Role of tissue growth factors in aqueous humor homeostasis

Occurrence of Oxidative Stress and Premature Senescence in the Anterior Segment of Acute Primary Angle-Closure Eyes

Purpose

To explore whether oxidative stress and premature senescence occur in the anterior segment of acute primary angle-closure (APAC) eyes after increased intraocular pressure.

Methods

The eye samples of 21 APAC patients, 22 age-related cataract patients, and 10 healthy donors were included. Aqueous humor (AqH), iris, and anterior lens capsule samples were collected. The levels of oxidative stress markers and senescence-associated secretory phenotype (SASP)–related cytokines in AqH were estimated using relevant reagent kits and multiplex bead immunoassay technique. The intensity of relevant markers in anterior segment tissues was examined by immunofluorescence- and senescence-associated β-galactosidase (SA-β-gal) staining.

Results

Oxidative stress marker levels elevated significantly in the AqH of APAC eyes. Reactive oxygen species (ROS) and 8-hydroxydeoxyguanosine levels were positively correlated with preoperative peak intraocular pressure and age, whereas reduced glutathione/oxidized glutathione (GSH/GSSH) ratio was negatively correlated with both parameters. The levels of several SASP-related cytokines were markedly increased. ROS and malondialdehyde levels were positively correlated with the levels of some SASP-related cytokines, whereas superoxide dismutase level and GSH/GSSH ratio showed an opposite trend. The number of cells positive for oxidative mitochondrial DNA damage and apoptosis-related markers increased in the iris and anterior lens capsule of the APAC group. Senescence-associated markers (p16, p21, and p53) and SA-β-gal activity were increased in the iris of the APAC group.

Conclusions

Oxidative stress and premature senescence occurred in the anterior segment of APAC patients, suggesting that they may be involved in the development of pathological changes in the anterior segment of APAC eyes.

Immune responses to injury and their links to eye disease

The eye is regarded as an immune privileged site. Since the presence of a vasculature would impair vision, the vasculature of the eye is located outside of the central light path. As a result, many regions of the eye evolved mechanisms to deliver immune cells to sites of dysgenesis, injury, or in response to the many age-related pathologies. While the purpose of these immune responses is reparative or protective, cytokines released by immune cells compromise visual acuity by inducing inflammation and fibrosis. The response to traumatic or pathological injury is distinct in different regions of the eye. Age-related diseases impact both the anterior and posterior segment and lead to reduced quality of life and blindness. Here we focus attention on the role that inflammation and fibrosis play in the progression of age-related pathologies of the cornea and the lens as well as in glaucoma, the formation of epiretinal membranes, and in proliferative vitreoretinopathy.

Potential effects of angiogenesis-related factors on the severity of APAC and surgical outcomes of trabeculectomy

Background

EPO (erythropoietin) and PDGF (platelet derived growth factor) families are thought to be associated with angiogenesis under hypoxic condition. The sharp rise of intraocular pressure in acute primary angle closure (APAC) results in an inefficient supply of oxygen and nutrients. We aimed to measure the expression of EPO and PDGF family members in APAC eyes and demonstrate their associations with APAC’s surgical success rate.

Methods

Concentrations of EPO, PDGF-AA, -BB, -CC and -DD collected in aqueous humor samples of 55 patients recruited were measured. Before operations, correlations between target proteins and IOP (intraocular pressure) were detected between APAC (acute primary angle closure) and cataract patients. Based on the post-operative follow-up, the effects of EPO and PDGF family members on the successful rate of trabeculectomy were tested.

Results

The levels of EPO, PDGF-CC and -DD were significantly elevated in the APAC group compared to the cataract group. During the post-operative follow-up, EPO, PDGF-CC and -DD showed significant differences between the success and failure groups. In multivariable linear regression analyses, failed filtration surgery was more likely in APAC eyes with higher EPO level. The Kaplan-Meier survival plot suggested that the success rate in eyes with low EPO level was significantly higher than that in eyes with high EPO level.

Conclusion

The levels of EPO, PDGF-CC and -DD were significantly elevated in failure group. EPO level correlated with preoperative IOP and numbers of eyedrops, and higher EPO level in aqueous humor is a risk factor for trabeculectomy failure. It can be a biomarker to estimate the severity of APAC and the success rate of surgery. The investigation of mechanism of EPO in APAC a may have potential clinical applications for the surgical treatment of APAC.

Association of High-Mobility Group Box-1 with Inflammationrelated Cytokines in the Aqueous Humor with Acute Primary Angle-Closure Eyes

AIM

The aim of this study was to measure the levels of High-mobility group box-1 (HMGB1) and inflammation-related cytokines in the aqueous humor of patients with acute primary angle-closure glaucoma (APAG) and age-related cataract eyes (ARC).

METHODS

Aqueous humor samples were obtained from 59 eyes of 59 Chinese subjects (APAG, 32 eyes; and ARC, 27eyes). The multiplex bead immunoassay technique was used to measure the levels of HMGB1 and IL-8, IL-6, G-CSF, MCP-3, VEGF, sVEGFR- 1, sVEFGR-2, TNF-α, PDGF, and IL-10 in aqueous. The data of Patients' demographics and preoperative intraocular pressure (IOP) were also collected for detailed analysis.

RESULTS

The APAG group showed significantly elevated concentrations of HMGB1, IL- 8, IL-6, G-CSF, VEGF, sVEGFR-1, and TNF-α than those in the ARC group. Aqueous HMGB1 level correlated significantly with IOP, IL-8, IL-6, G-CSF and sVEGFR-1 levels but not with age, TNF-α, or VEGF levels.

CONCLUSION

The aqueous level of HMGB1 is elevated in APAG and associated with aqueous level of inflammation-related cytokines, suggesting an association between elevated levels of HMGB1, APAC and certain inflammatory modulators which, of course, should lead to further investigations in order to demonstrate the cause and effect.

Causative glaucoma treatment: promising targets and delivery systems

Glaucoma is one of the most common causes of blindness worldwide. Elevated intraocular pressure (IOP) is the major modifiable risk factor of the disease. Conventional therapy suffers from poor compliance, low bioavailability, and the lack of causative treatment options. To improve therapeutic success, it is crucial to identify major mediators of pathological changes associated with elevated IOP and to intervene at the molecular level. Here, we discuss relevant key functions of transforming growth factor-β2 (TGF-β2), connective tissue growth factor (CTGF), integrins, Rho-associated kinase (ROCK), and nitric oxide (NO) with regard to the onset of glaucoma, highlighting new drug delivery approaches for causative treatment.

Does oral spirulina protect the cornea from formaldehyde exposure? Application to anatomy laboratories

In this study, the protective effect of spirulina on corneal injury after formaldehyde (FA) exposure was assessed. Thirty adult male albino rats were divided into four groups. Group I: 12 rats were divided into two subgroups: I-a (negative control) and I-b (positive control). Group II (spirulina group): six rats received spirulina via an oral gavage feeding needle at a daily dose of 400 mg/kg b.w. Group III (FA exposure group): six rats were subjected to 10% FA inhalation for 2 h per day for 2 weeks (5 days per week). Group IV (FA exposure group treated with spirulina): six rats were exposed to 10% FA as in group III, with co-administration of spirulina as in group II. After 2 weeks, all the rats were sacrificed; the corneas were dissected and processed for paraffin sections. The sections were stained with hematoxylin and eosin (H&E), Masson's trichrome (MTC), or avidin-biotin peroxidase, and examined by light microscopy. The sections of rat cornea exposed to FA (Group III) showed disorganized and compressed epithelium with erosions. Subepithelial mononuclear cell infiltration and invasion of blood vessels were also evident. Stromal collagen fibers were disorganized and widely separated. All these changes were ameliorated by administration of spirulina (Group IV). Corneal thickness was nearly normal in Group IV, statistically significantly less than in Group III. It was concluded that spirulina protects against FA-induced corneal injury in rats. Clin. Anat. 31:830-837, 2018. © 2018 Wiley Periodicals, Inc.

Matricellular Proteins Play a Potential Role in Acute Primary Angle Closure

PURPOSE

To quantify levels of matricellular proteins in aqueous humor samples from acute primary angle closure (APAC) and non-glaucomatous cataract eyes and investigate their correlation with intraocular pressure (IOP) fluctuation.

MATERIALS AND METHODS

Aqueous humor samples were collected from 63 eyes including 29 current APAC eyes, 12 previous APAC eyes, and 22 cataract eyes. Concentrations of four main matricellular proteins (SPARC, tenascin-C, thrombospondin-2, and osteopontin) were measured using multiplexed immunoassay kits. Correlations between matricellular proteins and age, sex, and IOP were then detected using Spearman's rank correlation coefficient.

RESULTS

The levels of SPARC, thrombospondin-2, and osteopontin were significantly elevated in the APAC group as compared to the cataract group (p < 0.001, p < 0.001, and p = 0.009, respectively). Further separation of the APAC group into current and previous APAC groups showed that only the differences of SPARC and thrombospondin-2 between the current APAC and cataract groups were significant (both p < 0.001). All four matricellular proteins were found to have a positive correlation with IOP in the current APAC group but no correlation was found in the previous APAC or cataract groups.

CONCLUSIONS

The levels of matricellular proteins were significantly elevated in the current APAC eyes and positively correlated to IOP. Further studies are necessary to investigate the molecular mechanisms and histological evidence of pathogenesis in matricellular proteins in APAC.

Diagnosis of limbal stem cell deficiency based on corneal epithelial thickness measured on anterior segment optical coherence tomography

PURPOSE

The purpose of this study is to investigate the epithelial thickness in the cornea and limbus in limbal stem cell deficiency (LSCD) using anterior segment optical coherence tomography (AS-OCT).

METHODS

This was a cross-sectional, comparative study. OCT images of 30 eyes of 19 patients with LSCD collected by AS-OCT were scanned. Corneal epithelial thickness was recorded at the central cornea and the superior, nasal, inferior, and temporal limbus. Measurment of the same region of 30 normal eyes served as control. Epithelial thickness in all locations was measured by 2 independent observers.

RESULTS

The mean epithelial layer thickness was 61.3 ± 2.9 μ in the central cornea and 62.7 ± 4.3 μ in the limbus in the control. The epithelial thickness in LSCD patients was found to be 41.33 ± 2.8 μ. An average reduction of 22.2% in the central cornea and 32.15% in the limbus was found in patients with LSCD (P < 0.05). Epithelial thinning correlated with the severity of LSCD in both cornea and limbus. In eyes with sectoral LSCD, a similar degree of epithelial thinning was also detected in the clinically unaffected limbal regions.

CONCLUSION

Both corneal and limbal epithelia become progressively thinner in LSCD. Epithelial thickness assessment using AS-OCT as a noninvasive tool could be used as a diagnostic measure of LSCD.

Link between neurodegeneration and trabecular meshwork injury in glaucomatous patients

Background

Glaucoma is classified as a neurodegenerative disease. However, the biomarkers of neurodegeneration in the aqueous humour of primary open angle glaucoma (POAG) eyes have not been quantitatively examined yet. In this study, levels of neurodegeneration-related cytokines in the aqueous humour of POAG eyes were measured and compared with those of non-glaucoma (senile cataract) control eyes.

Methods

This cross-sectional study included 24 patients (24 eyes) with POAG and 22 patients (22 eyes) with cataract. Aqueous humour samples were collected before the commencement of phacoemulsification surgery. The concentrations of brain-derived neurotrophic factor (BDNF), cathepsin D, myeloperoxidase (MPO), soluble intercellular adhesion molecule-1 (sICAM-1), soluble neural cell adhesion molecule (sNCAM), soluble vascular cell adhesion molecule-1 (sVCAM-1), and plasminogen activator inhibitor-1 (PAI-1) were measured using the Luminex suspension array technique. The clinical characteristics of the patients were also obtained for correlation analysis.

Results

Compared with the cataract group, the levels of cathepsin D (P < 0.001), sNCAM (P < 0.001) and sVCAM-1 (P = 0.007) were significantly higher in the aqueous humour samples from POAG. The levels of BDNF, sICAM-1, MPO and PAI-1 did not differ among the groups. Mean deviation (MD) values measured by the Humphrey Visual Field Analyzer were significantly associated with levels of cathepsin D (P < 0.001; ρ= − 0.668), sICAM-1 (P = 0.003; ρ= − 0.579), sVCAM-1(P < 0.001; ρ= − 0.695), and PAI-1 (P = 0.007; ρ= − 0.533). The cytokines showed a positive correlation among each other (P < 0.0083).

Conclusion

These data suggest that POAG patients had elevated levels of multiple biomarkers of neurodegeneration in the aqueous humour, and these elevated biomarkers may be related to trabecular meshwork injury.

Trial registration

This study was registered in the Chinese Clinical Trial Registry (ChiCTR-OOC-16008516) on May 22, 2016.

Pirfenidone inhibits fibrosis in foreign body reaction after glaucoma drainage device implantation

Background

The aim of this study was to investigate the antiscarring effects of pirfenidone on foreign body reaction in a rabbit model of glaucoma drainage implant surgery.

Methods

Adult New Zealand White rabbits had glaucoma drainage device implantation using Model FP8 Ahmed glaucoma valves. One eye was randomly assigned to receive postoperative intrableb injection of pirfenidone followed by topical treatment. The other eye underwent the same procedure but without the addition of pirfenidone. Histochemical staining and immunohistochemistry for blebs were performed.

Results

The degree of cellularity was smaller in the pirfenidone group than in the control group at 2 weeks post operation (P=0.005). A few foreign body giant cells were detected in the inner border of the capsule, and their numbers were similar in the control and pirfenidone groups (P>0.05). Using Masson’s trichrome stain, the inner collagen-rich layer was found to be thinner in the pirfenidone group than the control group at 4 weeks (P=0.031) and 8 weeks (P=0.022) post operation. The percentage of proliferating cell nuclear antigen-positive cells was lower in the pirfenidone group than in the control group at 2 weeks post operation (total bleb, P=0.022; inner bleb, P=0.036). Pirfenidone treatment decreased the immunoreactivity of connective tissue growth factor at 2 weeks post operation (total bleb, P=0.029; inner bleb, P=0.018). The height and area of α-smooth muscle actin expression were lower in the pirfenidone group than the control group at 2 weeks, 4 weeks, and 8 weeks post operation (all P<0.05).

Conclusion

Postoperative intrableb injection of pirfenidone followed by topical administration reduced fibrosis following glaucoma drainage device implantation. These findings suggest that pirfenidone may function as an antiscarring treatment in foreign body reaction after tube-shunt surgery.

The role of lamina cribrosa cells in optic nerve head fibrosis in glaucoma

Glaucoma is a chronic progressive optic neuropathy. There are extracellular matrix (ECM) changes associated with optic disc cupping in the optic nerve head (ONH) and subsequent visual field defects. The primary risk factor for onset and progression of glaucoma is raised intraocular pressure (IOP). Elevated IOP causes deformation at the ONH specifically at the lamina cribrosa (LC) region where there is also deposition of ECM causing the LC to initially undergo thickening and posterior migration with eventual shearing and collapse of the LC plates leading to a thin fibrotic connective tissue structure/scar. Cells that populate the LC region of the ONH are those cells that are positive for GFAP (the astrocytes) and those negative for GFAP (the LC cells). The LC cell plays an integral role in ECM remodelling producing ECM when exposed to high level mechanical stretch, TGF- β1 and a hypoxic environment.

Electrochemical behavior of surgical 316L stainless steel eye glaucoma shunt (Ex-PRESS) in artificial aqueous humor

A novel system of electrodeposited gold nanoparticles on a carbon paste electrode was utilized as an electrochemical sensor to monitor the corrosion performance of 316L stainless steel alloy in aqueous humor containing moxifloxacin hydrochloride (MFH) drug.

Mini-Review: Limbal Stem Cells Deficiency in Companion Animals: Time to Give Something Back?

Experimental animals have been used extensively in the goal of developing sight-saving therapies for humans. One example is the development of transplantation of cultured limbal epithelial stem cells (LESC) to restore vision following ocular surface injury or disease. With clinical trials of cultured LESC therapy underway in humans and a potential companion animal population suffering from similar diseases, it is perhaps time to give something back. Comparatively to humans, what is known about the healthy limbus and corneal surface physiology of companion animals is still very little. Blinding corneal diseases in animals such as symblepharon in cats with Feline Herpes Virus-1 infections require a basic understanding of the functional companion animal limbus and corneal stem cells. Our understanding of many other vision threatening conditions such as scarring of the cornea post-inflammation with lymphocytic-plasmacytic infiltrate in dogs (aka chronic superficial keratitis) or pigment proliferation with Pigmentary Keratitis of Pugs would benefit from a better understanding of the animal cornea in health and disease. This is also vital when new therapeutic approaches are considered. This review will explore the current challenges and future research directions that will be required to increase our understanding of corneal diseases in animals and consider the potential development and delivery of cultured stem cell therapy to veterinary ocular surface patients.

The Function of Matricellular Proteins in the Lamina Cribrosa and Trabecular Meshwork in Glaucoma

PURPOSE

To review the current literature regarding the role of matricellular proteins in glaucoma, specifically in the lamina cribrosa (LC) region of the optic nerve head (ONH) and the trabecular meshwork (TM).

METHODS

A literature search was performed for published articles describing the expression and function of matricellular proteins such as thrombospondin (TSP), connective tissue growth factor (CTGF), secreted protein acidic and rich in cysteine (SPARC), and periostin in glaucoma.

RESULTS

In glaucoma, there are characteristic extracellular matrix (ECM) changes associated with optic disc cupping in the ONH and subsequent visual field defects. Matricellular proteins are a family of nonstructural secreted glycoproteins, which enable cells to communicate with their surrounding ECM, including CTGF, also known as CCN2, TSPs, SPARC, periostin, osteonectin, and tenascin-C and -X, and other ECM proteins. Such proteins appear to play a role in fibrosis and increased ECM deposition. Importantly, most are widely expressed in tissues particularly in the TM and ONH, and deficiency of TSP1 and SPARC has been shown to lower intraocular pressure in mouse models of glaucoma through enhanced outflow facility.

CONCLUSION

This article highlights the role of matricellular proteins in glaucoma pathology. The potential role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC region and might therefore be potential targets for therapeutic intervention in glaucoma.

Differential nuclear expression of Yap in basal epithelial cells across the cornea and substrates of differing stiffness

Corneal epithelium is maintained throughout life by well-orchestrated proliferation of limbal epithelial stem cells, followed by migration and maturation centripetally across the ocular surface. The present study sets out to explore the role tissue stiffness (compliance) may have in directing both differentiation and centripetal migration of limbal epithelial stem cells during homeostasis. For that, we analysed the localization of the Yes-associated protein (Yap), a transcriptional co-activator previously shown to mediate cellular response and mechanical stimuli. Using both models of ocular surface compliance and normal bovine corneas we evaluated the nuclear/cytoplasmic expression ratio of Yap. Expression levels within corneal epithelial cells were compared in situ between the limbus and central cornea, and in vitro between limbal epithelial stem cells expanded upon biomimetic collagen gels of increasing stiffness. Nuclear expression of Yap was shown to increase within the expanded cells upon substrates of increasing stiffness. Subsequently, Yap was used as a novel molecular probe to investigate the mechanical microenvironment within a normal ocular surface. The in situ localization of Yap was predominantly cytoplasmic within basal limbal epithelial cells and nuclear within basal central corneal epithelial cells. Furthermore, nuclear p63 expression was not co-localized with Yap in basal limbal epithelial cells. In conclusion, the current investigation provides new insights into the relationship between Yap and distinct cell populations across the ocular surface indicating that cells experience a different mechanical environment between the limbus and central cornea. A new hypothesis is put forward, in which centripetal differences in substrate stiffness drives the migration and differentiation of limbal epithelial stem cells, thus controlling corneal epithelium homeostasis.

The role of matricellular proteins in glaucoma

Glaucoma is an optic neuropathy affecting approximately 60million people worldwide and is the second most common cause of irreversible blindness. Elevated intraocular pressure (IOP) is the main risk factor for developing glaucoma and is caused by impaired aqueous humor drainage through the trabecular meshwork (TM) and Schlemm's canal (SC). In primary open angle glaucoma (POAG), this elevation in IOP in turn leads to deformation at the optic nerve head (ONH) specifically at the lamina cribrosa (LC) region where there is also a deposition of extracellular matrix (ECM) molecules such as collagen and fibronectin. Matricellular proteins are non-structural secreted glycoproteins that help cells communicate with their surrounding ECM. This family of proteins includes connective tissue growth factor (CTGF), also known as CCN2, thrombospondins (TSPs), secreted protein acidic and rich in cysteine (SPARC), periostin, osteonectin, and Tenascin-C and -X and other ECM proteins. All members appear to play a role in fibrosis and increased ECM deposition. Most are widely expressed in tissues particularly in the TM and ONH and deficiency of TSP1 and SPARC have been shown to lower IOP in mouse models of glaucoma through enhanced outflow facility. The role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC regions and might therefore be potential targets for therapeutic intervention in glaucoma.

Notch signal regulates corneal endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EnMT) is a cell transformation process involved in both morphogenesis and pathogenesis. EnMT of corneal endothelial cells happens after endothelial injury and during ex vivo culture. Previous studies have shown that the transforming growth factor-β signaling pathway is involved in this transition. In this study, we found that rat corneal endothelial cells could spontaneously undergo EnMT during ex vivo culture. This change in rat corneal endothelial cells was associated with Notch signaling pathway activation after the first passage, which was blocked by the Notch inhibitor N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT). This inhibitor also prevented transforming growth factor β1-, β2-, and β3-induced EnMT and reversed transformed rat corneal endothelial cells to a normal phenotype. Furthermore, DAPT treatment blocked retrocorneal membrane formation in a rat corneal endothelium damage model. Our study indicates that the Notch signaling pathway is involved in the corneal EnMT process, which may be a novel therapeutic target for treating corneal endothelial fibrogenic disorders.

Shotgun proteomics reveals specific modulated protein patterns in tears of patients with primary open angle glaucoma naïve to therapy

Primary open angle glaucoma (POAG) is one of the main causes of irreversible blindness worldwide. The pathogenesis of POAG is still unclear. Alteration and sclerosis of trabecular meshwork with changes in aqueous humor molecular composition seem to play the key role. Increased intraocular pressure is widely known to be the main risk factor for the onset and progression of the disease. Unfortunately, the early diagnosis of POAG still remains the main challenge. In order to provide insight into the patho-physiology of glaucoma, here we report a shotgun proteomics approach to tears of patients with POAG naïve to therapy. Our proteomics results showed 27 differential tear proteins in POAG vs. CTRL comparison (25 up regulated proteins in the POAG group and two unique proteins in the CTRL group), 16 of which were associated with inflammatory response, free radical scavenging, cell-to-cell signaling and interaction. Overall the protein modulation shown in POAG tears proves the involvement of biochemical networks linked to inflammation. Among all regulated proteins, a sub-group of 12 up-regulated proteins in naïve POAG patients were found to be down-regulated in medically controlled POAG patients treated with prostanoid analogues (PGA), as reported in our previous work (i.e., lipocalin-1, lysozyme C, lactotransferrin, proline-rich-protein 4, prolactin-inducible protein, zinc-alpha-2-glycoprotein, polymeric immunoglobulin receptor, cystatin S, Ig kappa chain C region, Ig alpha-2 chain C region, immunoglobulin J chain, Ig alpha-1 chain C region). In summary, our findings indicate that the POAG tears protein expression is a mixture of increased inflammatory proteins that could be potential biomarkers of the disease, and their regulation may be involved in the mechanism by which PGA are able to decrease the intraocular pressure in glaucoma patients.

Suppressive effect of aqueous humor from person with type 2 diabetes with or without retinopathy on reactive oxygen species generation

AIM

To evaluate the antioxidant capacity and concentrations of vascular endothelial growth factor (VEGF) and interleukin 6 (IL-6) in aqueous humor from patients with type 2 diabetes mellitus (T2DM) with or without retinopathy.

METHODS

Aqueous humor was obtained during elective cataract surgery from T2DM patients with or without retinopathy and from healthy subjects. Reducing response was evaluated by MTT dye reduction and the generation of reactive oxygen species (ROS) was determined by chemiluminescence assay. Granulocytes were treated with phorbol dibutyrate (PDB)-stimulated. Cytokines were quantified by ELISA.

RESULTS

Antioxidant capacity of aqueous humor from patients with retinopathy was greater (P<0.05) than that of healthy controls or persons with diabetes without retinopathy. ROS production in PDB (protein kinase C activator)-stimulated granulocytes from T2DM patients with or without retinopathy was inhibited by autologous aqueous humor. Concentrations of VEGF and IL-6 were similar in aqueous humor from healthy controls and from patients without retinopathy, but lower (P<0.05) than those from T2DM patients with retinopathy. Plasma levels of VEGF and IL-6 were similar (P>0.05) in healthy controls and in T2DM patients with and without retinopathy.

CONCLUSION

Aqueous humor from T2DM patients with retinopathy exhibits elevated antioxidant activity with significant suppressive effect on ROS production and enhanced levels of locally secreted VEGF and IL-6 in comparison with T2DM patients without retinopathy. These results suggest an inflammatory profile in the absence of typical oxidative stress for T2DM patients with retinopathy, possibly resulting from the compensatory antioxidant response detected in the aqueous humor improving the ocular redox state.

Limbal epithelial cell therapy: past, present, and future

The cornea, the clear window at the front of the eye, transmits light to the retina to enable vision. The corneal surface is renewed by stem cells located at the peripheral limbal region. These cells can be destroyed by a number of factors, including chemical burns, infections, and autoimmune diseases, which result in limbal stem cell deficiency (LSCD), a condition that can lead to blindness. Established therapy for LSCD based on ex vivo expanded limbal epithelial cells is currently at a stage of refinement. Therapy for LSCD is also rapidly evolving to include alternative cell types and clinical approaches as treatment modalities. In the present perspectives chapter, strategies to treat LSCD are discussed and advances in this important field of regenerative medicine are highlighted.

Comparative study of the effects of recombinant human epidermal growth factor and basic fibroblast growth factor on corneal epithelial wound healing and neovascularization in vivo and in vitro

PURPOSE

This study was undertaken to investigate the effects of recombinant human epidermal growth factor (rhEGF) and basic fibroblast growth factor (bFGF) on corneal wound healing and neovascularization (CNV).

METHODS

The positive effects of 10 ng/ml rhEGF and bFGF on the proliferation of corneal epithelial cells (SD-HCEC1s), rabbit keratocyte cells (RKCs) and human umbilical vein endothelial cells (HUVECs) as well as the effects on the migration capacity on HUVECs were observed. An animal central corneal wound and CNV model was established in rabbits. One eye of each group was chosen randomly for topical administration of rhEGF, bFGF or normal saline, and variability in the area of corneal epithelial wound healing and CNV was observed.

RESULTS

The optimal concentration of rhEGF and bFGF for the proliferation of corneal epithelial cells was 10 ng/ml. The promotive effect of 10 ng/ml rhEGF on the proliferation of RKCs and HUVECs was less than that of 10 ng/ml bFGF. In the animal experiment, the healing rate of the corneal epithelium in the rhEGF group was better than in the other groups on day 1. On day 3, the healing rates of the 3 groups were nearly equal. The CNV area in the rhEGF group was less than that of the bFGF group.

CONCLUSIONS

rhEGF and bFGF both had promotive effects on corneal epithelial wound healing, but rhEGF had a weaker promotive effect on CNV than bFGF. With long-term application of growth factor drugs, rhEGF is suggested for lessening the growth of CNV.

Novel diabetic mouse models as tools for investigating diabetic retinopathy

OBJECTIVE

Mouse models possessing green fluorescent protein (GFP) and/or human aldose reductase (hAR) in vascular tissues have been established and crossed with naturally diabetic Akita mice to produce new diabetic mouse models.

RESEARCH DESIGN AND METHODS

Colonies of transgenic C57BL mice expressing GFP (SMAA-GFP), hAR (SMAA-hAR) or both (SMAA-GFP-hAR) in vascular tissues expressing smooth muscle actin were established and crossbred with C57BL/6-Ins2(Akita)/J (AK) mice to produce naturally diabetic offspring AK-SMAA-GFP and AK-SMAA-GFP-hAR. Aldose reductase inhibitor AL1576 (ARI) was administered in chow. Retinal and lenticular sorbitol levels were determined by HPLC. Retinal functions were evaluated by electroretinography (ERGs). Growth factor and signaling changes were determined by Western Blots using commercially available antibodies. Retinal vasculatures were isolated from the neural retina by enzymatic digestion. Flat mounts were stained with PAS-hematoxylin and analyzed.

RESULTS

Akita transgenics developed DM by 8 weeks of age with blood glucose levels higher in males than females. Sorbitol levels were higher in neural retinas of AK-SMAA-GFP-hAR compared to AK-SMAA-GFP mice. AK-SMAA-GFP-hAR mice also had higher VEGF levels and reduced ERG scotopic b-wave function, both of which were normalized by AL1576. AK-SMAA-GFP-hAR mice showed induction of the retinal growth factors bFGF, IGF-1, and TGFβ, as well as signaling changes in P-Akt, P-SAPK/JNK and P-44/42 MAPK that were also reduced by ARI treatment. Quantitative analysis of flat mounts in 18 week AK-SMAA-GFP-hAR mice revealed increased loss of nuclei/capillary length and a significant increase in the percentage of acellular capillaries present which was not seen in AK-SMAA-GFP-hAR treated with ARI.

CONCLUSIONS/SIGNIFICANCE

These new mouse models of early onset diabetes may be valuable tools for assessing both the role of hyperglycemia and AR in the development of retinal lesions associated with diabetic retinopathy.

Influence of bilateral medial collateral ligament injury on mRNA expression in distal corneal tissues of control and ovariohysterectomized rabbits

PURPOSE

Corneal tissues are reported to be impacted by physiological changes (eg, menopause), systemic autoimmune diseases, and osteoarthritic-like conditions. In this study, changes in specific mRNA levels in the cornea after a ligament injury in normal and rabbits subjected to surgical menopause were examined.

METHODS

Skeletally mature female rabbits were either sham-operated (control) or were subjected to surgical menopause (OVX). Eight weeks post-OVX, subsets of control and OVX animals were subjected to bilateral injuries to their medial collateral ligaments (MCL) of the knee, and 6 and 14 weeks postinjury, corneal tissues were harvested. Using reverse transcriptase-polymerase chain reaction, mRNA levels for several relevant molecules, including matrix molecules, growth factors, cytokines, proteinases, and hormone receptors, were assessed.

RESULTS

mRNA levels for estrogen receptor, decorin, collagens, several growth factors, and inflammatory cytokines decreased in central corneal tissue 6 weeks after distal MCL injury in control animals. The central corneal tissues of animals subjected to OVX alone also exhibited decreases in mRNA levels for a similar set of molecules. When OVX animals were further subjected to MCL injury, the mRNA levels for many of these molecules did not vary from those in the uninjured OVX group. Interestingly, mRNA levels for most molecules were still altered 14 weeks post-MCL injury in the control and OVX animals, a time when the MCL has healed.

CONCLUSIONS

Corneal tissues respond to changes resulting from OVX and/or injury. OVX combined with a ligament injury does not appear to have an additive impact on corneal mRNA levels for most of the molecules assessed.

Growth factors involved in aqueous humour-induced lens cell proliferation

Lens epithelial cell proliferation is regulated by growth factors in the aqueous humour of the eye. Although the lens fibre cell-differentiating factors are well defined, the factors in aqueous that promote lens cell proliferation are not. Mitogens present in aqueous primarily signal through the MAPK/ERK and PI3-K/Akt pathways. By characterising the signalling pathways involved in lens cell proliferation, we aim to identify the factors in aqueous that regulate this process in vivo. Using rat lens epithelial explants, 5'-2'-bromo-deoxyuridine and H(3)-thymidine incorporation were used to compare the effects of aqueous, insulin-like growth factor (IGF-1), platelet-derived growth factor (PDGF-A), epidermal growth factor (EGF) and fibroblast growth factor (FGF-2) on lens cell proliferation. Western blotting was employed to characterise ERK1/2 and Akt signalling induced by these mitogens. The above assays were also repeated in the presence of selective receptor inhibitors. Similar to aqueous, FGF induced a sustained ERK1/2 signalling profile (up to 6 h), unlike IGF, PDGF and EGF that induced a transient activation of ERK1/2. In the presence of a FGF receptor (FGFR) inhibitor, the sustained aqueous-induced ERK1/2 signalling profile was perturbed, resembling the transient IGF-, PDGF- or EGF-induced profile. In the presence of other growth factor receptor inhibitors, aqueous maintained its sustained, 6 h, ERK1/2 signalling profile, although ERK1/2 phosphorylation at earlier time periods was reduced. No one-specific receptor inhibitor could block aqueous-induced lens cell proliferation; however, combinations of inhibitors could, providing FGFR signalling was blocked. Multiple growth factors are likely to regulate lens cell proliferation in vivo, with a key role for FGF in aqueous-induced signalling and lens cell proliferation.

Aqueous humour- and growth factor-induced lens cell proliferation is dependent on MAPK/ERK1/2 and Akt/PI3-K signalling

The aqueous humour of the eye is a rich source of growth factors, many of which have been shown to be lens cell mitogens; however, the identity of the endogenous mitogen(s) for lens cells is still unknown. As a first approach to identify the mechanisms by which these aqueous humour-derived growth factors induce lens cell proliferation, the present study set out to examine MAPK/ERK1/2 and PI3-K/Akt signalling associated with lens cell proliferation. Using a lens explant system, we examined the effects of different lens mitogens (aqueous humour, FGF, PDGF, IGF and EGF) using 5'-2'-bromo-deoxyuridine incorporation. In addition, we adopted immunolabelling techniques to compare the roles that the ERK1/2 and PI3-K signalling pathways play in regulating lens cell proliferation. We showed that the aqueous humour, and all the other growth factors examined, could activate ERK1/2 and PI3-K/Akt signalling. By targeting these pathways using specific pharmacological inhibitors, we were able to show that both ERK1/2 and PI3-K signalling are required for growth factor-induced lens cell proliferation, and that there was a strong correlation between the spatial distribution of proliferating cells in lens explants with ERK1/2 labelling. Furthermore, our blocking studies confirmed that PI3-K/Akt signalling can act upstream of ERK1/2, potentiating ERK1/2 phosphorylation in growth factor-induced lens cell proliferation. A better understanding of the signalling pathways required for aqueous humour-induced lens cell proliferation may ultimately allow us to identify the mitogen(s) that are important for regulating lens cell proliferation in situ.

Collagen XVIII/endostatin shows a ubiquitous distribution in human ocular tissues and endostatin-containing fragments accumulate in ocular fluid samples

BACKGROUND

The endostatin domain of type XVIII collagen (ColXVIII) inhibits neovascularization and regulates cell migration and matrix turnover. This study was designed to demonstrate the protein and gene expression patterns of ColXVIII/endostatin in the human eye and to ascertain whether endostatin is detectable in ocular fluid samples.

METHODS

Twenty human eyes enucleated on account of choroidal melanoma were used for immunohistochemical stainings with antibodies against ColXVIII and endostatin. In situ hybridization was used to localize cells responsible for the production of mRNA for ColXVIII. Tear fluid, aqueous humor, and vitreous gel samples were used for Western immunoblotting to detect endostatin fragments in these samples.

RESULTS

ColXVIII was immunolocalized to almost all ocular structures, namely the basement membranes (BMs) of the corneal and conjunctival epithelia, Descement's membrane, the anterior border layer and posterior pigmented epithelium of the iris, the BMs of the pigmented and non-pigmented ciliary epithelia, the internal wall of Schlemm's canal and trabeculae, the ciliary and iris muscle cells, the BMs of the pigment epithelium of the retina, and the internal limiting membrane. Universal expression was seen in the BMs of vascular endothelial cells, and in fibroblasts located in the conjunctiva, the iris, and the ciliary body. Endostatin showed a corresponding pattern, but additional immunostaining was present in the corneal and conjunctival epithelial cells. Most epithelial and mesenchymal cells expressed the mRNA for ColXVIII. Endostatin-containing fragments varying in size were detected in tear fluid, aqueous humor and vitreous gel samples.

CONCLUSIONS

Practically all structures of the human eye contain ColXVIII/endostatin, emphasizing its possible important structural and functional role in the human eye. Furthermore, ocular fluid samples contain endostatin fragments, which may contribute to the antiangiogenic properties of the eye.

Regulation of heavy subunit chain of gamma-glutamylcysteine synthetase by tumor necrosis factor-alpha in lens epithelial cells: role of LEDGF/p75

TNF-alpha induces oxidative stress by generating reactive oxygen species (ROS). This molecule elevates the expression of gamma-glutamylcysteine synthetase heavy subunit (gamma-GCS-HS). Lens epithelium-derived growth factor (LEDGF)/p75, a transcriptional protein, is inducible by oxidative stress and protects cells from various stresses by upregulating stress-responsive genes. This paper presents evidence that TNF-alpha elevates the expression of LEDGF and that LEDGF is one of the transactivators of gamma-GCS-HS gene. An analysis of the gamma-GCS-HS promoter sequence (-819 to +518 nt) revealed the presence of putative sites for LEDGF binding. Gel mobility assay confirmed the binding of LEDGF to the heat shock element (nGAAn) and the stress response element (A/TGGGGA/T) present in gamma-GCS-HS promoter. Transactivation experiments showed activation of gamma-GCS-HS promoter in cells overexpressing LEDGF or treated with a sublethal dose of TNF-alpha (20 ng/ml). Downregulation of gamma-GCS-HS promoter activity in cells transfected with LEDGF small interfering RNA validated the finding. Notably, cells treated with TNF-alpha (20 ng/ml) for 24 h had an increased abundance of LEDGF and gamma-GCS-HS mRNA and protein. In contrast, cells treated with TNF-alpha for longer periods or with higher concentrations of TNF-alpha showed reduced expression of LEDGF and gamma-GCS-HS and increased cellular death with higher ROS levels. Cells overexpressing LEDGF revealed elevated GSH levels (10-15%), a condition that may potentially eliminate the insult to cells induced by TNF-alpha. Thus TNF-alpha regulation of LEDGF may be physiologically important, as elevated expression of LEDGF increases the expression of endogenous gamma-GCS-HS gene, the catalytic subunit of the regulating enzyme in GSH biosynthesis that may constitute a protective mechanism in limiting oxidative stress induced by inflammatory cytokines.

Translocation of Nuclear Factor-κB on Corneal Epithelial Cells Induced by Ultraviolet B Irradiation

PURPOSE

This study was performed to elucidate the role of nuclear factor-kappaB (NF-kappaB) in the death of corneal epithelial cells after ultraviolet (UV) irradiation.

METHODS

Simian virus 40-transfected human corneal epithelial cells (T-HCECs) were used in this study. Cell cultures were irradiated with a UVB (312 nm) source located 10 cm from the bottom of the slides for 10, 20, 30, or 40 s. Cytotoxicity was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Translocation of NF-kappaB was examined by immunocytochemistry using anti-NF-kappaB p65 antibody and electrophoretic mobility shift assay (EMSA). Sulfasalazine and SN-50, specific NF-kappaB inhibitors, were used to confirm the role of NF-kappaB by pretreating samples for 30 min before UV irradiation, after which cytotoxicity and NF-kappaB translocation were evaluated.

RESULTS

When T-HCECs were irradiated with UVB, translocation of NF-kappaB was observed with immunocytochemistry. These translocations peaked 2 h after UV irradiation during EMSA. When pretreated with sulfasalazine or SN-50, the translocation of NF-kappaB was blocked. Cellular death after UV irradiation was also markedly blocked by sulfasalazine.

CONCLUSION

These findings suggest that NF-kappaB plays an important role in cellular death after UV irradiation.

Elevated aqueous humour tissue inhibitor of matrix metalloproteinase-1 and connective tissue growth factor in pseudoexfoliation syndrome

BACKGROUND/AIMS

Pseudoexfoliation syndrome (PXF) was recently found to be associated with increased expression of transforming growth factor beta(1) (TGFbeta(1)) in the aqueous humour. As concern has been raised regarding anti-TGFbeta therapy, which can potentially disrupt the maintenance of anterior chamber associated immune deviation, the authors explored the levels of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), matrix metalloproteinase-9 (MMP-9), and connective tissue growth factor (CTGF) in aqueous humour to determine if these may represent alternative therapeutic targets.

METHODS

Aqueous humour samples were collected from patients who underwent routine cataract surgery. All patients were categorised into three main groups-PXF, uveitis, and control. The PXF group was further subcategorised into three grades based on the density of the exfoliative material observed on biomicroscopy, as well as the presence or absence of glaucoma. TIMP-1, MMP-9, and CTGF levels were measured using specific enzyme immunoassays (ELISA).

RESULTS

Eyes with PXF had significantly higher aqueous humour TIMP-1 concentration (n = 56, mean (SE), 9.76 (1.10) ng/ml) compared with controls (n = 112, 5.73 (0.43) ng/ml, p<0.01). Similarly, the CTGF level in PXF eyes (n = 36, 4.38 (0.65) ng/ml) was higher than controls (n = 29, 2.35 (0.46) ng/ml, p<0.05). Further, the CTGF concentration in the PXF glaucoma group is significantly higher compared with PXF eyes without glaucoma (6.03 (1.09) ng/ml v 2.73 (0.45) ng/ml, p<0.01). The MMP-9 levels were low and below detection limit in all PXF and control samples with no statistical difference between groups.

CONCLUSION

A raised TIMP-1 level and a low MMP-9 level in aqueous humour of PXF eyes may imply a downregulation in proteolytic activity. The increased CTGF concentration supports the proposed fibrotic pathology of PXF. Regulation of MMP/TIMP expression and anti-CTGF therapy may offer potential therapeutic avenues for controlling PXF associated ocular morbidity.

Advances in glaucoma therapeutics

Glaucoma is a major cause of irreversible blindness in the world. The prevalence of glaucomatous loss in vision will continue to grow as our populations age. Ocular hypertension is a major risk factor for the development of glaucoma and current glaucoma therapy is directed at lowering intraocular pressure. Several new ocular hypotensive agents have been introduced in the past several years providing a variety of treatment options. In addition, various classes of neuroprotective agents demonstrating activity in a wide variety of animal models have been proposed as potential new glaucoma therapeutics. Although these approaches will slow the progression of vision loss, they do not directly intervene in the disease process(es). Advances have been made attempting to understand the pathogenic pathways involved in glaucomatous damage to the eye and in methods to clinically measure glaucoma damage. An increased understanding of the pathophysiology of glaucoma will lead to the development of new therapeutic agents that intervene and perhaps even reverse glaucomatous damage to the eye. There also is a need to develop new methods to clinically measure glaucoma damage because, currently, considerable damage occurs before glaucoma is diagnosed and glaucoma remains underdiagnosed in the general population.

Growth factors in the anterior segment: role in tissue maintenance, wound healing and ocular pathology

A number of growth factors and their associated receptors, including epidermal growth factor, transforming growth factor-beta, keratinocyte growth factor, hepatocyte growth factor, fibroblast growth factor and platelet-derived growth factor have been detected in the anterior segment of the eye. On binding to cellular receptors, these factors activate signalling cascades, which regulate functions including mitosis, differentiation, motility and apoptosis. Production of growth factors by corneal cells and their presence in the tear fluid and aqueous humour is essential for maintenance and renewal of normal tissue in the anterior eye and the prevention of undesirable immune or angiogenic reactions. Growth factors also play a vital role in corneal wound healing, mediating the proliferation of epithelial and stromal tissue and affecting the remodelling of the extracellular matrix (ECM). These functions depend on a complex interplay between growth factors of different types, the ECM, and regulatory mechanisms of the affected cells. Imbalances may lead to deficient wound healing and various ocular pathologies, including edema, neovascularization and glaucoma. Growth factors may be targeted in therapeutic ophthalmic applications, through exogenous application or selective inhibition, and may be used to elicit specific cellular responses to ophthalmic materials. A thorough understanding of the mechanism and function of growth factors and their actions in the complex environment of the anterior eye is required for these purposes. Growth factors, their function and mechanisms of action as well as the interplay between different growth factors based on recent in vitro and in vivo studies are presented.

Molecular imaging of the transcription factor NF-kappaB, a primary regulator of stress response

A wide range of environmental stress and human disorders involves inappropriate regulation of NF-kappaB, including cancers and numerous inflammatory conditions. We have developed transgenic mice that express luciferase under the control of NF-kappaB, enabling real-time non-invasive imaging of NF-kappaB activity in intact animals. We show that, in the absence of stimulation, strong, intrinsic luminescence is evident in lymph nodes in the neck region, thymus, and Peyer's patches. Treating mice with stressors, such as TNF-alpha, IL-1alpha, or lipopolysaccharide (LPS) increases the luminescence in a tissue-specific manner, with the strongest activity observable in the skin, lungs, spleen, Peyer's patches, and the wall of the small intestine. Liver, kidney, heart, muscle, and adipose tissue exhibit less intense activities. Exposure of the skin to a low dose of UV-B radiation increases luminescence in the exposed areas. In ocular experiments, LPS- and TNF-alpha injected NF-kappaB-luciferase transgenic mice exhibit a 20-40-fold increase in lens NF-kappaB activity, similar to other LPS- and TNF-alpha-responsive organs. Peak NF-kappaB activity occurs 6h after injection of TNF-alpha and 12h after injection of LPS. Peak activities occur, respectively, 3 and 6h later than that in other tissues. Mice exposed to 360J/m(2) of UV-B exhibit a 16-fold increase in NF-kappaB activity 6h after exposure, characteristically similar to TNF-alpha-exposed mice. Thus, in NF-kappaB-luciferase transgenic mice, NF-kappaB activity also occurs in lens epithelial tissue and is activated when the intact mouse is exposed to classical stressors. Furthermore, as revealed by real-time non-invasive imaging, induction of chronic inflammation resembling rheumatoid arthritis produces strong NF-kappaB activity in the affected joints. Finally, we have used the model to demonstrate NF-kappaB regulation by manipulating the Vitamin A status in mice. NF-kappaB activity is elevated in mice fed a Vitamin A deficient (VAD) diet, and suppressed by surplus doses of retinoic acid (RA). We thus demonstrate the development and use of a versatile model for monitoring NF-kappaB activation both in tissue homogenates and in intact animals after the use of classical activators, during disease progression and after dietary intervention.