A novel ocular function for decorin in the aqueous humor outflow

Primary open-angle glaucoma, a neurodegenerative disorder characterized by degeneration of optic nerve axons, is a frequent cause of vision loss and blindness worldwide. Several randomized multicenter studies have identified intraocular pressure as the major risk factor for its development, caused by an increased outflow resistance to the aqueous humor within the trabecular meshwork. However, the molecular mechanism for increased outflow resistance in POAG has not been fully established. One of the proposed players is the pro-fibrotic transforming growth factor (TGF)-beta 2, which is found in higher amounts in the aqueous humor of patients with POAG. In this study we elucidated the role of decorin, a small leucine-rich proteoglycan and known antagonist of TGF-beta, in the region of aqueous humor outflow tissue. Utilizing decorin deficient mice, we discovered that decorin modulated TGF-beta signaling in the canonical outflow pathways and the lack of decorin in vivo caused an increase in intraocular pressure. Additionally, the Don(-/-) mice showed significant loss of optic nerve axons and morphological changes in the glial lamina, typical features of glaucoma. Moreover, using human trabecular meshwork cells we discovered that soluble decorin attenuated TGF-beta 2 mediated synthesis and expression of typical downstream target genes including CCN2/CTGF, FN and COL IV. Finally, we found a negative reciprocal regulation of decorin and TGF-beta, with a dramatic downregulation of decorin in the canonical outflow pathways of patients with primary open-angle glaucoma. Collectively, our results indicate that decorin plays an important role in the pathogenesis of primary open-angle glaucoma and offers novel perspectives in the treatment of this serious disease. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

Primary open-angle glaucoma is a neurodegenerative disorder characterized by degeneration of optic nerve axons, with intraocular pressure identified as the major risk factor for its development involving molecular mechanisms like TGF-beta. Decorin has been found to play an important role in intraocular pressure and optic nerve damage.