxidative stress events. Real time PCR analysis was used to determine the expression of 12 ECM related genes including matrix metalloproteinase (MMPs) genes.

TGFβ2, gremlin, LTBP2 siRNA and H2O2 increased expression of some of ECM structural genes and decreased some MMP genes in TM cells. The patterns of effects were specific for each treatment, although there was some overlap.

Oxidative stress and TGF-β signaling which are important entities in the etiology of glaucoma exert their effects at least partially by causing increased production of ECM proteins in the TM. The TM is an essential component of aqueous fluid outflow and disturbances in its functions cause increased IOP, thus affecting glaucoma.