Search PubMed⌕ Search

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.

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

At least 145 records · Page 8Linked to original sources
PubMed1995

Electron microscopic lectin histochemistry of the trabecular meshworks in human eyes.

Ten normal human trabecular meshworks were examined by electron microscopy using avidin-biotin complex in order to investigate the localization of binding sites of eight lectins. The tissue specimens were fixed in paraformaldehyde and glutaraldehyde mixture and embedded in Lowicryl K4M at low temperature. The ultrathin sections were stained with biotin labelled lectins and colloidal gold labelled streptoavidin and were observed with the conventional transmission electron microscope. Some lectins such as ABA, ConA and DSA were localized on fine fibrils underneath the endothelium of the trabecular wall of the Schlemm's canal, electron-dense cores of elastic fibers, fine granular like materials, basement membranes, collagen fibers and the long-spacing fibers. However, the other lectins such as DBA, SBA, Lotus, UEA-I and RCA60 were not specifically localized in these tissues. From the results it was demonstrated that the differential ultrastructural localization of glycoconjugate residues in the human trabecular meshworks can be revealed using this lectin staining.

Adult↗
PubMed2004

Genes expressed in the human trabecular meshwork during pressure-induced homeostatic response.

Physiological pressure inside the eye is maintained by a resistance mechanism provided by the trabecular meshwork tissue. In most cases, prolonged, elevated pressure leads to an eye pathology characterized by retinal ganglion cell (RGC) degeneration, optic nerve damage, and non-remedial blindness. We are investigating the regulation of trabecular meshwork genes in response to elevated pressure. Using perfused organ cultures from postmortem human donors, we have previously demonstrated the presence of a homeostatic mechanism at 2-4 days of pressure insult (Borrás et al. 2002, Invest Ophthalmol Vis Sci 43:33-40). Here, we sought to identify trabecular meshwork genes whose expression was altered during this homeostatic period. By macroarray hybridization, we compared the expression profiles of high-pressure (HP) and normal-pressure (NP) treated eyes from the same individual (n = 3 pairs). Our results identified 40 upregulated and 14 downregulated genes. The highest proportion of upregulated genes encoded proteins involved in signal transduction (32%). Among the potentially relevant genes, PIP 5K1C, VIP, tropomodulin, and MMP2 encoded mediators known to influence outflow resistance. Others encoded functions which are new for the trabecular meshwork, but which are intrinsic to unrelated tissues. These new mechanisms appear as they could be of benefit for trabecular meshwork function. Matrix Gla protein (MGP), perlecan, osteomodulin, and osteoblast-specific factor are essential in cartilage and bone physiology whereas spectrin and ICAM4 are specific for blood cells and crucial in maintaining their shape and adhesion. In addition, MGP transcripts were stimulated by extracellular calcium and downregulated by TGF-beta1. We propose that MGP might be an important player in the adaptive homeostatic mechanism by contributing to maintain a softer trabecular meshwork tissue and facilitate aqueous humor outflow.

Aged↗
PubMed2001

Cannabinoid CB(1) receptor expression, activation and detection of endogenous ligand in trabecular meshwork and ciliary process tissues.

Elevated intraocular pressure is the primary risk factor for glaucoma. Cannabinoids interact with molecular targets in the eye and lower intraocular pressure by an unknown mechanism. The purpose of the present study was to examine eye tissues for functional cannabinoid receptors of the neuronal, CB(1) class, and an endogenous ligand, anandamide. The trabecular meshwork and ciliary processes are the primary structures of the eye that contribute to intraocular pressure and thus were our focus. Total RNA, frozen sections, cellular membranes and primary cultures of cells were prepared from both bovine and cadaveric human tissues. Using cannabinoid CB(1) receptor-specific oligodeoxynucleotide primers, cannabinoid CB(1) receptor antiserum, and cannabinoid-specific compounds (CP-55,940, WIN55,212-2 and SR-141716A), the presence of cannabinoid CB(1) receptors in ciliary processes and trabecular meshwork was determined. Using reverse transcription-polymerase chain reaction, we identified mRNA encoding cannabinoid CB(1) receptor protein in ciliary process and trabecular meshwork cells. Specific binding of anti-CB(1) immunoglobulin-G in tissue sections localized cannabinoid CB(1) receptor protein to the non-pigmented epithelial cells of the ciliary process and cells of the trabecular meshwork. While CP-55,940 and WIN55,212-2 failed to stimulate [(35)S]GTP gamma S binding in membrane preparations from trabecular meshwork and ciliary process, CP-55,940 significantly stimulated whole cell [(35)S]GTP gamma S binding by 51% over basal in ciliary process epithelial cells and 69% over basal in trabecular meshwork cells permeabilized with 5 microM digitonin (p<0.001). Specificity of agonist stimulation was verified by complete blockade with the specific cannabinoid CB(1) receptor antagonist, SR-141716A. Moreover, activation of cannabinoid CB(1) receptors by CP-55,940 resulted in a 2.3+/-0.3 and 1.7+/-0.3-fold stimulation of cAMP accumulation in trabecular meshwork and ciliary process cells, respectively (p<0.01). Lastly, anandamide was detected in human trabecular meshwork (3.08 pmol/g), ciliary process (49.42 pmol/g) and neurosensory retinal (4.48 pmol/g) tissues. These data, for the first time, demonstrate in a single study the presence of both CB(1) mRNA and protein in trabecular meshwork and ciliary processes from two different species. Activation of heterotrimeric G-proteins and stimulation of cAMP accumulation by cannabinoids in vitro suggest that their intraocular pressure-lowering effects in vivo result from activation of cannabinoid CB(1) receptors in the trabecular meshwork and increase aqueous outflow.

Animals↗
PubMed2004

Cell volume response to hyposmotic shock and elevated cAMP in bovine trabecular meshwork cells.

PURPOSE: Hyposmolar perfusion of intact trabecular meshwork (TM) induces a decrease in its hydraulic conductivity (Lp). However, exposure to agents that elevate intracellular cAMP in TM cells increases Lp. Since volume of TM cells could directly influence porosity of the TM and hence Lp, this study has investigated changes in volume in response to acute hyposmotic shock (i.e. regulatory volume decrease or RVD) and elevated cAMP in cultured TM cells. METHODS: Bovine trabecular meshwork cells (BTMC), grown on glass coverslips and loaded with the fluorescent dye MQAE, were used to measure rapid changes in cell volume using the principle of dynamic fluorescence quenching. Activation of volume-regulated anion channels (VRAC) was assessed by measuring volume-sensitive Cl(-) currents (I(Cl,swell)) in the whole cell configuration of the patch clamp technique and by determining the swelling-induced enhancement in I(-) permeability using the halide-sensitivity of MQAE. Expressions of ClC (chloride channels of the ClC gene family), P-glycoprotein (Pgp), and cystic fibrosis transmembrane regulator (CFTR) Cl(-) channels were examined by RT-PCR. Elevation of cAMP in response to forskolin was confirmed by determining the phosphorylation of cAMP response element-binding protein and activating transcription factor-1 (CREB, ATF-1), which form the downstream targets of protein kinase A. RESULTS: As a response to hyposmotic shock, there was an acute increase in cell volume but there was no robust RVD. Patch clamp experiments showed activation of a characteristic Cl(-) current in response to cell swelling. This Cl(-) current was inhibited by NPPB (100microM) and fluoxetine (50microM), both of which are known blockers of VRAC. Experiments, which used the halide-sensitivity of MQAE, also indicated a 9-fold increase in I(-) influx upon cell swelling (8.9+/-4.6; n=9), consistent with activation of a VRAC-like Cl(-) current. To examine whether RVD is limited by K(+) conductance, the swollen cells were exposed to gramicidin, which is known to induce cation channel activity. Such a maneuver led to secondary swelling with [Na(+)](o)=140mM but a rapid shrinkage [Na(+)](o)=8mM indicating that the RVD is limited by cationic conductance necessary for K(+) efflux. Exposure to forskolin, which resulted in CREB and ATF-1 phosphorylation, caused a reversible decrease in cell volume (14.5+/-5%; n=20) under isosmotic and hyposmotic conditions. RT-PCR analysis confirmed expression of ClC-2, ClC-5, and Pgp Cl(-) channels in bovine TM cells. However, ClC-3 and CFTR were not expressed. CONCLUSIONS: TM cells respond to acute hyposmotic shock in an osmometric manner, but their RVD is limited by K(+) conductance. The lack of CFTR expression and decrease in cell volume in response to forskolin concomitant with hyposmolarity suggest that elevated cAMP activates a K(+) conductance. Thus, the altered resistance to aqueous outflow in response to hyposmotic perfusion of the TM and elevated cAMP may be attributed to persistent cell swelling and cell shrinkage, respectively.

Animals↗
PubMed1997

[Expression of proteinase inhibitors in the human trabecular meshwork].

We examined the distribution and expression of three proteinase inhibitors, alpha 1-proteinase inhibitor (alpha 1-PI), alpha 1-antichymotrypsin (alpha 1-ACT), and alpha 2-macroglobulin (alpha 2-M) in the human trabecular meshwork. Immunohistochemistry, in situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) were used. By immunostaining, all three inhibitors were identified in the human trabecular meshwork with enhanced staining in the uveal meshwork. In situ hybridization showed mild but positive accumulation of the silver grains on the trabecular meshwork cells, which indicates mRNA expression. Specific distribution or cell selectivity were not detectable probably due to weak expression of these inhibitors in this tissue. Instead mRNAs for alpha 1-PI, alpha 1-ACT, and alpha 2-M as well as antithrombin III, plasminogen activator inhibitor-1 could be identified by RT-PCR using trabecular meshwork culture cells. In this study, we concluded that some proteinase inhibitors were distributed in the human trabecular meshwork as well as in the cornea and the ciliary body. At least part of these were probably produced by the trabecular meshwork cells. The balance between proteinases and proteinase inhibitors might play an important role even in the human trabecular meshwork to maintain the outflow route. The alterations in the primary or secondary glaucomatous eyes are curious.

Adolescent↗
PubMed1997

Proteoglycan expression by human trabecular meshworks.

PURPOSE: Proteoglycans may serve important roles in trabecular meshwork structure or function. Detailed molecular characterization and identification of specific trabecular proteoglycan core proteins has been limited. METHODS: Radiolabeled proteoglycans were extracted from cultured human trabecular meshworks and subjected to ion exchange and molecular sieve chromatography. Peaks were subjected to glycosaminoglycan content analysis. Reverse transcription with polymerase chain reaction was used to identify trabecular mRNAs of several common proteoglycan core proteins. Western immunoblots of trabecular extracts were also utilized to identify these proteoglycan core proteins. RESULTS: The proteoglycans elute from ion exchange columns at high salt and molecular sieve column profiles, and they exhibit broad peaks typical of the proteoglycan microheterogeneity seen in other tissues. The four common glycosaminoglycan side-chains were identified on these proteoglycans. Trabecular cells in organ or cell culture contain mRNAs coding for decorin, biglycan, versican, perlecan and a basement membrane glycoprotein, SPARC. Syndecan-1 transcripts were present at very low levels, while aggrecan transcripts were not detectable. Decorin, biglycan, versican and perlecan core proteins were also identified by immunoblots of trabecular cell extracts. CONCLUSIONS: Several common proteoglycans are expressed by trabecular cells in organ explant or cell culture. Their general characteristics are not unlike those found in other tissues. These proteoglycans may serve important functions in the trabecular outflow pathway.

Aggrecans↗
PubMed1992

Effects of endothelin and calcium channel blockers on membrane voltage and intracellular calcium in cultured bovine trabecular meshwork cells.

The membrane voltage was measured in cultured bovine trabecular meshwork cells. External barium (Ba2+; 10 mM) evoked repetitive overshooting action potentials which were reversibly inhibited by 10(-6) M nifedipine but insensitive to tetrodotoxin (10(-5) M). In contrast, no action potentials could be induced in bovine corneal endothelial cells. The vasoactive peptide endothelin (10(-9)-10(-6) M) induced dose-dependent depolarizations. The intracellular calcium concentration measured by the fura-2 method increased after endothelin application. An initial peak was followed by a sustained plateau. The effect of endothelin on the membrane potential and intracellular calcium value is typical for smooth muscle cells showing a contractile response to the peptide. Recent studies have shown the contractility of bovine trabecular meshwork. We conclude that calcium-channel antagonists and endothelin may alter the aqueous humour outflow through the trabecular meshwork.

Animals↗
PubMed2004

Gene and protein expression changes in human trabecular meshwork cells treated with transforming growth factor-beta.

PURPOSE: To determine the genomic and proteomic expression changes in human trabecular meshwork cells when they are treated with transforming growth factor (TGF)-beta. METHODS: Human trabecular meshwork cells from five donors were cultured for 3 days with 1 ng/mL of either TGF-beta1 or -beta2. Changes in gene expression determined with gene microarrays and alterations in protein expression detected by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) were studied in these cells after the incubation. RESULTS: With both TGF-betas, there was a substantial upregulation of genes that were related to secreted proteins or extracellular matrix. This result was consistent with pathologic changes observed in disease and with experiments on perfused trabecular meshwork. Several of the gene changes suggest that other signaling pathways, such as ErbB and Wnt, were altered. Changes in enzyme expression in the prostaglandin pathway indicated that the prostaglandins may have a different cellular profile in the presence of glaucoma. Two genes, osteoblast-specific factor 2 and corneal-derived transcript 6, which are highly expressed in the cells under normal conditions, were substantially upregulated with the TGF-betas. Proteomic analysis indicated that there was increased proteolysis of vimentin with both treatments. Tropomyosin 1alpha was increased in both gene and protein expression, suggesting alterations of the cytoskeleton by the disease. The TGF-beta1 treatment caused more robust changes than those induced by TGF-beta2. Three genes-aldose reductase, thioredoxin reductase 1, and glucose-6-phosphate 1-dehydrogenase-were identified that were downregulated in expression. These genes had decreases in protein expression with TGF-beta1 treatment but had little change in either gene or protein expression with TGF-beta2. CONCLUSIONS: Human trabecular meshwork cells can be subjected to increased levels of TGF-beta for several years as a result of glaucoma. The results indicate that changes in extracellular matrix as well as alterations in cytoskeletal proteins occur in these cells as a result of increased TGF-beta. These results are consistent with changes observed in the trabecular meshwork in glaucoma and suggest that at least some of the histologic alterations observed in the meshwork in glaucoma may be the result of increased TGF-betas.

Adolescent↗
PubMed2003

Elevation of nitric oxide production in human trabecular meshwork by increased pressure.

BACKGROUND: The presence of the nitric oxide (NO)-producing enzyme nitric oxide synthase (NOS) in the trabecular meshwork and the effect of various drugs acting through the NO pathway on the outflow facility and trabecular contractility suggest a role for NO in the regulation of outflow and intraocular pressure (IOP). METHODS: To model the effect of elevated IOP on the NO production in the trabecular meshwork, we perfused anterior segments of human donor eyes in vitro and studied the effect of raised perfusion pressure on NO levels in the perfusate. Furthermore, we evaluated using quantitative PCR whether enhanced perfusion pressure had an effect on the NOS gene expression levels. RESULTS: Elevating the pressure from 10 mmHg to 25 mmHg caused a significant increase in NO production from 3.6+/-0.9 pmol/min to 5.9+/-1.6 pmol/min (mean +/- SEM), corresponding to an average increase of 66%. These high NO levels were reduced by application of L-NAME, an NOS inhibitor, to 2.6+/-0.6 pmol/min. Addition of L-NAME before raising the pressure decreased the basal NO production but was not able to block the increase in NO production after raising the pressure. The transcript level of iNOS was significantly increased in the trabecular meshwork after raising the perfusion pressure. CONCLUSION: These results show that NO production increased after elevation of the pressure gradient over the trabecular meshwork, accompanied by an upregulation of iNOS gene expression. Previous studies have demonstrated that enhanced NO levels facilitate outflow. Taken together, the data indicate the existence of a regulatory feedback mechanism in the trabecular meshwork, which may contribute to the regulation of the IOP. In this system an increase in IOP will enhance NO production, which, in turn, increases the outflow facility, leading to a normalization of the IOP.

Aged↗
PubMed2003

Donor corneoscleral buttons: a new source of trabecular meshwork for research.

The human trabecular meshwork (TM) is the major site of resistance for aqueous humor outflow. The purpose of this investigation was to determine the suitability of TMs harvested from donor corneoscleral buttons (buttons) for laboratory studies. Histologic examination using light and electron microscopy was performed. Additionally, the effect of incubation in serum free media on histologic appearance was studied. Total RNA extraction was performed on 45 buttons and four whole eyes. Some TMs were used as a source for establishing primary cell cultures of TM endothelial cells. Compared with donor whole eyes, light microscopy showed comparable TM cellularity in the juxtacanalicular and corneoscleral TM; there was some loss of cells in the inner portion of uveal TM that was adjacent to the anterior chamber. The TM cells appeared healthy and structurally normal on transmissive electron microscopy. Usable quantities of total RNA could be extracted from buttons that had been stored up to 5 weeks. The amount of total RNA extracted correlated well with the histologic appearance. Incubation in serum free media did not have an effect on the histologic appearance. All attempts at establishing primary cell cultures were successful. Unused, donor corneoscleral buttons are an excellent source of TM.

Adult↗
PubMed2006

Identification and functional characterization of ClC-2 chloride channels in trabecular meshwork cells.

In the eye, trabecular meshwork (TM) cell volume may be an important determinant of aqueous humor outflow. Among their functions, ClC-2 chloride channels are thought to be involved in regulation of cellular volume and intracellular [Cl(-)]. We characterized the properties and modulation of an inwardly rectifying chloride current activated in these cells. Patch-clamp recordings revealed inwardly rectifying chloride currents activated by membrane hyperpolarization in primary cultures of both bovine (BTM) and human (HTM) TM cells. Electrophysiological properties and anion permeability sequence (Cl(-)>Br(-)>I(-)>F(-)) were in agreement with previous data for ClC-2 in other cells. The currents were blocked by Cd(2+) and enhanced by extracellular acidification, 8Br-cAMP and cell swelling, while extracellular alkalinization decreased them. RT-PCR experiments using total RNA revealed the molecular expression of ClC-2 channels. Previously we reported the involvement of swelling-activated chloride channels (Cl(swell)) and Ca(2+)-activated K(+) channels (BK(Ca)) in cell volume and outflow facility regulation. However, in the present analysis, cell volume experiments in calcein-loaded cells and outflow facility studies performed in bovine anterior segments revealed that ClC-2 channels do not make a significant contribution to the recovery of cellular volume or to the regulation of the outflow facility. Nevertheless, ClC-2 modulation by different stimuli may contribute to intracellular [Cl(-)] regulation and other cellular functions yet to be determined in the TM.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

Preliminary characterization of a transformed cell strain derived from human trabecular meshwork.

Cells isolated from the trabecular meshwork (TM) of a male glaucoma patient were transformed by transfection with an origin defective mutant of SV40 virus. Transformation dramatically increased the growth rate of these cells (designated HTM-3 cells), allowing biochemical and pharmacological characterization. The HTM-3 cells had cytoskeletal components that were reported to be present in TM tissue and non-transformed TM cells. Vimentin, tubulin and smooth muscle specific alpha-actin, but not desmin, were localized in these cells by immunocytochemistry. The extracellular matrix components collagen types I, III and IV, fibronectin and laminin were found in HTM-3 cells as well as their non-transformed parental cells. As predicted, the protein profile of the HTM-3 cells revealed by two-dimensional gel electrophoresis was different from that of the non-transformed cells, probably due to the enhanced growth characteristics of these cells. Furthermore, HTM-3 cells had various intracellular second messenger systems that responded to pharmacological agents. Forskolin, prostaglandin E2, beta-adrenergic and adenosine A2 agonists stimulated the adenylyl cyclase in these cells, whereas muscarinic, serotonergic, dopaminergic and other agonists were ineffective. Sodium nitroprusside increased the intracellular concentration of cGMP, demonstrating the presence of a functional guanylyl cyclase. Phospholipase C activity in these cells was also detected. Muscarinic agonists, histamine and bradykinin, but not adrenergic, serotonergic agonists or prostaglandins, increased phosphoinositide turnover. These drug responses of HTM-3 cells agree with published data on primary TM cells and TM tissues, suggesting that the transformed cells may be a valid substitute for certain pharmacological studies of TM.

Aged↗
PubMed1996

Adhesion of human trabecular meshwork cells to extracellular matrix proteins. Roles and distribution of integrin receptors.

PURPOSE: To examine the adhesion of human trabecular meshwork cells with various extracellular matrix (ECM) proteins and to evaluate the roles and distribution of integrin receptors. METHODS: Cultured human trabecular meshwork cells were added to 96-well plates either uncoated or coated with proteins including fibronectin, laminin, and vitronectin, as well as collagen types I, III, IV, V, and VI. After incubation for 1 hour, the adhesion of cells was measured. Expression of cell surface integrins was determined by cell enzyme-linked immunoadsorbent assay (ELISA) and immunoprecipitation. Distribution was visualized by immunofluorescence staining using integrin-specific antibodies. For function perturbation and peptide inhibition studies, cells were preincubated with either integrin antibodies or synthetic peptides before the adhesion assays. RESULTS: Human trabecular meshwork cells attached to plates coated with ECM proteins in a dose-dependent manner. Fibronectin, vitronectin, and collagen types I and IV were the preferred ECM substrates. Cell ELISA revealed the presence of integrins alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, alpha v, beta 1, beta 3, beta 5, alpha 5 beta 1, and alpha v beta 3 and the absence of beta 2 and beta 4 on human trabecular meshwork cells. Results from immunostaining experiments were consistent with those from cell ELISA studies. Attachment of cells to ECM proteins was blocked by specific integrin antibodies. Cell adhesion to fibronectin and vitronectin was inhibited by peptides containing the Arg-Gly-Asp sequence. CONCLUSIONS: Extracellular matrix proteins mediate the adhesion of human trabecular meshwork cells in culture. Integrin receptors appear to have functional roles in the cell-matrix interactions.

Adolescent↗
PubMed2004

Modulation of aqueous humor outflow by ionic mechanisms involved in trabecular meshwork cell volume regulation.

PURPOSE: Trabecular meshwork (TM) cell shape, volume, contractility and their interactions with extracellular matrix determine outflow facility. Because cell volume seems essential to TM function, this study was conducted to investigate further the ionic channels and receptors involved in regulatory volume decrease and their roles in modulating outflow facility. METHODS: Primary cultures of bovine TM cells were used. K(+) and Cl(-) currents were studied with whole-cell patch clamping. Swelling was induced by hypotonic shock. [Ca(2+)](i) was measured in TM cells loaded with fura-2. Bovine anterior segments were perfused at constant pressure to measure outflow facility. RESULTS: Hypotonic media activated both the high-conductance Ca(2+)-activated K(+) channel (BK(Ca)) and swelling-activated Cl(-) channel (Cl(swell)) currents and induced release of adenosine 5'-triphosphate (ATP) from TM cells. ATP activated P2Y(2) receptors with the following profile: ATP = uridine 5'-triphosphate (UTP) > adenosine 5'-O-(3-thiotriphosphate) (ATP-gamma S) > adenosine 5'-diphosphate (ADP) = uridine 5'-diphosphate (UDP), and increased BK(Ca) current. Hypotonic medium initially decreased outflow facility in perfused anterior segments, which recovered with time to baseline levels. Addition of tamoxifen or iberiotoxin (Cl(swell) and BK(Ca) blockers, respectively) lengthened the recovery phase, which implies that these channels participate in cell volume regulation. In contrast, an activator of BK(Ca)s (NS1619) produced the opposite effect. CONCLUSIONS: Cell swelling activates a regulatory volume decrease mechanism that implies activation of K(+) and Cl(-) currents and participation of P2Y(2) receptors. Because previous studies have shown that intracellular volume of TM cells is an important determinant of outflow facility, it seems feasible that cell volume regulation would be part of the homeostatic mechanisms of the TM, to regulate the outflow pathway.

Adenosine Triphosphate↗
PubMed1991

Expression of modified low-density lipoprotein receptors by trabecular meshwork cells.

We examined the incorporation of fluoresceinated low-density lipoprotein (LDL) and acetylated or acetoacetylated low-density lipoprotein (A-LDL or AA-LDL) by a number of ocular cells in culture. All the cells investigated, including bovine, monkey, human trabecular meshwork cells, human corneal endothelial cells, human corneal stromal cells and human scleral cells, took up fluorescently labeled LDL. The bovine, monkey and human trabecular meshwork cells showed the strongest fluorescence reactions. In addition, we found that the trabecular meshwork cells became fluorescent after incubations with labeled A-LDL or AA-LDL. They were the only cell type examined that possessed this capacity. The fluorescence intensity was markedly diminished by adding to the incubation solution either fucoidin, a competitive inhibitor of modified LDL uptake, unlabeled A-LDL or AA-LDL. The trabecular meshwork cells in situ also became brightly labeled after exposure to fluoresceinated native LDL, A-LDL or AA-LDL. The uptake of modified LDL separated the trabecular meshwork cells from other types of ocular cells, which may be used to aid identification of trabecular meshwork cells in culture as well as in situ. This property also suggested that trabecular meshwork cells may have some functional similarities to macrophages.

Acetylation↗
PubMed1997

Prostaglandin effects on the contractility of bovine trabecular meshwork and ciliary muscle.

The ocular hypotensive activity of prostaglandins (PGs) has previously been demonstrated in various species including man. The underlying mechanism of action of prostanoids other than PGF2 alpha remains contentious. Because the trabecular meshwork and ciliary muscle are believed to have a role in the regulation of aqueous humor outflow, the aim of this study was to identify the PG-receptor subtypes present in these tissues using receptor-selective agonists. Contractions of isolated strips of bovine trabecular meshwork and ciliary muscle were recorded isometrically in continuously perfused tissue chambers. Contractile activity of PGs was determined relative to a maximally effective concentration of carbachol (1 microM) as a standard agonist. The following prostanoids were employed: PGF2 alpha, 17-phenyl PGF2 alpha (FP-receptor agonists), sulprostone (EP3 > EP1-agonist), AH13205 (EP2-agonist), 11-deoxy PGE1 (non-selective EP-agonist), and U-46619 (TP-agonist). The thromboxane-mimetic U-46619 elicited a strong contraction of the trabecular meshwork with the highest concentration (1 microM) being almost twice as efficacious (186.6%) as the maximal carbachol concentration, whereas the effect on the ciliary muscle was small. The U-46619 induced trabecular meshwork contraction could be blocked with a potent and selective TP-receptor antagonist, 1 microM SQ29548, indicating the involvement of TP-receptors. The other PG-analogs studied had either no or a small but statistically significant effect. Thus, 17-phenyl PGF2 alpha (1 microM) weakly contracted the ciliary muscle (4.8%), sulprostone (1 microM) the trabecular meshwork (10.1%), 11-deoxy PGE1 (1 microM) and AH13205 (10 microM) elicited relaxations in both tissue precontracted with carbachol (1 microM). The relaxant effects were more pronounced in trabecular meshwork (15.6% for 11-deoxy PG1 and 21.4% for AH13205) than ciliary muscle (6.8 and 7.4% respectively). PGF2 alpha did not elicit a significant response in either tissue. Our studies suggest the existence of TP- and EP2-receptors in the bovine trabecular meshwork and potentially FP- and EP2-receptors in the ciliary muscle. In conclusion, thromboxane-mimetics and EP2-agonists have opposing activities on contractile elements in the meshwork and may modulate trabecular outflow in a functionally antagonistic manner. Prostanoid effects on ciliary muscle appear rather modest compared to parasympathomimetic drugs. It is conceivable that TP-agonists may substantially affect trabecular outflow.

Animals↗
PubMed2000

mRNA in situ hybridization of TIGR/MYOC in human trabecular meshwork.

PURPOSE: To determine the distribution of mRNA expression of the trabecular meshwork-induced glucocorticoid response protein/myocilin (TIGR/MYOC) in human trabecular meshwork. METHODS: In situ hybridization using a 1.25-kb probe obtained from reverse transcription-polymerase chain reaction of TIGR/MYOC cDNA was performed to determine the location of cell labeling within the different regions of the meshwork. The effect of dexamethasone on the pattern of labeling was studied in organ cultured meshwork. Trabecular meshwork from three sources was studied: enucleated eyes obtained at autopsy, trabeculectomy specimens obtained during filtration surgery, and meshworks from anterior segments in perfusion organ culture. Hybridization was performed on frozen sections, paraffin sections, and sections from JB-4 plastic-embedded tissue. RESULTS: Labeling for TIGR/MYOC mRNA was present in most trabecular cells of the uveal, corneoscleral, and juxtacanalicular regions but only variably present in the endothelial cells of Schlemm's canal. A similar pattern was found in the trabeculectomy specimens from eyes with primary open-angle or pseudoexfoliative glaucoma. Dexamethasone treatment increased the labeling intensity and number of labeled cells in meshwork, and also the number of labeled endothelial cells of Schlemm's canal. Fresh tissue processed within 12 hours postmortem gave more consistent labeling than older tissue, although some label was found up to 48 hours postmortem. Labeling was found in tissue from all three sources, and with all three embedding techniques; JB-4 sections provided the best morphologic resolution. CONCLUSIONS: In situ hybridization reveals that mRNA expression for TIGR/MYOC is present in most cells in all regions of the meshwork but only variably present in the endothelial cells of Schlemm's canal. Dexamethasone treatment increased the number and intensity of labeled cells, and also increased the number of labeled cells in the endothelial lining of Schlemm's canal.

Aged↗
PubMed2002

Aquaporin-1 expressed in cultured human trabecular meshwork cells.

OBJECTIVE: To determine if aquaporin-1 could be detected in cultures of human trabecular meshwork cells. METHODS: Using primers specific for aquaporin-1, reverse transcription combined with polymerase chain reaction (RT-PCR) yielded a product and its size with total RNA prepared from the human trabecular meshwork cells. SDS-PAGE and immunoblotting were also used in this study to detect the specific water channel. RESULTS: The presence of this product and its size (298 base pairs) are consistent with that of an aquaporin-1 message in these cells. A band of 28 kD in agreement with the molecular size of aquaporin-1 was showed in a film by immunoblotting. CONCLUSION: The presence of aquaporin-1 in human trabecular meshwork cells, the predominant cell-type of the primary outflow region of the human eye, suggests that water channels may be involved in the movement of aqueous fluid out of the eye. In addition, the existence of aquaporin-1 on cultures of human trabecular meshwork cells provides an in vitro model to study the endogenous expression of aquaporin-1 and its possible role in the regulation of aqueous outflow.

Aquaporin 1↗