The Role and Mechanism of Nicotinamide Riboside in Oxidative Damage and a Fibrosis Model of Trabecular Meshwork Cells

Purpose

To investigate the potential effects and mechanism of nicotinamide riboside (NR) on the oxidative stress and fibrosis model of human trabecular meshwork (HTM) cell line cells.

Methods

HTM cells were pretreated with NR, followed by the induction of oxidative injury and fibrosis by hydrogen peroxide (H2O2) and TGF-β2, respectively. Cell viability was tested using Hoechst staining and MTT assays, cell proliferation was assessed by EdU assay, and cell apoptosis was detected by flow cytometry and western blotting. DCFH-DA and DHE probes were used to measure the level of reactive oxygen species (ROS), and MitoTracker staining was used to measure the mitochondrial membrane potential (MMP). Fibrotic responses, including cell migration and deposition of extracellular matrix (ECM) proteins, were detected via Transwell assays, qRT-PCR, and immunoblotting.

Results

NR pretreatment improved the viability, proliferation, and MMP of H2O2-treated HTM cells. Compared to cells treated solely with H2O2, HTM cells treated with both NR and H2O2, exhibited a reduced rate of apoptosis and generation of ROS. Compared with H2O2 pretreatment, NR pretreatment upregulated expression of the JAK2/Stat3 pathway but inhibited mitogen-activated protein kinase (MAPK) pathway expression. Moreover, 10-ng/mL TGF-β2 promoted cell proliferation and migration, which were inhibited by NR pretreatment. Both qRT-PCR and immunoblotting showed that NR inhibited the expression of fibronectin in a TGF-β2-induced fibrosis model.

Conclusions

NR has a protective effect on oxidative stress and fibrosis in HTM cells, which may be related to the JAK2/Stat3 pathway and MAPK pathway.

Translational Relevance

Our research provides the ongoing data for potential therapy of NAD+ precursors in glaucoma.

Apoptosis inhibitor of macrophages/CD5L enhances phagocytosis in the trabecular meshwork cells and regulates ocular hypertension

The trabecular meshwork (TM) cells of the eye are important for controlling intraocular pressure (IOP) and regulating outflow resistance in the aqueous humor. TM cells can remove particles and cellular debris by phagocytosis, decreasing both outflow resistance and IOP. However, the underlying mechanisms remain unclear. Here, we investigate whether apoptosis inhibitor of macrophages (AIM), which mediates the removal of dead cells and debris in renal tubular epithelial cells, regulates the phagocytic capacity of TM cells. In vitro experiments revealed that CD36, the main receptor for AIM, colocalized with AIM in human TM cells; additionally, phagocytosis was stimulated when AIM was provided. Furthermore, in a mouse model with transient IOP elevation induced by laser iridotomy (LI), removal of accumulated iris pigment epithelial cells or debris in the TM and recovery of IOP to baseline levels were delayed in AIM-/- mice, compared with control mice. However, treatment with AIM eyedrops rescued AIM-/- mice from the elevated IOP after LI. Since AIM is a protein known to inhibit macrophage apoptosis, we additionally verified its involvement in macrophage removal of cellular debris and IOP. There were no statistically significant differences in the number of macrophages between control mice and AIM-/- mice in the TM. Additionally, we confirmed the rescue effect of the rAIM eyedrops after macrophages had been removed by clodronate liposomes. Therefore, AIM plays an important role in regulating the phagocytic capacity of TM cells, thereby affecting outflow resistance. Our results suggest that drugs targeting the phagocytic capacity of TM cells via the AIM-CD36 pathway may be used to treat glaucoma.

Activation of Sonic Hedgehog Signaling Pathway Regulates Human Trabecular Meshwork Cell Function

Purpose: To investigate the effects of Sonic hedgehog (Shh) signaling on primary human trabecular meshwork (HTM) cells. Methods: Primary HTM cells were isolated from healthy donors and cultured. Recombinant Shh (rShh) protein and cyclopamine were used to activate and inhibit the Shh signaling pathway, respectively. A cell viability assay was performed to assess the effects of rShh on the activity of primary HTM cells. Functional assessment of cell adhesion and phagocytosis was also performed. The proportion of apoptotic cells was examined using flow cytometry. Fibronectin (FN) and transforming growth factor beta2 (TGF-β2) protein were detected to assess the influence of rShh on the metabolism of the extracellular matrix (ECM). Real-time polymerase chain reaction (RT-PCR) and western blot analyses were used to examine mRNA and protein expression of Shh signaling pathway-associated factors GLI Family Zinc Finger 1 (GLI1) and Suppressor of Fused (SUFU). Results: rShh significantly enhanced primary HTM cell viability at a concentration of 0.5 μg/mL. rShh increased the adhesion and phagocytic abilities of primary HTM cells, and decreased cell apoptosis. FN and TGF-β2 protein expression increased in primary HTM cells treated with rShh. rShh upregulated the transcriptional activity and protein levels of GLI1, and downregulated those of SUFU. Correspondingly, the rShh-induced GLI1 upexpression was partially blocked by pretreatment with the Shh pathway inhibitor cyclopamine at a concentration of 10 μM. Conclusions: Activation of Shh signaling can regulate the function of primary HTM cells through GLI1. Regulation of Shh signaling may be a potential target for attenuating cell damage in glaucoma.

A Comparative Genome-Wide Transcriptome Analysis of Glucocorticoid Responder and Non-Responder Primary Human Trabecular Meshwork Cells

Aim: To investigate genes and pathways involved in differential glucocorticoid (GC) responsiveness in human trabecular meshwork (HTM) cells using RNA sequencing. Methods: Using paired human donor eyes, human organ-cultured anterior segment (HOCAS) was established in one eye to characterize GC responsiveness based on intra ocular pressure (IOP) change and, in the other eye, primary HTM cell culture was established. For RNA sequencing, total RNA extracted from GC-responder (GC-R) and non-responder (GC-NR) cells after dexamethasone (DEX) or ethanol (ETH) treatment for 7d was used. Differentially expressed genes (DEGs) were compared among five groups and validated. Results: In total, 616 and 216 genes were identified as significantly dysregulated in Group #1 and #2 (#1: ETH vs. DEX-treated GC-R; #2: ETH vs. DEX-treated GC-NR), respectively. Around 80 genes were commonly dysregulated in Group #3 (overlapping DEGs between #1 and #2), whereas 536 and 136 genes were uniquely expressed in GC-R (#4) and GC-NR HTM (#5) cells, respectively. Pathway analysis revealed that WNT signaling, drug metabolism cytochrome p450, cell adhesion, TGF-β signaling, and MAPK signaling were associated with GC responsiveness. Conclusion: This is the first study reporting distinct gene signatures and their associated pathways for GC-R and GC-NR HTM cells. WNT and MAPK signaling are potential therapeutic targets for the management of GC-induced glaucoma.

SNHG3 cooperates with ELAVL2 to modulate cell apoptosis and extracellular matrix accumulation by stabilizing SNAI2 in human trabecular meshwork cells under oxidative stress

Glaucoma is the main reason for irreversible blindness, and pathological increased intraocular pressure is the leading risk factor for glaucoma. It is reported that trabecular meshwork cell injury is closely associated with the elevated intraocular pressure. The current study aimed to investigate the role of small nucleolar RNA host gene 3 (SNHG3) in human trabecular meshwork (HTM) cells under oxidative stress. A series of experiments including real-time quantitative polymerase chain reaction, subcellular fractionation assay, western blot analysis, cell counting kit-8 assay, RNA pull down, flow cytometry analysis, and RNA immunoprecipitation assay were used to explore the biological function and regulatory mechanism of SNHG3 in HTM cells under oxidative stress. First, we observed that H₂ O₂ induced SNHG3 upregulation in HTM cells. Then, we found that SNHG3 silencing alleviated H₂ O₂ -induced oxidative damage in HTM cells. Moreover, snail family transcriptional repressor 2 (SNAI2) knockdown alleviated the oxidative damage induced by H₂ O₂ in HTM cells. Mechanistically, SNHG3 bound with ELAV like RNA binding protein 2 (ELAVL2) to stabilize SNAI2. Finally, SNAI2 overexpression counteracted the effect of SNHG3 silencing on H₂ O₂ -treated HTM cells. In conclusion, our results demonstrated that SNHG3 cooperated with ELAVL2 to modulate cell apoptosis and extracellular matrix accumulation by stabilizing SNAI2 in HTM cells under oxidative stress.

Characterization of TGF-β by Induced Oxidative Stress in Human Trabecular Meshwork Cells

Oxidative stress generated by reactive oxygen species (ROS) plays a critical role in the pathomechanism of glaucoma, which is a multifactorial blinding disease that may cause irreversible damage within human trabecular meshwork cells (HTMCs). It is known that the transforming growth factor-β (TGF-β) signaling pathway is an important component of oxidative stress-induced damage related to extracellular matrix (ECM) fibrosis and activates cell antioxidative mechanisms. To elucidate the dual potential roles and regulatory mechanisms of TGF-β in effects on HTMCs, we established an in vitro oxidative model using hydrogen peroxide (H₂O₂) and further focused on TGF-β-related oxidative stress pathways and the related signal transduction. Via a series of cell functional qualitative analyses to detect related protein level alterations and cell fibrosis status, we illustrated the role of TGF-β1 and TGF-β2 in oxidative stress-induced injury by shTGF-β1 and shTGF-β2 knockdown or added recombinant human TGF-β1 protein (rhTGF-β1). The results of protein level showed that p38 MAPK, TGF-β, and its related SMAD family were activated after H₂O₂ stimulation. Cell functional assays showed that HTMCs with H₂O₂ exposure duration had a more irregular actin architecture compared to normal TM cells. Data with rhTGF-β1 (1 ng/mL) pretreatment reduced the cell apoptosis rate and amount of reactive oxygen species (ROS), while it also enhanced survival. Furthermore, TGF-β1 and TGF-β2 in terms of antioxidant signaling were related to the activation of collagen I and laminin, which are fibrosis-response proteins. Succinctly, our study demonstrated that low concentrations of TGF-β1 (1 ng/mL) preserves HTMCs from free radical-mediated injury by p-p38 MAPK level and p-AKT signaling balance, presenting a signaling transduction mechanism of TGF-β1 in HTMC oxidative stress-related therapies.

RhoA Activation Decreases Phagocytosis of Trabecular Meshwork Cells

PURPOSE

RhoA signaling is important for the regulation of intraocular pressure through the trabecular meshwork (TM). However, the relationship between RhoA signaling and phagocytosis in TM cells is unclear. The purpose of this study was to investigate the effects of RhoA signaling on the phagocytosis of TM cells.

MATERIALS AND METHODS

TM cells were isolated from enucleated porcine eyes and treated with lysophosphatidic acid (LPA) or calpeptin to activate RhoA to determine phagocytic activity. To assess phagocytic activity, TM cells were incubated with pHrodo® Red S. aureus bioparticles, and the fluorescence intensity was measured using a cell sorter. The phagocytic activity of RhoA knockdown TM cells was also assessed using small interfering RNA (siRNA). To resolve the effects of dexamethasone on phagocytosis, TM cells were treated with dexamethasone for 72 h. The immunocytochemistry of vinculin and F-actin were evaluated in LPA- and dexamethasone-treated TM cells.

RESULTS

RhoA activities after treatment with 10 µM LPA and 100 µM calpeptin were 1.38 ± 0.026-fold and 1.47 ± 0.070-fold higher, respectively, compared with the control. The phagocytic activity was reduced by LPA (0.67 ± 0.099) and calpeptin (0.57 ± 0.016), compared with the control. C3 transferase (Rho inhibitor) and Y-27632 (Rho-associated kinase inhibitor) prevented the effects of LPA on phagocytosis, and C3 partially inhibited the effects of calpeptin on phagocytosis. Knockdown of RhoA prevented the effect of LPA on phagocytosis. By immunostaining, LPA-induced stress fiber and focal adhesion formation was prevented by C3 and Y-27632 treatment. Moreover, RhoA knockdown prevented the effects of LPA on F-actin and focal adhesion. Dexamethasone treatment decreased phagocytic activity and increased stress fiber and focal adhesion. Y-27632 prevented the effects of dexamethasone on phagocytosis, and on stress fiber and focal adhesion fomation.

CONCLUSIONS

These results suggest that the RhoA signal pathway regulates the phagocytic activity of TM cells.

Abbreviations: TM: trabecular meshwork; LPA: lysophosphatidic acid; C3: C3 transferase; ROCK: Rho-associated kinase; siRNA: small interfering RNA.

Molecular Genetics and Functional Analysis Implicate CDKN2BAS1-CDKN2B Involvement in POAG Pathogenesis

The genes in the 9p21 locus (CDKN2B-AS1 & CDKN2B) are widely associated with Primary open-angle glaucoma (POAG). However, the functional importance of this locus in POAG pathogenesis is still unexplored. This study investigated the role of CDKN2BAS1-CDKN2B axis in POAG. We observed significant association of CDKN2B-AS1 SNP rs4977756 with POAG and its endophenotypic traits (vertical cup-disc ratio (p = 0.033) and central corneal thickness (p = 0.008)) by screening African American POAG cases (n = 1567) and controls (n = 1600). A luciferase reporter assay in Human embryonic kidney 293T (HEK293T) cells revealed that the region surrounding rs4977756 likely serves as a transcriptional repressor. siRNA-mediated knockdown of CDKN2B-AS1 in HEK293T cells and trabecular meshwork (TM) cells resulted in significantly increased expression of CDKN2B, which was also observed in human POAG ocular tissues. Pathway focused qRT-PCR gene expression analysis showed increased cellular senescence, TGFβ signaling and ECM deposition in TM cells after CDKN2B-AS1 suppression. In conclusion, we report that CDKN2B-AS1 may act as a regulator, and it could function by modulating the expression of CDKN2B. In addition, increase in CDKN2B levels due to CDKN2B-AS1 suppression may result in the senescence of trabecular meshwork cells leading to POAG pathogenesis.

An advanced in vitro model to assess glaucoma onset

Glaucoma is the second leading cause of blindness worldwide. Currently, glaucoma treatments aim to lower intraocular pressure by decreasing aqueous humor production or increasing aqueous humor outflow through pharmacological approaches or trabeculectomy. The lack of an effective cure requires new therapeutic strategies. We compared the bio­logical responses of a three-dimensional trabecular meshwork model with or without perfusion bioreactor technology to better understand the early molecular changes induced by prolonged oxidative stress conditions induced by repeated daily peroxide exposure. We used standard 3D cultures of trabecular meshwork cells in Matrigel cultured under either static and dynamic conditions for one week. We studied changes in F-actin expression and organization in the cells, cellular metabolic activity, proinflammatory gene expression, expression of pro- and anti-apoptotic proteins, PARP-1 cleavage, and NFκB activation in the model. We demonstrate that the dynamic conditions improve the adaptive behavior of 3D trabecular meshwork cultures to chronic oxidative stress via offsetting pathway activation.

Gap junction protein connexin43 and tunneling nanotubes in human trabecular meshwork cells

Intercellular communication via gap junctions and tunneling nanotubes (TNT) play pivotal roles for cell differentiation and proliferation and homeostasis. Intercellular communication has been found in human trabecular meshwork cells, which are key elements for allowing the direct passing aqueous humor and for maintaining the homeostasis of intraocular pressure. Here we showed the expression of gap junction protein connexin43 in human trabecular meshwork cells, and the presence of TNTs in these cells labeled with enhanced GFP generated using highly efficient lentiviral transduction. More importantly, the TNTs in human trabecular meshwork cells were significantly reduced after shRNA or CRISPR Cas9 mediated knockdown of Cx43 in these cells. The results indicated that gap junction protein connexin43 may play an important role in TNTs formation in human trabecular meshwork cells.

Targeted deletion of Cyp1b1 in pericytes results in attenuation of retinal neovascularization and trabecular meshwork dysgenesis

Mutations in cytochrome P450 1B1 (CYP1B1) gene are reported in patients with primary congenital glaucoma. Cyp1b1-deficient (Cyp1b1-/-) mice show dysgenesis of the trabecular meshwork (TM) tissue and attenuation of retinal neovascularization during oxygen-induced ischemic retinopathy (OIR). Although retinal vascular cells, including endothelial cells (EC), pericytes (PC), astrocytes (AC), and TM endothelial cells express CYP1B1, the cell autonomous contribution of CYP1B1 to attenuation of retinal neovascularization and TM tissue dysgenesis remains unknown. Here we determined the impact lack of CYP1B1 expression in EC, PC or AC has on retinal neovascularization and TM tissue integrity. We generated Cyp1b1-transgenic mice with vascular cell-specific targeted Cre⁺-deletion in EC (Cyp1b1 ^EC), in PC (Cyp1b1 ^PC) and in AC (Cyp1b1 ^AC). Pathologic retinal neovascularization during OIR was evaluated by collagen IV staining of retinal wholemounts. Structural morphology of TM tissue was examined by transmission electron microscopy (TEM). The assessment of retinal neovascularization indicated a significant decrease in retinal neovascular tufts only in Cyp1b1 ^PC mice compared with control mice. TEM evaluation demonstrated Cyp1b1 ^PC mice also exhibited a defect in TM tissue morphology and integrity similar to that reported in Cyp1b1-/- mice. Thus, Cyp1b1 expression in PC plays a significant role in retinal neovascularization and the integrity of TM tissue.

Effect of Myricetin on Primary Open-angle Glaucoma

Background

Primary open angle glaucoma (POAG) is the most common form of glaucoma, with a multifactorial etiology that results in retinal ganglion cell death and loss of vision. In this study, we assessed the effects of myricetin on the trabecular meshwork cells in POAG.

Methods

In the in-vivo model, glaucoma was induced in Sprague-Dawley rats by injecting hyaluronic acid into the anterior chamber of the eye (every week for six-weeks). Treatment group rats were administered myricetin (25, 50 or 100 mg/ kg body weight via oral gavage) each day for of six weeks.

Results

POAG TM cells exposed to myricetin (25, 50 or 100 μM) exhibited significantly lowered reactive oxidative species (ROS) levels and lipid peroxidation products. The expressions of transforming growth factors (TGFβ1/β2), vascular endothelial growth factor, and senescence markers (senescence associated-β-galactosidase, cyclin-dependent kinase inhibitors-p16 and p21) were substantially down-regulated in POAG TM cells exposed to myricetin. Myricetin effectively prevented IOP elevation in glaucoma-induced rats and decreased inflammatory cytokines (IL-1α, IL-1β, IL-6, Il-8, TNF-α) in the aqueous humor and POAG TM cells of glaucoma-induced rats.

Conclusion

The observations of the study illustrate the protective effects of myricetin in glaucomatous TM cells.

Homocysteine induces oxidative stress to damage trabecular meshwork cells

The aim of the present study was to investigate the effect of homocysteine (Hcy) in on human trabecular meshwork cells (HTMCs). A total of 41 patients with primary open-angle glaucoma (POAG) and 53 patients with senile cataracts (control group) were recruited. Plasma and aqueous humor samples were collected and the Hcy concentrations were determined using enzymatic cycling assays. In cell experiments, normal HTMCs were passaged and randomly divided into a blank control group, a normal HTMC group and experimental groups, which were treated with different concentrations of Hcy. The HTMC activities were detected using the Cell Counting Kit-8 method and the HTMC mitochondrial membrane potential (MMP) was detected using JC-1 staining. Reactive oxygen species (ROS) released by trabecular meshwork cells was detected using flow cytometry and superoxide dismjutase-1 (SOD1) expression was detected using immunoblotting. The results revealed that the concentration of Hcy in the plasma and aqueous humor of the POAG group (14.44±0.86 and 1.60±0.27 µmol/l, respectively) was significantly higher compared with the control group (10.82±0.29 and 0.69±0.39 µmol/l). All tested concentrations (30, 100, 300 and 1,000 µmol/l) of Hcy reduced the MMP in HTMCs and inhibited HTMC proliferation in a dose-dependent manner. ROS production by HTMCs significantly increased with increased concentrations of Hcy, whereas SOD1 expression significantly decreased in a dose-dependent manner. In summary, patients with POAG were demonstrated to have increased concentrations of Hcy in the plasma and aqueous humor. High concentrations of Hcy in HTMCs induced an oxidative stress state, thereby further inhibiting HTMC proliferation. The results of the present study demonstrate that Hcy may be a potential treatment target in patients with POAG.

Pentablock copolymer dexamethasone nanoformulations elevate MYOC: in vitro liberation, activity and safety in human trabecular meshwork cells

AIM

The aim of this study is to examine the elevation of MYOC in long-term treatment of human trabecular meshwork (HTM) cells using dexamethasone (DEX) encapsulated pentablock (PB) copolymer-based nanoparticles (NPs) (DEX-PB-NPs).

MATERIALS & METHODS

PB copolymers and DEX-PB-NPs were synthesized and characterized using nuclear magnetic resonance, gel permeation chromatography, and X-ray diffraction analyses. MYOC levels secreted from HTM cells were measured by western blot (WB) analysis.

RESULTS

DEX-PB-NPs were formulated in the size range of 109 ± 3.77 nm (n = 3). A long term DEX release from the NPs was observed over three months. Cell viability and cytotoxicity were not affected up to 12 weeks of treatment with PB-copolymer or DEX-PB-NPs. WB data from five HTM cell strains showed that MYOC levels increased by 5.2 ± 1.3, 7.4 ± 4.3, and 2.8 ± 1.1-fold in the presence of DEX-PB-NPs compared with 9.2 ± 3.8, 2.2 ± 0.5, and 1.5 ± 0.3-fold at 4, 8 and 12 weeks in control-DEX treatment group, respectively (n = 5). Based on the decline in MYOC levels after withdrawal of DEX from control wells, DEX-PB-NPs released the DEX for at least 10 weeks.

CONCLUSION

The treatment of HTM cells using DEX-PB-NPs were analyzed in this study. The in vitro cell-based system developed here is a valuable tool for determining the safety and effects of steroids released from polymeric NPs.

Expression of 14-3-3 Zeta Protein in Dexamethasone-Treated Mice and Human TM-1 Cells

PURPOSE

14-3-3 zeta protein plays a potential protective role in neurodegenerative disease. Given that glaucoma and neurodegenerative diseases share a similar pathogenesis, it is possible that 14-3-3 zeta may have a similar protective effect in the glaucomatous process. In the present study, we measured the expression of 14-3-3 zeta in vivo (mouse eyes) and in vitro in a transformed human trabecular meshwork (HTM) cell line, TM-1, and assessed the possible roles of this protein in dexamethasone (DEX)-treated eyes and HTM cells.

METHODS

Mouse eyes were randomly treated with 0.1% dexamethasone (DEX) eye drops or phosphate-buffered solution (PBS) for 28 days. The expression and distribution of 14-3-3 zeta protein in mouse eyes were examined using immunofluorescence. TM-1 cells were treated with DEX (10^-6 or 10^-7 M) or PBS for 1, 4, or 7 days, and the mRNA and protein expression of 14-3-3 zeta were detected by real-time RT-PCR and Western blotting.

RESULTS

14-3-3 zeta protein was highly expressed in the mouse cornea, trabecular meshwork (TM), and ciliary body. Intraocular pressure (IOP) was significantly elevated, whereas the 14-3-3 zeta expression was significantly decreased in mouse TM after 0.1% DEX treatment for 28 days. In vitro, treatment with 10^-7 M DEX mildly increased 14-3-3 zeta mRNA and protein expression (p > 0.05), whereas 10^-6 M DEX significantly decreased expression of 14-3-3 zeta mRNA and protein (p < 0.05) compared to the control (Ctrl) group at the seventh day.

CONCLUSIONS

DEX can increase IOP in mouse eyes and concurrently downregulate 14-3-3 zeta protein expression in mouse TM. The effects of DEX on 14-3-3 zeta expression in vitro were both dose- and time-related. Our results suggest that alterations in 14-3-3 zeta protein may be implicated in DEX-induced pathological elevated IOP.

Effects of transforming growth factor-β2 on myocilin expression and secretion in human primary cultured trabecular meshwork cells

High intraocular pressure (IOP) is a risk factor for primary open-angle glaucoma (POAG). The trabecular meshwork (TM), a reticular tissue in the outflow passage of the aqueous humor (AH), is a major contributor to intraocular outflow resistance. High levels of myocilin (MYOC), which is expressed in the TM, are associated with high IOP. Furthermore, transforming growth factor-β2 (TGF-β2) concentrations in human AH are significantly elevated in POAG patients. This study was designed to investigate the effects of TGF-β2 on MYOC expression and secretion in human primary cultured TM cells. Primary cultured human TM cells were treated with 0 (control group), 1, 10, and 100 ng/mL TGF-β2 for 12, 24, or 48 h. MYOC mRNA and protein expressions in TM cells and protein secretion in conditioned media were analyzed by semi-quantitative RT-PCR, Western blotting, and enzyme-linked immunosorbent assays (ELISA), respectively. TM cells treated with 1, 10, and, 100 ng/mL TGF-β2 for 48 h showed higher MYOC mRNA and protein expressions than those in the control group (0 ng/mL TGF-β2) (all P < 0.05). Treatment with TGF-β2 for 48 h also induced MYOC secretion in conditioned media in a dose-dependent manner (0 ng/mL: 7.107±1.163 pg/ml; 1 ng/mL: 7.879±1.894 pg/ml; 10 ng/mL: 8.063±1.181 pg/ml; 100 ng/mL: 8.902±0.699 pg/ml; all P < 0.05). In Conclusion, TGF-β2 induced MYOC expression and secretion in human primary cultured TM cells. Further investigations are required to confirm the involvement of these two factors in POAG pathogenesis.

Imaging the effects of prostaglandin analogues on cultured trabecular meshwork cells by coherent anti-stokes Raman scattering

PURPOSE

The aim of this study was to nondestructively monitor morphological changes to the lipid membranes of primary cultures of living human trabecular meshwork cells (hTMC) without the application of exogenous label.

METHODS

Live hTMC were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). The hTMC were treated with a commercial formulation of latanoprost (0.5 μg/mL) for 24 hours before imaging. Untreated cells and cells treated with vehicle containing the preservative benzalkonium chloride (BAK; 2 μg/mL) were imaged as controls. After CARS/TPAF imaging, hTMC were fixed, stained with the fluorescent lipid dye Nile Red, and imaged by conventional confocal microscopy to verify lipid membrane structures.

RESULTS

Analysis of CARS/TPAF images of hTMC treated with latanoprost revealed multiple intracellular lipid membranes absent from untreated or BAK-treated hTMC. Treatment of hTMC with sodium fluoride or ouabain, agents shown to cause morphological changes to hTMC, also did not induce formation of intracellular lipid membranes.

CONCLUSIONS

CARS microscopy detected changes in living hTMC morphology that were validated by subsequent histological stain. Prostaglandin-induced changes to hTMC involved rearrangement of lipid membranes within these cells. These in vitro results identify a novel biological response to a class of antiglaucoma drugs, and further experiments are needed to establish how this effect is involved in the hypotensive action of prostaglandin analogues in vivo.