Histological Investigation of Human Glaucomatous Eyes: Extracellular Fibrotic Changes and Galectin3 Expression in the Trabecular Meshwork and Optic Nerve Head




Belmares, Ricardo


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Glaucoma is a leading cause of vision loss and is associated with fibrotic changes in two ocular tissues: the optic nerve head (ONH) and trabecular meshwork (TM). We investigated the differences of extracellular components of the two ocular tissues in human glaucomatous eyes to determine fibrotic changes. The extracellular components studied included: collagen, elastin, Galectin 3 (Gal3), and Transforming Growth Factor beta-2 Type II receptor (TGFβ-2 RII). We hypothesized that these components will be increased in glaucomatous eyes using chemical staining and immunohistochemistry. Chemical staining included: Masson's Trichrome and Sirius Red stains (collagen) and Vernhoeff-Van Giesen (elastin). Immunohistochemistry was used to determine expression of Gal3 and TGFβ-2 RII. Data was analyzed using Image J software to quantify expression of the extracellular components. The results from Image J analysis of extracellular components demonstrated an overall increase in glaucomatous tissue. TM studies showed an increase of collagen (P=0.0469), and Gal3 (P [less than] 0.0001), and TGFβ-2 RII (P=0.0005) in glaucomatous eyes. Collagen was apparently increased in ONH ((P=0.0517) and Galectin3 (P=0.041) was increased in myelin transition zone of the glaucomatous optic nerve. Vernhoeff-Van Giesen stain showed increased thickness and irregular arrangement of elastic fibers in ONH. Vernoeff-van Giesen and Sirius Red stains also showed increased staining in glaucomatous tissue, but were not quantifiable with Image J software. Analysis showed a correlation of TGFβ-2 RII with Gal3 in TM (P [less than ]0.0001) and myelin transition zone of optic nerve (P=0.0003). Analysis of extracellular components of TM and ONH showed that glaucomatous eyes demonstrate a fibrotic state. Increased collagen deposition and thickened elastic fibers are recognized features of fibrosis and both TM and ONH revealed these features through chemical staining. Galectin3, another known marker for fibrosis, was also elevated in TM and optic nerve. Moreover, Gal3 co-localization with TGFβ-2 RII suggests that it may be involved with the pro-fibrotic TGFβ-2 signaling pathway.