SEARCH · Search PubMed

Results for “Trabecular Meshwork”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources

PubMed2003

Proteasome inhibition by chronic oxidative stress in human trabecular meshwork cells.

The pathophysiologic mechanisms leading to the malfunction of the trabecular meshwork (TM)-Schlemm's canal (SC) outflow pathway in glaucoma are still unclear. We hypothesize that chronic oxidative stress may contribute to the malfunction of the outflow pathway by impairing the intracellular proteasome system of the cells, decreasing the ability of the tissue to modulate outflow resistance. To study the effects of chronic oxidative stress on proteasome function, primary cultures of human TM cells were incubated under 40% oxygen and proteasome activity was analyzed by measuring the accumulation of enhanced green fluorescent protein fused to a PEST motif. Changes in proteasome content, cellular senescence, and cell viability were also monitored. After 10 days of exposure to chronic oxidative stress, TM cells showed a marked decline in proteasome activity that was associated with premature senescence and decreased cell viability. These results suggest that proteasome failure may be involved in glaucoma pathophysiology.

Cell Survival↗

PubMed2004

Effects of donor age on proteasome activity and senescence in trabecular meshwork cells.

The mechanisms involved in the progressive malfunction of the trabecular meshwork (TM) in glaucoma are not yet understood. To study age-related changes in human TM cells, we isolated primary TM cell cultures from young (ages 9, 14, and 25) and old (ages 66, 70, and 73) donors, and compared levels of oxidized proteins, autofluorescence, proteasome function, and markers for cellular senescence. TM cells from old donors showed a 3-fold increase in oxidized proteins and a 7.5-fold decrease of proteasome activity. Loss of proteasome function was not associated with decreased proteasome content but with partial replacement of the proteolytic subunit PSMB5 with the inducible subunit LMP7. Cells from old donors also demonstrated features characteristic of cellular senescence associated with phosphorylation of p38MAPK but only a modest increase in p53. These data suggest that age-related proteasome inhibition and cellular senescence could contribute to the pathophysiological alterations of the TM in glaucoma.

Adolescent↗

PubMed1999

The effects of protein kinase C on trabecular meshwork and ciliary muscle contractility.

PURPOSE: The possible role of protein kinase C (PKC) inhibitors in novel pressure-lowering drugs is currently under investigation. To gain further insight into regulation of contractility by PKC in trabecular meshwork (TM) and ciliary muscle (CM), the effects of various PKC inhibitors and activators were tested. METHODS: Isometric tension measurements of bovine TM and CM strips were performed. PKC was stimulated by phorbol ester and by the diacylglycerol analogue diC8. PKC blockade was accomplished using H7 and myristoilated PKC substrate (mPKC). Western blot analysis was used to identify specific PKC isoforms in human trabecular meshwork (HTM), human ciliary muscle (HCM), and bovine TM and CM. RESULTS: In tissues precontracted by carbachol PKC antagonist H7 led to a relaxation of TM (25+/-7.2 versus 100%; n = 8) with no effect on CM. mPKC substrate selectively blocks PKC. This substance led to relaxation of TM (32.8+/-7.4 versus 100%, n = 7), whereas CM was not affected. PMA at concentrations of 10(-6) M led to a slow contraction of both tissues that was more marked in TM. DiC8 and 4alpha-phorbol had no effect on contractility. Western blot analysis revealed expression of calcium-dependent PKC-alpha and calcium-independent PKC-epsilon isoforms in HTM and HCM. PKC-epsilon expression was more pronounced in HTM than in HCM. Similar PKC isoform expression was found in native bovine tissue. CONCLUSIONS: PKC isoforms show different tissue distributions in human and bovine TM and CM. Contractility differences exist in both tissues in response to PKC antagonists and agonists. The data indicate that PKC may be involved in regulation of aqueous humor outflow by the TM. Thus, inhibition of PKC may represent a new way of influencing outflow facility through isolated relaxation of TM.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1981

Argon laser goniophotocoagulation of the trabecular meshwork in open-angle glaucoma.

Argon laser goniophotocoagulation of the trabecular meshwork (ALGTM) after the method of Wise and Witter (1979) was performed on 66 eyes of 57 patients with phakic open-angle glaucoma. The duration of follow-up ranged from six to 21 months. The intraocular pressure decreased from a pre-treatment mean of 26.9 mm Hg to a post-treatment mean of 18.9 mm Hg and the mean number of medications used per eye decreased from 3.0 to 2.1 Of the 6 eyes, 54 (82%) were successfully controlled. The pressure-lowering effect was sustained rather than transient. The laser procedure was performed on an out-patient basis using only topical anesthesia. Complications were minimal in most cases. An early post-treatment rise in pressure greater than 6 mm Hg (range 7 mm Hg to 27 mm Hg) occurred in 14 eyes but two-thirds of this group were, nevertheless, successfully controlled. Failure did not adversely influence the outcome of subsequent glaucoma surgery.

Adolescent↗

PubMed2003

Permissive effect of fibronectin on collagen gel contraction mediated by bovine trabecular meshwork cells.

PURPOSE: The effect of fibronectin on the contractility of trabecular meshwork (TM) cells was investigated. METHODS: The contractility of bovine TM cells was evaluated by culture of the cells in a collagen gel and measurement of the change in the diameter of the gel under various conditions. The formation of stress fibers and the localization of integrin alpha5 and beta1 chains (which together form a fibronectin receptor) in bovine TM cells were investigated by laser confocal microscopy of cells stained with phalloidin and antibodies to the integrin subunits. RESULTS: The addition of fibronectin to collagen gels containing bovine TM cells induced marked gel contraction in a time- and concentration-dependent manner. Cytochalasin D (an inhibitor of microfilament formation) and the peptide GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro), a fibronectin receptor antagonist, each inhibited this effect of fibronectin, whereas nocodazole (an inhibitor of microtubule polymerization) and the control peptide GRGESP (Gly-Arg-Gly-Glu-Ser-Pro) did not. Furthermore, fibronectin induced the spreading of cells, the formation of actin stress fibers, and the expression of integrin alpha5 in the collagen gel-embedded TM cells. CONCLUSIONS: Fibronectin promotes collagen gel contraction mediated by bovine TM cells. Moreover, the formation of actin stress fibers and upregulation of integrin alpha5 appear to contribute to this permissive effect of fibronectin. The interaction of fibronectin with TM cells may thus be a determinant of the contractility of TM tissue.

Actins↗

PubMed1992

Age-related changes of sulfated proteoglycans in the normal human trabecular meshwork.

Ultrastructural changes in sulfated proteoglycans were studied in 12 pairs of normal eye-bank eyes (aged 1 day to 92 years), using the cationic dye, cuprolinic blue, in a 'critical electrolyte concentration'. Pretreatment of trabecular meshwork sections with various glycosaminoglycanases and nitrous acid served to characterize these proteoglycans. Three sizes of proteoglycan-cuprolinic blue (PG-CB) complexes were found in association with different extracellular matrix components. Small, thin PG-CB complexes were closely associated with collagen fibrils. Large, thick PG-CB complexes, although located close to collagen fibrils in a variety of places, were most commonly seen between the boundaries of the collagen bundles, where they were associated with fine filaments. Both types of collagen-associated PG-CB complexes contained chondroitin sulfate and dermatan sulfate, with dermatan sulfate predominant. Basal lamina-associated PG-CB complexes contained heparan sulfate. An age-related, progressive coalescence of collagen was found in normal trabecular meshwork in a statistically significant fashion; the regions of collagen coalescence were associated with a decrease of small, collagen-associated PG-CB complexes and an increase of a previously unrecognized matrix material. The measurement of areas of coalescence of collagen was used as an indirect indicator of small, collagen-associated PG-CB complex loss with age. Large collagen-associated PG-CB complexes and basal lamina-associated PG-CB complexes decreased from infant to young adult; no additional loss with age was found. Further studies will be needed to determine whether loss of sulfated PGs plays a role in increased aqueous outflow resistance that characterizes glaucoma.

Aging↗

PubMed2003

Cellular proliferative effect of dexamethasone in immortalized trabecular meshwork cell (TM5) line.

Dexamethasone (DEX), one of the corticosteroid hormones, is one of the most common therapeutic strategies in ophthalmological treatment. Despite its widespread use and clinical efficiency, little is known regarding the specific effects of DEX on cell growth, differentiation and cell death in human trabecular meshwork cells. The presence of the glucocorticoid receptor (GR, dexamethasone receptor) in TM-5 cell line, which was derived from the primary human trabecular meshwork cells, was verified by RT-PCR and western blot analysis. The effects of DEX on the cellular proliferation of TM5 cells were measured by a BrdU incorporation assay. Western blot analysis were used to examine the effects of DEX on the Ras/MEK/ERK signaling pathway. The total Ras, MEK1/2 and ERK1/2 protein levels as well as the levels of activated (phosphorylated) form were both significantly increased by the DEX treatment for 5 days. Both MEK1/2 and ERK1/2 were significantly activated by phosphorylation after 10 minutes. The dependence of this increased cell proliferation on GR activation by DEX and the sustained activation of ERK was examined using RU486 (a GR inhibitor) and U0126 (a MEK inhibitor). Both RU486 and U0126 prevented the induction of cell proliferation by the DEX treatment in the TM5 cells. In conclusion this study demonstrated that GR is expressed in TM5 cells. Secondly, DEX treatment for 5 days stimulates cell proliferation in TM5 cells, and that this increased proliferation effect is mediated by the Ras/MEK/ERK pathway.

Cell Division↗

PubMed1994

[Electron microscopic histochemical study in human trabecular meshwork--Second report: location of glycoconjugate residues using lectins].

The location of fourteen lectins in normal human trabecular meshworks were investigated with the electron microscope. The specimens were embedded in Lowicryl K4M at low temperature. Ultrathin sections were stained with biotin labeled lectins and colloidal gold labeled streptoavidin and observed with the electron microscope. ABA, ConA, DSA, PHA-E1, PHA-L4, WGA, LCA, and RCA120 were localized around fine fibrils underneath the endothelium of the trabecular wall of the Schlemm's canal (type I plaque) and collagenous fibers in the corneoscleral meshworks. ABA, ConA, and DSA were localized on the long-spacing collagens, basal membrane, microfibrils of elastic fiber (type II plaque), and fine granular (type III plaque). The present study indicated that extracellular matrices of normal human trabecular meshworks contained specific glycoconjugate residues.

Aged↗

PubMed2003

Low dose latrunculin-A inhibits dexamethasone-induced changes in the actin cytoskeleton and alters extracellular matrix protein expression in cultured human trabecular meshwork cells.

We determined the effects of a low dose of the actin-disrupting agent latrunculin (LAT)-A on dexamethasone (DEX)-induced changes in actin organization, focal adhesions, and production of extracellular matrix proteins in cultured human trabecular meshwork (HTM) cells. HTM cells were cultured to a highly confluent stage with stable endothelium-like morphology and incubated with 0.1 or 0.2 microM DEX and/or 0.1 microM LAT-A. Changes in the actin cytoskeleton and vinculin-containing focal contacts were evaluated by immunofluorescence microscopy. Expression of thrombospondin-1 (TSP1) and fibronectin (FN) in HTM cells was evaluated by Western blot analysis. The results showed that DEX induced morphological changes and actin reorganization in HTM cells. The cells partly recovered after DEX withdrawal, but the addition of low dose LAT-A hastened the recovery. In addition, DEX failed to induce changes when co-incubated with LAT-A for at least 4 weeks, and for at least 2 weeks when cells were pre-treated with LAT-A for 2 weeks. HTM cells treated with 0.1 microM LAT-A only for 5 days showed mild disorganization of the actin cytoskeleton and focal adhesions, which persisted during the 4 weeks of treatment. DEX stimulated production of FN in HTM cells independent of LAT-A treatment. LAT-A and, to a lesser extent, DEX inhibited production of TSP1 by HTM cells. Although LAT-A is not a DEX receptor antagonist, it is able to prevent the effects of DEX on the actin cytoskeleton in cultured HTM cells at a dose subthreshold for increasing outflow facility in monkeys. This suggests that LAT-A at low doses may be useful in treating steroid and other glaucomas. TSP1 may be an important target of LAT-A in HTM cells and modulation of TSP may influence the actin cytoskeleton of the trabecular meshwork (TM), and consequently, intraocular pressure.

Actins↗

PubMed1995

[Trabecular meshwork and elastin].

Evidence that elastic fibers with elastin exists in the trabecular meshwork (TM) and play an important role in aqueous outflow resistance is presented. The elastic fibers consist of abundant microfibrillar components containing glycoproteins and amorphous components containing elastin. If TM tissues are digested with elastase, the cells composing trabecular sheets and Schlemm's canal are separated with a decrease of elastin and come in contact with each other with reproduction of elastin. When the anterior segments of eyes are perfused with elastase, the intraocular pressure drops with a decrease of outflow resistance. A large quantity of elastin exists in fine fibrils lying underneath the trabecular wall of Schlemm's canal in primary open angle glaucoma (POAG) eyes, in pseudoexfoliation (PE) materials of PE glaucoma eyes and in basement membrane and fine fibril-like materials of steroid glaucoma eyes. In congenital and juvenile glaucoma eyes, however, instead of elastin, fibronectin localizes in basement membrane and fine fibril-like materials. When TM tissues respond to steroid hormone, the tissues synthesize and secret microfibrils and elastin, components of the elastic fibers. Elastin gene expresses in human TM. Orally administered elastase is transferred in aqueous humor and digests elastin in TM. Therefore it is possible that such a drug decreases the outflow resistance of glaucoma eyes.

Animals↗

PubMed1990

[Ablation of the trabecular meshwork].

In an experimental investigation we examined the possibility to create an open pathway between the anterior chamber and Schlemm's canal by excimer laser ablation of the trabecualr meshwork (AT) in enucleated eyes. A quartzfiber was directed through the anterior chamber to the opposite chamber angle. With an energy of 0.3-1.5 mJ and wavelengths of 248 and 308 nm pores were easily made into the trabecular meshwork leading to a direct connection between the anterior chamber and Schlemm's canal. This result was confirmed by histologic examination of the globes. The trabecular meshwork has disappeared completely. The surrounding tissue reveals only minimal thermal effects due to the laser burns. With the same method cyclodialysis and basal iridectomy may be performed. The operation is simple and effects can be placed with great accuracy.

Animals↗

PubMed1989

The effect of argon laser trabeculoplasty upon the normal human trabecular meshwork.

The effect of argon laser trabeculoplasty (ALT) upon the normal human trabecular meshwork, as determined by scanning and transmission electron microscopy is reported. The lower nasal and temporal quadrants of an eye received ALT 5 and 1 day, respectively, prior to enucleation. Laser impact sites were identified as focal disruptions of trabeculae, together with connective tissue and cellular debris. Surviving trabecular endothelial cells near the laser lesions exhibited signs of phagocytic and migratory activity. Exogenous macrophages also contributed to the clearance of debris. Activated trabecular cells were observed leaving the meshwork by migrating over the corneal endothelium. By 5 days post-ALT increased amounts of trabeculae lacked an endothelial covering. More activated trabecular cells but fewer macrophages were noted. A laser lesion sited close to Schwalbe's line induced, within 5 days, a local corneal endothelial wave front to advance towards it, thus reflecting many late failed ALT specimens that we have seen.

Humans↗

PubMed2003

The effect of TGF-beta2 on human trabecular meshwork extracellular proteolytic system.

Our study aimed to investigate whether transforming growth factor-beta2 (TGF-beta2), increased in the aqueous humor of eyes with primary open angle glaucoma (POAG), can affect factors responsible for the activity of matrix metalloproteinases (MMPs) in human trabecular cell cultures. With this goal in mind cultures of human trabecular meshwork (hTM) cells derived from 8 donors were treated with TGF-beta2 for 24, 36 and 48 hr. Influence of TGF-beta2 on expression of MMP-2, MMP-9, membrane type 1-MMP (MT1-MMP) and plasminogen activator inhibitor-1 (PAI-1) was examined using RT-PCR, Northern Blot, Western Blot and zymography. The influence of TGF-beta2 treatment on PAI-1 expression was also investigated using immunohistochemistry. It appeared that treatment with TGF-beta2 significantly increased expression of the proform of MMP-2, whereas the active form was not detectable. MMP-9 and MT1-MMP expression were not influenced by TGF-beta2 treatment. There was, however, a significant increase in PAI-1 expression. To investigate whether transformation of the proform of MMP-2 to the active form was inhibited by PAI-1, the influence of treatment with TGF-beta2 and a PAI-1 neutralizing antibody on MMP-2 was investigated using zymogram method. With this treatment protocol the active form of MMP-2 was clearly visible, indicating that TGF-beta2 enhancement of the PAI-1-expression decreases MMP activity. Inhibition of MMP activity through elevated levels of TGF-beta2 might contribute to the increase in ECM in the trabecular meshwork of glaucomatous eyes.

Adult↗

PubMed1994

Effects of antiglaucoma agents on glycosaminoglycans in organ-cultured rabbit trabecular meshwork.

The effect of antiglaucoma drugs on glycosaminoglycans (GAGs) of the rabbit trabecular meshwork (TM) was studied by organ culture and sequential enzymatic degradation (SED). Whole TM explants from one rabbit eye were dissected into 8 parts, then divided into control, epinephrine-, timolol- and pilocarpine-treated groups. After 2 weeks of culture, and incubation with medium containing radiolabeled precursors for 48 h, GAGs of the TM were isolated and subjected to SED. Treatment with epinephrine significantly reduced the hyaluronic acid and increased the chondroitin sulfate in radiolabeled precursor incorporation rate (p < 0.001). Other drugs had little effect. Thus, epinephrine appeared to influence the biosynthesis of GAGs of rabbit TM.

Animals↗

PubMed2005

Cochlin deposits in the trabecular meshwork of the glaucomatous DBA/2J mouse.

Cochlin deposits were observed in the trabecular meshwork (TM) of 8-month-old glaucomatous DBA/2J mice, coincident with the reported onset of increased intraocular pressure and optic nerve damage. An age-dependent increase in cochlin was observed up to 10 months of age and was paralleled by a decrease in type II collagen. Similar expression patterns exist in the TM of humans with primary open-angle glaucoma. Cochlin deposits, absent in non-glaucomatous mouse and human TM, may disrupt the TM extracellular matrix and obstruct aqueous humor circulation. Studies of DBA/2J mice offer promise for understanding the role cochlin may play in glaucoma.

Aging↗

PubMed1993

[Ultrastructural immunohistochemical localization of elastin in the human trabecular meshwork].

An electron microscopy study on the distribution of elastin in the trabecular meshwork of normal human eyes and in that of eyes with primary open angle glaucoma (POAG) was done using a protein-A gold immunohistochemical method with antiserum to either alpha-elastin or tropoelastin. Four types of elastic fibers were found to have elastin: (1) elastic-like fibers without the sheath, (2) fibers surrounded with a sheath of periodic structure, (3) fibers surrounded with fine granular-like material, and (4) connecting fibrils. No individual differences were observed in the labeling for these four types of elastic fibers. Antigenic sites against elastin of the elastic fibers were observed mainly in the low electron density amorphous elements. In the subendothelial layer of Schlemm's canal of the eyes with POAG, a marked increase of elastin was noted within the area containing fine fibrillar-like material. This phenomenon did not occur in age-matched normal eyes. The results suggest that elastin plays an important role in the development of POAG.

Elastin↗

PubMed2000

Isolation of primary open-angle glaucomatous trabecular meshwork cells from whole eye tissue.

PURPOSE: Isolation and culture of human trabecular meshwork (TM) cells from primary open-angle glaucomatous (POAG) tissue has proven difficult. The objective of this study was to directly compare the utility of two different isolation methods to obtain viable human TM cells from POAG whole eye tissue. METHODS: Using a blunt dissection technique, human TM tissue was obtained from four pairs of donor eyes (67, 77, 81 and 82 years) with a documented history of POAG. TM tissue from one eye was explanted into tissue culture. TM from the contralateral eye was digested with a collagenase mixture and seeded onto culture plates. RESULTS: Primary cell isolates were obtained from all donors with both techniques. However, only cells obtained using the digestion method (3 of 4 TMs) could be passaged for expansion and freeze-downs (3 x 107 second passage cells/donor). None of the cells obtained from explanted TMs could be passaged. Cells from successful isolations were of uniform size, possessed typical TM morphology and had doubling times < 48 hours. CONCLUSION: These results demonstrate a clear advantage to digesting the extracellular matrix of glaucomatous TM tissue to obtain sufficient numbers of healthy cells for use in experiments. In contrast to cells obtained from explants, cells liberated from POAG TM tissue by digestion appear indistinguishable morphologically and behaviorally from "normal" TM cells.

Aged↗

PubMed2003

Real-time direct measurement of nitric oxide in bovine perfused eye trabecular meshwork using a clark-type electrode.

NO was detected in bovine trabecular meshwork (TM). Bovine eyes were perfused (posterior ciliary artery). In some eyes (operated eyes) a NO electrode was inserted adjacent to the TM (scleral flap). Vascular perfusion/intraocular pressures (VPP/IOP) were recorded. In operated eyes, epinephrine (1 nM-100 microM) increased NO (maximally 979.9 +/- 117.6 nM, mean +/- SDM). Timolol (1 mM) shifted the epinephrine-NO concentration-response curve rightward (2.94 log units) without significantly changing the maximal response (903.0 +/- 67.7 nM, mean +/- SDM). The non-selective NO synthase (NOS) inhibitor L-NMMA (100 microM) virtually abolished the NO response to epinephrine. L-NMMA alone (1 microM-100 microM) significantly reduced tonic NO generation (maximally 109.5 +/- 24.9 nM, mean +/- SDM), whereas timolol alone (1 microM-1 mM) had no effect. In unoperated eyes, epinephrine (1 nM-100 microM) reduced IOP (maximally 2.56 +/- 0.64 mmHg, mean +/- SDM). Epinephrine (100 microM) mildly increased VPP (4.6 +/- 1.3 mmHg, mean +/- SDM). Baseline aqueous humor formation rate (11.5 +/- 3.2 microl/min, mean +/- SDM) was unaffected. Effluent perfusate (effusate) total NO(2)(-) was determined by enzymatically reducing all NO(3)(-) to NO(2)(-), then assessing resultant NO(2)(-) (Griess assay). Epinephrine (1 nM-1 microM) increased effusate NO(2)(-) (maximally 15.8 +/- 4.9 microM, mean +/- SDM). Timolol (1 mM) reduced, and L-NMMA (100 microM) virtually abolished effusate NO(2)(-) response to epinephrine. L-NMMA alone (1 microM-100 microM) reduced tonic effusate NO(2)(-) (maximally from 5.8 +/- 1.6 microM to 1.1 +/- 0.9 microM, mean +/- SDM), whereas timolol alone (1 microM-1 mM) had no effect. NO is generated tonically in bovine TM and increases in response to epinephrine.

Animals↗