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Background: Mutations in myocilin, a 55-57 kDa secreted glycoprotein, are causative for some forms of primary open-angle glaucoma (POAG). In vitro studies indicate that myocilin can modulate the hydrodynamic outflow resistance in the trabecular meshwork (TM) and that elevated amounts of myocilin can obstruct the TM outflow system in POAG. In this study, we analyzed the localization of myocilin in the trabecular meshwork (TM) of eyes with primary open-angle glaucoma (POAG), and compared it with that of normal eyes., Methods: Immunohistochemistry for myocilin was performed in the eyes of human donors (nine normal and 14 with POAG, including one with steroid-induced glaucoma)., Results: Staining for myocilin was observed in the extracellular spaces of the juxtacanalicular tissue (JCT) in all normal eyes. Some normal eyes did also show cytoplasmic staining for myocilin in TM cells. In the eyes of six donors with POAG, staining of the JCT was more widespread and intense than in normal eyes. In the other eyes with POAG, immunoreactivity for myocilin in the JCT was not markedly different to that of normal eyes. Staining intensity in the JCT of POAG eyes did not obviously correlate with intraocular pressure or clinical severity. In the eyes of one patient with steroid-induced POAG, cells of the TM, Schlemm's canal endothelium, and the anterior stroma of the iris showed an immunoreactivity for myocilin which was considerably more intense than in normal eyes, or in the eyes with other forms of POAG., Conclusions: In some cases of POAG, the structural changes in the JCT include an increase in myocilin in the extracellular pathways of aqueous humor. Treatment with steroids appears to increase myocilin synthesis in TM and iris of human eyes in situ.

Transforming growth factor-beta2 (TGF-beta2) is elevated in the aqueous humor of patients with primary open-angle glaucoma (POAG), and high levels of TGF-beta2 are thought to contribute to the pathogenesis of POAG. Most TGF-beta2 in the eye is present in a latent, inactive form and the mechanisms of its in vivo activation are unclear. Since thrombospondin-1 (TSP-1) is one of the most potent in vivo activating molecules of TGF-betas, we investigated the localization and expression of TSP-1 in the aqueous humor outflow pathways. TSP-1 immunohistochemistry was performed in the eyes of human donors (8 normal and 17 with glaucoma). In addition, the eyes of Tsp-1(-/-)-deficient mice and normal Tsp-1(+/+) mice were investigated. TSP-1 mRNA expression was assessed by reverse transcription-polymerase chain reaction and Northern blotting of RNA from fresh trabecular meshwork (TM), and human and mouse TM cells in vitro. In addition, Northern and Western blot analyses of TM cells after incubation with TGF-beta and dexamethasone were performed. In most of the eyes, TSP-1 immunolabeling was predominantly observed in extracellular areas of the juxtacanalicular (cribriform) part of the TM. Some focal staining was observed in the corneoscleral and uveal parts of the TM. In the eyes of six glaucoma patients (including one with steroid-induced glaucoma), TSP-1 immunoreactivity was considerably more intense and all regions of the TM were positively labeled. In double labeling experiments, staining for TSP-1 did not overlap with that of fibronectin or type VI collagen. mRNA for TSP-1 was detected in both fresh and cultured TM cells. Incubation of TM cells with TGF-beta1 and dexamethasone caused a marked increase in TSP-1 expression. TSP-1 in the TM might act as a potent local endogenous activator of TGF-betas in the aqueous humor and mediate any local effects of TGF-beta and/or dexamethasone on the outflow of aqueous humor.

Mutations in myocilin, a 55–57 kDa secreted glycoprotein, are causative for some forms of primary open-angle glaucoma (POAG). In vitro studies indicate that myocilin can modulate the hydrodynamic outflow resistance in the trabecular meshwork (TM) and that elevated amounts of myocilin can obstruct the TM outflow system in POAG. In this study, we analyzed the localization of myocilin in the trabecular meshwork (TM) of eyes with primary open-angle glaucoma (POAG), and compared it with that of normal eyes. Immunohistochemistry for myocilin was performed in the eyes of human donors (nine normal and 14 with POAG, including one with steroid-induced glaucoma). Staining for myocilin was observed in the extracellular spaces of the juxtacanalicular tissue (JCT) in all normal eyes. Some normal eyes did also show cytoplasmic staining for myocilin in TM cells. In the eyes of six donors with POAG, staining of the JCT was more widespread and intense than in normal eyes. In the other eyes with POAG, immunoreactivity for myocilin in the JCT was not markedly different to that of normal eyes. Staining intensity in the JCT of POAG eyes did not obviously correlate with intraocular pressure or clinical severity. In the eyes of one patient with steroid-induced POAG, cells of the TM, Schlemm’s canal endothelium, and the anterior stroma of the iris showed an immunoreactivity for myocilin which was considerably more intense than in normal eyes, or in the eyes with other forms of POAG. In some cases of POAG, the structural changes in the JCT include an increase in myocilin in the extracellular pathways of aqueous humor. Treatment with steroids appears to increase myocilin synthesis in TM and iris of human eyes in situ. [ABSTRACT FROM AUTHOR]

The development of the chamber angle was studied in the eyes of heterozygous Pax6lacZ/+ mutant mice (Nature 387 (1997) 406). Mutations in PAX6 cause aniridia, a condition that is frequently associated with glaucoma, a blinding disease that may be associated with chamber angle defects. Mesenchymal cells were seen in the chamber angle at P1–P5. In wild-type mice, these cells differentiated into typical trabecular meshwork (TM) cells next to Schlemm''s canal. In Pax6lacZ/+ mice, TM cells remained undifferentiated and Schlemm''s canal was absent. From P1 to P4, staining for β-galactosidase and immunoreactivity for Pax6 were observed in chamber angle mesenchyme, but were absent later. Cultured murine TM cells expressed Pax6. The defects in chamber angle and TM differentiation were associated with a wide spectrum of other anterior eye defects, which included various degrees of iris hypoplasia and corneal haze, isolated iridocorneal adhesions and atypical coloboma, and a vascularized cornea in all adult animals. A third of the animals showed Peters'' anomaly including corneal opacity and iridocorneal adhesions. The separation of the lens from the cornea was incomplete, and epithelial layers of lens and cornea were continuous. Pax6 activity is directly required for differentiation of the chamber angle. Variations in phenotype of Pax6lacZ/+ mice appear not to involve direct dominant-negative or dose-dependent effects. [Copyright &y& Elsevier]

In glaucoma therapy, nanoparticles (NPs) are a favorable tool for delivering drugs to the outflow tissues of the anterior chamber of the eye where disease development and progression take place. In this context, a prerequisite is an efficient enrichment of NPs in the trabecular meshwork with minimal accumulation in off-target tissues such as the cornea, lens, iris and ciliary body. We evaluated the optimal size for targeting the trabecular meshwork by using gold NPs of 5, 60, 80 and 120 nm with a bare surface (AuNPs) or coated with hyaluronic acid (HA-AuNPs). NPs were compared regarding their colloidal stability, distribution in the anterior chamber of the eye ex vivo and cellular uptake in vitro. HA-AuNPs demonstrated an exceptional colloidal stability. Even after application into porcine eyes ex vivo, the HA coating prevented an aggregation of NPs inside the trabecular meshwork. NPs with a diameter of 120 nm exhibited the highest volume-based accumulation in the trabecular meshwork. Off-target tissues in the anterior chamber demonstrated an exceptionally low gold content. Our findings are particularly important for NPs with encapsulated anti-glaucoma drugs because a higher particle volume would be accompanied by a higher drug payload. [ABSTRACT FROM AUTHOR]

• Decorin deficiency leads to elevated intraocular pressure in mice. • TGF-β target genes are enriched in the conventional outflow pathways of decorin-deficient mice. • Decorin attenuates the expression of TGF-β2 in cultured HTM cells. • Decorin levels are reduced in the chamber angle of glaucomatous eyes. 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)-β2, 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-β, in the region of aqueous humor outflow tissue. Utilizing decorin deficient mice, we discovered that decorin modulated TGF-β signaling in the canonical outflow pathways and the lack of decorin in vivo caused an increase in intraocular pressure. Additionally, the Dcn −/− 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-β2 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-β, 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. [ABSTRACT FROM AUTHOR]