Histological investigation of human glaucomatous eyes: Extracellular fibrotic changes and galectin 3 expression in the trabecular meshwork and optic nerve head

Abstract

Glaucoma is a leading cause of irreversible 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 in extracellular matrix components (ECM) including collagen, elastin, transforming growth factor beta-2, type-II receptor (TGFβRII) and Galectin3 (Gal3) in the glaucomatous human eyes to quantify fibrotic changes in ONH and TM. Glaucomatous and control human donor eyes were prepared for chemical and immunological staining to quantify ECM protein expression in the TM and ONH. Chemical staining included: Trichrome (collagen), Vernhoeff-Van Giesen (elastin) and Sirius Red (collagen). Immunohistochemistry was used to determine levels of Gal3 and TGFβ2RII. Quantitative analyses were performed using Image J software. Student's t-test was used to compare groups and Pearson's test was used to determine correlations P-values of 0.05 (or less) were considered statistically significant. Deposition of ECM proteins was elevated in glaucomatous tissues. There was increased collagen (P = 0.0469), Gal3 (P < 0.0001) and TGFβ2RII (P = 0.0005) in the TM of glaucomatous eyes. Likewise, collagen (P = 0.0517) and Galectin3 (P = 0.041) were increased in the ONH glaucomatous eyes. There was a correlation of TGFβRII with Gal3 in the TM (P < 0.0001) and optic nerve (P = 0.0003). The TM and ONH of glaucomatous eyes showed increased expression of ECM proteins supporting a fibrotic pathology. Galectin3 and TGFβ-2R II showed a positive correlation in TM and optic nerve supporting co-localization and suggesting their potential role in the glaucoma fibrotic process. Clin. Anat. 31:1031-1049, 2018. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Transforming Growth Factor-β Signaling in Fibrotic Diseases and Cancer-Associated Fibroblasts

“…However, under chronic and persistent pathologic circumstances, an uncontrolled fibrotic process results in excessive accumulation of ECM, including collagen, fibronectin, hyaluronic acid, and proteoglycans that leads to fibrosis and ultimately organ failure in fibrotic diseases [25][26][27]. These fibrotic diseases may occur in multi-system diseases, such as systemic sclerosis (SSc) [28], nephrogenic systemic fibrosis (NSF) [29], and specific organs like idiopathic pulmonary fibrosis (IPF), renal fibrosis, hepatic cirrhosis, cardiac fibrosis, oral submucous fibrosis, and glaucoma [30,31].…”

TET-dependent GDF7 hypomethylation impairs aqueous humor outflow and serves as a potential therapeutic target in glaucoma

“…Fibrotic TM was nominated as the predominant pathological event in AH outflow resistance. 20,21 Increased accumulation of collagen was observed in the GTM samples and cells with Masson staining (first lane of Figures S1A and S1B). Also, pro-fibrotic markers, 22 including a-SMA, FN, and Col I, were significantly upregulated in GTM samples and cultured GTM cells.…”

Galectins and their involvement in ocular disease and development

“…TGF-β2 has been demonstrated to be an important factor involved in TM fibrosis (Kang et al, 2013), as evidenced by elevated concentrations of this cytokine in the aqueous humour of patients with primary open angle glaucoma (Tripathi et al, 1994). Concurrently, there is evidence of Gal-3 upregulation in the TM and the ONH of human glaucomatous eyes (Belmares et al, 2018;Fautsch et al, 2003), and given the known significance of Gal-3 involvement in fibrogenic states of other organs (Suthahar et al, 2018), it would be invaluable to elucidate the interaction between Gal-3 and TGF-β in the context of glaucoma.…”

“…Promotes re-epithelialisation (Cao et al, 2002a) Glaucoma Gal-3 Upregulated in the TM and ONH (Belmares et al, 2018;Fautsch et al, 2003) Present in higher concentrations in the aqueous humour (Tripathi et al, 1994) Promotes RGC loss (Abreu et al, 2017) Gal-3 Anchors cells within the TM (Diskin et al, 2009) Ocular immunology…”