Glaucoma is the leading cause of irreversible blindness worldwide, with its primary risk factor arising from elevated intraocular pressure (IOP) due to an imbalance between aqueous humor production and outflow. This study aims to establish quantitative correlations among IOP, iris mechanical properties, channel microstructures, and aqueous humor dynamics through three-dimensional modeling and finite element analysis, overcoming the limitations of conventional experimental techniques in studying aqueous flow within the trabecular meshwork (TM) outflow pathway. A three-dimensional fluid-structure interaction (FSI) model incorporating the layered TM structure, Schlemm's canal (SC), iris, and other anterior segment tissues was developed based on human ocular anatomy. FSI simulations were performed to quantify the effects of IOP variations and iris Young's modulus on tissue morphology and aqueous humor dynamics parameters. The computational results demonstrated that axial iris deformation showed significant correlations with IOP and iris Young's modulus. Although elevated IOP exhibited minimal effects on hydrodynamic parameters in the anterior and posterior chambers, it markedly suppressed aqueous flow velocity in the TM region. Additionally, wall shear stress in SC and collector channels displayed high sensitivity to IOP variations. These findings reveal that the tissue mechanics-FSI mechanism modulates outflow resistance by regulating aqueous humor dynamics, offering valuable references for developing clinical therapies targeting IOP reduction in glaucoma management.
Humans ; Trabecular Meshwork/anatomy & histology* ; Finite Element Analysis ; Aqueous Humor/metabolism* ; Intraocular Pressure/physiology* ; Glaucoma/physiopathology* ; Iris/anatomy & histology* ; Computer Simulation ; Models, Biological

PURPOSE: To determine the possible effects of chronic exposure of low dose benzalkonium chloride (BAK) on trabecular meshwork cells, and to characterize the pathways involved in the effects. METHODS: Trabecular meshwork cells were treated with 0.0005%, 0.00075%, 0.001%, and 0.0025% BAK for 10 minutes; then, the cells were transferred to a new medium for 24 hours. This process was repeated three times. Cell survival was assessed using the MTT assay to determine the non-apoptotic BAK concentration. Senescence-associated (SA)-β-gal staining was performed to compare quantitatively the cellular senescence of BAK-treated cells with the control group. Cells treated with BAK were analyzed by western blot to determine whether the expressions of cell cycle regulators were affected. RESULTS: Two concentrations (0.0005% and 0.00075%) showed persistent cell viability and were chosen for further experiments. After SA-β-gal staining, cells treated with 0.0005% and 0.00075% BAK showed 28% (± 2.08), 37% (± 2.08) increases in cellular senescence expression, respectively, when compared with control cells (p < 0.05). To identify the molecular pathways involved in cell cycle arrest via BAK, western blot analysis was performed on trabecular meshwork cells, resulting in decreased expressions of cyclin E/CDK2, and increased expressions of the upper stream control molecules, p53 and p21. CONCLUSIONS: Chronic exposure to low dose BAK accelerated cell senescence through cell cycle arrest. Because senescent cells of the trabecular meshwork can inhibit its outflow pathway function and ultimately worsen the glaucomatous process, long-term usage of topical glaucoma medications containing BAK should be conducted with caution.
Aging ; Benzalkonium Compounds ; Blotting, Western ; Cell Aging ; Cell Cycle ; Cell Cycle Checkpoints ; Cell Survival ; Cyclins ; Glaucoma ; Rivers ; Trabecular Meshwork

PURPOSE: Phosphodiesterase (PDE) inhibitors increase matrix metalloproteinase (MMP) production by inhibiting re-uptake of adenosine and may potentiate nitric oxide (NO) activity. This study was performed to investigate the effects and mechanisms of PDE inhibitors on trabecular outflow in cultured human trabecular meshwork cells (HTMCs). METHODS: Primary HTMC cultures were exposed to 0, 20, and 50 µM dipyridamole (DPD) or theophylline (TPN). Permeability through the HTMC monolayer was assessed using carboxyfluorescein. The production of NO was assessed using the Griess assay and MMP-2 levels were measured via Western blotting. RESULTS: DPD significantly increased permeability accompanied with increased nitrite concentration and MMP-2 levels (all p < 0.05). TPN increased nitrite but did not affect permeability or MMP-2 levels significantly (p > 0.05). When treated with DPD and TPN together, both permeability and nitrite production were increased; however, MMP-2 levels showed no difference compared to DPD exposure alone (p > 0.05). CONCLUSIONS: DPD increased trabecular permeability accompanied with increased nitrite production and MMP-2 levels. PDE inhibitors may increase trabecular outflow by increasing MMP-2 levels and by potentiating NO activity through cyclic GMP in HTMC.
Adenosine ; Blotting, Western ; Cyclic GMP ; Dipyridamole ; Humans ; Matrix Metalloproteinases ; Nitric Oxide ; Permeability ; Phosphodiesterase Inhibitors ; Theophylline ; Trabecular Meshwork

A 10-year-old intact female Jindo dog was presented with a 1-week history of conjunctival redness and ocular discharge in the left eye. There was an absence of menace response, dazzle reflex, and direct pupillary light reflex. Slit-lamp biomicroscopy revealed corneal edema, ciliary flush, and aqueous flare. Intraocular pressure was 68 mmHg. Based on the information available, a diagnosis of glaucoma and uveitis was made. Subsequent histopathologic examination showed the glaucoma was produced by the effects of goniodysgenesis, posterior synechia, and pigment dispersion in the trabecular meshwork. This is the first report of primary glaucoma caused by goniodysgenesis in Jindo dogs.
Animals ; Aqueous Humor ; Child ; Corneal Edema ; Diagnosis ; Dogs ; Female ; Glaucoma ; Humans ; Intraocular Pressure ; Reflex ; Trabecular Meshwork ; Uveitis

Glaucoma is a progressive degenerative disease of the optic nerve head, characterized by a specific pattern of axonal loss and visual field deterioration. This review aims at introducing the different novel pharmacologic agents for its treatment, as well as their mechanisms. Most glaucoma patients require lifelong care and individualized treatment. Intraocular pressure (IOP), which is regulated by aqueous humor production, outflow via the trabecular meshwork (parasympathomimetics only) and uveoscleral outflow pathways, is currently the only treatable target for glaucoma treatment. Conventional glaucoma medications are categorized as β blockers, α agonists, carbonic anhydrase inhibitors, parasympathomimetics, and prostaglandin analogues. The development of basic research-derived novel classes of pharmacologic agents features novel action mechanisms, which are different from those of conventional medications. New classes of recently approved or clinical trial-tested medications include Rho-kinase inhibitors, nitric oxide donors, adenosine agonists, and prostaglandin analogs targeting E-type prostanoid receptors, etc. Their integration and future development will facilitate the expansion and customization of therapeutic options.
Adenosine ; Aqueous Humor ; Axons ; Carbonic Anhydrase Inhibitors ; Glaucoma ; Humans ; Intraocular Pressure ; Nitric Oxide Donors ; Ocular Hypertension ; Optic Disk ; Parasympathomimetics ; Prostaglandins, Synthetic ; rho-Associated Kinases ; Trabecular Meshwork ; Visual Fields

PURPOSE: We investigated the extent of adenosine A1 agonist-induced expression and regulation of matrix metalloproteinase 2 (MMP-2) synthesis in human trabecular meshwork cells (HTMC). METHODS: Primary HTMC cultures were exposed to 0.1 or 1.0 µM N6-cyclohexyladenosine (CHA) for 2 h in the presence or absence of an inhibitor thereof, 8-cyclopentyl-1,3-dimethylxanthine (CPT). The expression level of mRNA encoding MMP-2 was assessed via reverse transcription-polymerase chain reaction, and the levels of tissue inhibitor of metalloproteinase 2 (TIMP2) and membrane-type-1 MMP (MT1-MMP) measured by Western blotting. The permeability of the HTMC monolayer was assessed with the aid of carboxyfluorescein. RESULTS: CHA at 1.0 µM increased the permeability of the HTMC monolayer (p = 0.003) and CHA at both 0.1 and 1.0 µM significantly increased MMP-2 mRNA expression, which was inhibited by co-exposure to CPT (all p < 0.05). CHA increased MMP-2 activity, decreased that of TIMP2, and increased that of MT1-MMP (all p < 0.05). CONCLUSIONS: CHA increased the permeability of the HTMC monolayer and increased MMP-2 activity, decreased TIMP2 activity, and increased MT1-MMP activity. Thus, regulation of TIMP2 and MT1-MMP expression may be involved in the adenosine A1 agonist-induced increase in MMP-2 activity.
Adenosine ; Blotting, Western ; Humans ; Matrix Metalloproteinase 14 ; Matrix Metalloproteinase 2 ; Permeability ; RNA, Messenger ; Tissue Inhibitor of Metalloproteinase-2 ; Trabecular Meshwork

PURPOSE: To investigate the effects of high glucose (HG) and dexamethasone (DEX) on the survival and permeability of trabecular meshwork cells (HTMC), and associated changes in tight junctions. METHODS: Primary cultured HTMC were exposed to 5 mM low glucose (LG) or 25 mM HG with or without 1.0 µM DEX for 3 days. The permeability of the HTMC monolayer was assessed using carboxyfluorescein or transendothelial electrical resistance (TEER). Gene and protein expressions of claudin-5 and occludin were assessed with reverse transcription polymerase chain reaction (RT-PCR) and Western blot, respectively. RESULTS: HG was significantly associated with greater HTMC monolayer permeability compared to LG by both the carboxyfluorescein permeability test and TEER (p = 0.022, 0.028). HG also decreased claudin-5 and occludin mRNA expression, respectively (7.5%, 12.9%). DEX abolished HG-induced increased permeability, and increased the protein expression of claudin-5 and occludin, respectively (p = 0.015, 0.012). CONCLUSIONS: In HTMCs, DEX reversed HG-induced permeability increase. DEX increased tight junction molecules claudin-5 and occludin. Thus, DEX-induced changes in junctional proteins could be another mechanism of increased resistance through the trabecular meshwork and may result in steroid-induced glaucoma.
Blotting, Western ; Claudin-5 ; Dexamethasone ; Electric Impedance ; Glaucoma ; Glucose ; Occludin ; Permeability ; Polymerase Chain Reaction ; Reverse Transcription ; RNA, Messenger ; Tight Junctions ; Trabecular Meshwork

PURPOSE: To investigate the effects of valproic acid on the production of nitric oxide (NO) and expression of endothelial nitric oxide synthase (eNOS) in cultured human trabecular meshwork cells (HTMC). METHODS: Primarily cultured HTMC were exposed to 0.25, 0.5, and 1.0 mM valproic acid for 6, 12, and 24 hours. Expression of eNOS mRNA was assessed with Reverse transcription-polymerase chain reaction, and production of NO was assessed with Griess assay. Cellular survival was assessed with the 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. RESULTS: Valproic acid at concentrations of 0.25, 0.5, 1.0 mM did not affect the cellular survival of HTMC significantly after exposure for 24 hours. Valproic acid increased NO production in a dose- and time-dependent manner. Also, valproic acid increased the degree of eNOS mRNA expression in a dose-dependent manner in HTMC. CONCLUSIONS: Valproic acid increases production of NO and expression of eNOS mRNA in HTMC. Thus, valproic acid might increase aqueous outflow through the trabecular meshwork.
Humans ; Nitric Oxide Synthase Type III ; Nitric Oxide Synthase ; Nitric Oxide ; RNA, Messenger ; Trabecular Meshwork ; Valproic Acid

PURPOSE: To investigate the effects of tetrahydrozoline (THZ) on the survival of cultured human trabecular meshwork cells (HTMC) and the permeability of HTMC monolayer. METHODS: Primary cultured HTMC were exposed to an adrenergic agonist (0.01, 0.1, 1.0 or 10 µM THZ) for 1 day and 3 days. Carboxyfluorescein permeability through the HTMC monolayer was measured using Transwell. Cellular viability and nitric oxide (NO) production were assessed using MTT and Griess assays, respectively. RESULTS: THZ did not affect the cellular survival (p > 0.05) or NO production (p > 0.05). THZ significantly increased the carboxyfluorescein permeability through the HTMC monolayer in a dose-dependent manner compared with non-exposed control (p < 0.05) after exposure for 1 and 3 days. CONCLUSIONS: THZ does not affect the survival of HTMC but decreases the permeability of HTMC monolayer in a dose-dependent manner. Thus, THZ may possibly decrease trabecular outflow.
Adrenergic Agonists ; Humans ; Nitric Oxide ; Permeability* ; Trabecular Meshwork*

PURPOSE: To evaluate the effects of trypan blue (TB) on the survival of cultured human trabecular meshwork cells (HTMCs). METHODS: Primarily cultured HTMCs were exposed to 0.05, 0.10 or 0.50% TB for 1, 5 or 30 min. Cellular survival was assessed using the MTT assay and degree of apoptosis was analyzed with flow cytometry using annexin-V/propidium iodide double staining. RESULTS: Long-term exposure or high concentration of TB decreased the survival of HTMCs (p < 0.05). In flow cytometric analysis, exposure to 0.50% TB for 30 min increased the degree of apoptosis (p < 0.05). Commercial TB decreased cell survival after exposure for 5 min and increased the degree of apoptosis after exposure for 30 min (p < 0.05). CONCLUSIONS: TB may cause cellular damage of cultured HTMCs and apoptosis could be the underlying mechanism. In TB-assisted cataract surgery, TB should be used for the shortest time possible and removed completely.
Apoptosis ; Cataract ; Cell Survival ; Flow Cytometry ; Humans ; Trabecular Meshwork* ; Trypan Blue*