Thrombospondin-2 is up-regulated by TGFβ2 and increases fibronectin expression in human trabecular meshwork cells.

Elevated intraocular pressure (IOP) is a major risk factor for the development of primary open-angle glaucoma (POAG). This is from an increased aqueous humour (AH) outflow resistance through the trabecular meshwork (TM). The pathogenic mechanisms leading to the increase in TM outflow resistance are poorly understood but are thought to be from a dysregulation of the TM extracellular matrix (ECM) environment. ECM modification and turnover are crucial in regulating the resistance to aqueous outflow. ECM turnover is influenced by a complex interplay of growth factors such as transforming growth factors (TGFβ) family and matrix metalloproteinases (MMPs). Elevated TGFβ2 levels result in an increase in ECM deposition such as fibronectin leading to increased resistance. Fibronectin is a major component of TM ECM and plays a key role in its maintenance. Thrombospondins (TSP)-1 and -2 are important regulators of the ECM environment. TSP-1 has been implicated in the pathogenesis of POAG through activation of TGFβ2 within the TM. TSP-2 does not contain the catalytic domain to activate latent TGFβ, but is able to mediate the activities of MMP 2 and 9, thereby influencing ECM turnover. TSP-2 knock out mice show lower IOP levels compared to their wild type counterparts, suggesting the involvement of TSP-2 in the pathogenesis of POAG but its role in the pathogenesis of POAG remains unclear. The purpose of this study was to investigate the role of TSP-2 in trabecular meshwork ECM regulation and hence the pathogenesis of POAG. TSP-1 and TSP-2 expressions in immortalised glaucomatous TM cells (GTM3) and primary human non-glaucomatous (NTM) and glaucomatous cells (GTM) were determined by immunocytochemistry, immuno-blot analysis and qPCR following treatment with TGFβ2 and Dexamethasone. The level of ECM protein fibronectin was determined in TM cells using immuno-blot analysis following treatment with TSP-1 or -2. TM cells secrete TSP-1 and -2 under basal conditions at the protein level and TSP-2 mRNA and protein levels were increased in response to TGFβ2 three days post treatment. Exogenous treatment with TSP-2 up-regulated the expression of fibronectin protein in GTM3 cells, primary NTM and GTM cells. TSP-1 did not affect fibronectin protein levels in GTM3 cells. This suggests that the role of TSP-2 might be distinct from that of TSP-1 in the regulation of the TM cell ECM environment. TSP-2 may be involved in the pathogenesis of POAG and contribute to increased IOP levels by increasing the deposition of fibronectin within the ECM in response to TGFβ2.

Kennedy SM ，Sheridan C ，Kearns VR ，Bilir EK ，Fan X ，Grierson I ，Choudhary A ... -  《-》

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

Fleenor DL ，Shepard AR ，Hellberg PE ，Jacobson N ，Pang IH ，Clark AF ... -  《INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE》

Identification of Missense Extracellular Matrix Gene Variants in a Large Glaucoma Pedigree and Investigation of the N700S Thrombospondin-1 Variant in Normal and Glaucomatous Trabecular Meshwork Cells.

Wirtz MK ，Sykes R ，Samples J ，Edmunds B ，Choi D ，Keene DR ，Tufa SF ，Sun YY ，Keller KE ... -  《-》

Astragaloside IV Attenuates Ocular Hypertension in a Mouse Model of TGFβ2 Induced Primary Open Angle Glaucoma.

Kasetti RB ，Maddineni P ，Kodati B ，Nagarajan B ，Yacoub S ... -  《-》

Effects of TGF-beta2, BMP-4, and gremlin in the trabecular meshwork: implications for glaucoma.

Wordinger RJ ，Fleenor DL ，Hellberg PE ，Pang IH ，Tovar TO ，Zode GS ，Fuller JA ，Clark AF ... -  《INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE》