Evaluation of ocular surface inflammation in the presence of dry eye and allergic conjunctival disease

Gene expression signatures in conjunctival fornix aspirates of patients with dry eye disease associated with Meibomian gland dysfunction. A proof-of-concept study

BACKGROUND

Meibomian gland dysfunction (MGD) is one of the most common conditions in ophthalmic practice and the most frequent cause of evaporative dry eye disease (DED). However, the immune mechanisms leading to this pathology are not fully understood and the diagnostic tests available are limited. Here, we used the nCounter technology to analyze immune gene expression in DED-MGD that can be used for developing diagnostic signatures for DED.

METHODS

Conjunctival cell samples were obtained by aspiration from patients with DED-MGD (n = 27) and asymptomatic controls (n = 22). RNA was purified, converted to cDNA, preamplified and analyzed using the Gene Expression Human Immune V2 panel (NanoString), which includes 579 target and 15 housekeeping genes. A machine learning (ML) algorithm was applied to design a signature associated with DED-MGD.

RESULTS

Forty-five immune genes were found upregulated in DED-MGD vs. controls, involved in eight signaling pathways, IFN I/II, MHC class I/II, immunometabolism, B cell receptor, T Cell receptor, and T helper-17 (Th-17) differentiation. Additionally, statistically significant correlations were found between 31 genes and clinical characteristics of the disease such as lid margin or tear osmolarity (Pearson's r < 0.05). ML analysis using a recursive feature elimination (RFE) algorithm selected a 4-gene mRNA signature that discriminated DED-MGD from control samples with an area under the ROC curve (AUC ROC) of 0.86 and an accuracy of 77.5%.

CONCLUSIONS

Multiplexed mRNA analysis of conjunctival cells can be used to analyze immune gene expression patterns in patients with DED-MGD and to generate diagnostic signatures.

Establishment of an LC-MS/MS method for quantification of lifitegrast in rabbit plasma and ocular tissues and its application to pharmacokinetic study

Lifitegrast, a lymphocyte function-associated antigen 1 antagonist, was approved by the FDA for the treatment of dry eye disease. Cornea and conjunctiva have been reported to be the sites of action of lifitegrast. To investigate the pharmacokinetics of lifitegrast, a sensitive analytical method for the determination of lifitegrast in various biological matrices such as plasma and ocular tissues is required. However, only limited information about the analytical method for lifitegrast in biological samples is available. In the present study, we aimed to develop a new liquid chromatography-tandem mass spectrometry method for the determination of lifitegrast in rabbit plasma, cornea, conjunctiva, and sclera. Lifitegrast-d6 was used as an internal standard (IS). To prepare the biological samples, protein precipitation using acetonitrile was utilized. Analytes were separated from endogenous interferences on an Atlantis dC18 (5 µm, 2.1 × 150 mm), and a mixture of 0.1 % formic acid and acetonitrile was used as the mobile phase. The mass transition of precursor to product ion was monitored at 615.2 → 145.0 for lifitegrast and 621.2 → 145.1 for IS. The calibration curves were linear over the concentration range from 2 to 500 ng/mL for plasma and 5 to 500 ng/mL in ocular tissue homogenates. Intra- and inter-day accuracy ranged from 95.76 to 106.80 % in the plasma and 94.42 to 112.80 % in the ocular tissues. Precision was within 8.56 % in the plasma and 9.72 % in the ocular tissues. The short-term, long-term, auto-sampler, and freeze-thaw stabilities of lifitegrast were validated. The developed method was applied to a pharmacokinetic study of lifitegrast in rabbits. Following ophthalmic administration, only 3.26 % of administered lifitegrast was absorbed into the systemic circulation. Peak tissue concentrations were observed at 0.5 h after dosing, and topically administered lifitegrast was mainly distributed in the cornea and conjunctiva. The finding of this study is expected to be used in further pharmacokinetic studies and formulation development.

Metabolomics approach to biomarkers of dry eye disease using 1H-NMR in rats

Dry eye disease (DED) is a chronic and progressive lesion on the ocular surface and induces symptoms, such as burning sensation, itchy eyes, heavy eyes, tired eyes, dry feeling, facial flushing, and blurred vision. The present study was performed to develop DED biomarkers using metabolomics in a rat model. DED was induced by injecting scopolamine and exposing rats to a dry condition. Scopolamine (12 mg/kg/day for 7 days) was subcutaneously injected to male Sprague-Dawley rats. The rats were placed in dry condition with air-flow and dehumidifier. Tear volume and tear breakup time (TBUT) were measured, and eyes were examined through fluorescein staining to assess DED. Mucosal damage and immune reactions were also determined. Plasma and urinary endogenous metabolites were determined using ¹H-NMR analysis. Compared with control tear and TBUT levels were significantly decreased in the DED group whereas corneal damage was significantly increased. The levels of interleukins (IL-6) and IL-1β significantly elevated in the cornea and lacrimal glands in the DED group. TNF-α was numerically increased but not significantly different between groups. Pattern recognition using principal component analysis (PCA) and orthogonal projections to latent structure-discriminant analysis (OPLS-DA) of the NMR spectra in global profiling revealed different clusters between DED and control groups. Target profiling demonstrated that PCA and OPLS-DA score plots were separated between DED and controls in plasma and urine. Subsequently, 9 plasma metabolites were selected to examine different clustering between groups, and 26 urinary metabolites were also selected. Plasma metabolites showed a non-significant rising tendency in the DED group. Urinary phenylalanine, phenylacetate, pantothenate, glycine, succinate, methanol, valine, propylene glycol, histidine, threonine, lactate, and acetate were significantly different between control and DED rats. These results may contribute to understanding the metabolic regulation that is involved in DED and might be useful for potential biomarkers related to DED in rats.

Intense Pulsed Light Treatment for Itch Associated with Allergic Keratoconjunctivitis: A Retrospective Study of 35 Cases

Objective: To conduct a preliminary assessment of intense pulsed light (IPL) treatment for allergic keratoconjunctivitis (AKC)-associated ocular itch. Background: Current control measures for AKC rely primarily on drugs. IPL is effective for dry eye disease (DED). Furthermore, phototherapy is effective for managing skin inflammation and pruritus, suggesting that eye itching could decrease in some patients having AKC complicated with DED following IPL treatment to control dry eye symptoms. Methods: Thirty-five patients having DED complicated with mid-to-severe AKC were administered three IPL treatments to the periorbital skin. The eye scores of subjective symptoms and signs of AKC and tear film breakup time (TBUT) were retrospectively assessed before and after each treatment. Results: The scores for AKC-related symptoms and signs were determined four times: on Day 1 (time 0), Day 15 (time 1), Day 45 (time 2), and Day 75 (time 3) before each treatment. The average symptom score significantly decreased with treatments (time 0: 30.97, time 1: 15.03, time 3: 10). The average sign score for both eyes decreased after the first IPL treatment (left eye: 7.97 vs. 11.38; right eye: 8.1 vs. 11.1). There were no further improvements in the signs after the last treatment. The TBUT value in the right eye increased from times 0 to 3 (2.31 vs. 4.66 vs. 7.71 vs. 7.74). The TBUT value in the left eye increased from times 0 to 3 (2.50 vs. 6.97 vs. 7.57 vs. 8.24). Conclusions: Symptoms and signs improved after IPL treatment in patients with AKC. Eye itching was gradually controlled and rarely recurred. IPL may be effective for AKC treatment.

Rebamipide ophthalmic solution modulates the ratio of T helper cell 17/regulatory T cells in dry eye disease mice

The aim of the present study was to confirm the effect of 2% rebamipide ophthalmic solution on a scopolamine‑induced dry eye (DE) mouse model, and to investigate its effect on the ratio of T helper cell 17 (Th17)/regulatory T cell (Treg) numbers. C57BL/6 mice received subcutaneous injections of scopolamine and were exposed to a low‑humidity environment in order to establish a DE model. Rebamipide eye drops (2%) administered four times daily for 2 weeks, significantly reduced the corneal staining scores and increased the tear film breakup time and tear production in the DE mice. Pathologically, the rebamipide restored the histological changes induced by DE in the cornea, conjunctiva and lacrimal gland. At a molecular level, it downregulated pro‑inflammatory and upregulated anti‑inflammatory cytokines in the conjunctiva and lacrimal gland. Furthermore, the increased Th17 and Treg levels were restored following treatment with rebamipide. In conclusion, the anti‑inflammatory and Th17/Treg balance‑preserving effects of rebamipide may contribute to the treatment of DE in mice.

Comparison of 0.1%, 0.18%, and 0.3% Hyaluronic Acid Eye Drops in the Treatment of Experimental Dry Eye

PURPOSE

To compare the efficacy of 0.1%, 0.18%, and 0.3% hyaluronic acid (HA) artificial tear in the treatment of experimental dry eye (EDE).

METHODS

EDE was established in female C57BL/6 mice through an air draft and subcutaneous scopolamine injection. The mice were divided into 5 groups according to topical treatment regimens (n = 5 each): EDE control, balanced salt solution (BSS), preservative-free 0.1% HA, 0.18% HA, and 0.3% HA. The tear film break-up time (TBUT) and corneal fluorescein staining scores were measured 5, 10, 14, 21, and 28 days after treatment. The corneal smoothness scores were measured. In addition, periodic acid-Schiff (PAS) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining were performed.

RESULTS

The values for TBUT and corneal fluorescein staining showed greater improvements in all the HA groups (P < 0.05) than in the EDE and BSS groups after 10 days of treatment. Mice treated with 0.3% HA showed a more significant improvement in all clinical parameters than did those in the EDE control, BSS, 0.1% HA, and 0.18% HA groups (all P < 0.05) after 28 days of treatment. The goblet cell counts were higher in the 0.3% and 0.18% HA groups than in the 0.1% HA group. The number of TUNEL-positive cells was the lowest in the 0.3% HA group.

CONCLUSIONS

In EDE, 0.3% HA artificial tears are more effective than the 0.1% and 0.18% HA in improving tear film instability and ocular surface staining and irregularity, in increasing the number of conjunctival goblet cells, and in decreasing corneal epithelial apoptosis.

Ocular Distribution and Pharmacokinetics of Lifitegrast in Pigmented Rabbits and Mass Balance in Beagle Dogs

PURPOSE

Lifitegrast is approved in the United States for the treatment of dry eye disease (DED). We assessed lifitegrast's ocular distribution/pharmacokinetic profile in rabbits, and ¹⁴C-lifitegrast mass balance/excretion in dogs.

METHODS

Female pigmented rabbits received a single topical ocular dose of lifitegrast (Formulation No. 1, n = 25; No. 2, n = 25) per eye twice daily (target, 1.75 mg/eye/dose). Blood/ocular tissues were collected on day 5. Beagle dogs received single intravenous (n = 10; target, 3 mg, 262 μCi/animal) and ocular (n = 8, target, 3 mg, 30 μCi/eye) doses of ¹⁴C-lifitegrast (∼8 weeks between doses). Blood, excreta, and cage rinse/wipes were collected. Concentrations were measured by mass spectrometry/liquid scintillation counting. Pharmacokinetic analyses (noncompartmental) included maximum concentration (C_max), time to C_max (t_max), and area under the concentration-time curve from 0 to 8 h (AUC_0-8).

RESULTS

In rabbits, lifitegrast C_max and AUC_0-8 were similar between formulations. C_max was highest in ocular anterior segment tissues: 5,190-14,200 ng/g [conjunctiva (palpebral/bulbar), cornea, anterior sclera]. Posterior segment tissues had lower concentrations (0-826 ng/g). AUC_0-8 followed a similar trend. Plasma concentrations were low (C_max <18 ng/mL). Tissue/plasma t_max was ∼0.25-1 h. In dogs, after intravenous/ocular doses, ¹⁴C-lifitegrast was eliminated primarily through feces. Excreted radioactivity was mainly unchanged lifitegrast.

CONCLUSIONS

High exposure of lifitegrast in rabbit ocular anterior segment tissues and low exposure in posterior segment tissues/plasma suggests that lifitegrast reaches target tissues for DED treatment, with low potential for off-target systemic/ocular effects. Excretion of unchanged ¹⁴C-lifitegrast suggests minimal drug metabolism in vivo. This is consistent with lifitegrast clinical trial efficacy/safety data.

The Conjunctiva-Associated Lymphoid Tissue in Chronic Ocular Surface Diseases

Ocular surface diseases (OSDs) represent a widely investigated field of research given their growing incidence and the negative impact on quality of life. During OSDs, cytokines generated by damaged epithelia trigger and deregulate the lymphoid cells composing the eye-associated lymphoid tissues, inducing an immune-mediated chronic inflammation that amplifies and propagates the disease during time. The conjunctiva-associated lymphoid tissue (CALT), given its particular position that permits immune cells covering the cornea, might play a crucial role in the development of OSDs. Despite the recognized inflammatory role of mucosa-associated lymphoid tissues in other stations taking contact with the external environment (gut or bronchus), CALT did not gain the deserved consideration. In the last years, the diffusion of the in vivo confocal microscopy (IVCM) stimulated the interest to CALT, especially in dry eye, ocular allergy, and glaucoma. Though the initial stimuli were different, IVCM documented similar changes, represented by increased lymphoid cells within the diffuse layer, follicles and interfollicular spaces. These findings, which need to be validated by immunohistology, support the CALT stimulation during OSDs. However, while an involvement of the CALT in OSDs is hypothesizable, the exact role of this structure in their pathogenesis remains unclear and warrants further investigations.

Age-related Defects in Ocular and Nasal Mucosal Immune System and the Immunopathology of Dry Eye Disease

Dry eye disease (DED) is a prevalent public health concern that affects up to 30% of adults and is particularly chronic and severe in the elderly. Two interconnected mechanisms cause DED: (1) an age-related dysfunction of lacrimal and meibomian glands, which leads to decreased tear production and/or an increase in tear evaporation; and (2) an age-related uncontrolled inflammation of the surface of the eye triggered by yet-to-be-determined internal immunopathological mechanisms, independent of tear deficiency and evaporation. In this review we summarize current knowledge on animal models that mimic both the severity and chronicity of inflammatory DED and that have been reliably used to provide insights into the immunopathological mechanisms of DED, and we provide an overview of the opportunities and limitations of the rabbit model in investigating the role of both ocular and nasal mucosal immune systems in the immunopathology of inflammatory DED and in testing novel immunotherapies aimed at delaying or reversing the uncontrolled age-related inflammatory DED.

Safety and comfort evaluation of a new formulation of Visine(®) lubricant eye drops containing HydroBlend™ and GentlePur™

PURPOSE

To evaluate the clinical safety and comfort of a new benzalkonium chloride-free Visine(®) lubricant eye drop formulation (Hydroblend™ and GentlePur™) in healthy and dry eye subjects.

METHODS

This was a single-site, open-label clinical study comprised of 22 healthy and 22 dry eye subjects. Subjects were instructed to instill 1-2 drops of the test product four times a day for 2 weeks and were examined at visit 1 (day 0), visit 2 (day 7), and visit 3 (day 14). Assessments at each visit included postdosing product usage comfort scores, predosing fluorescein corneal staining score, predosing visual acuity, and pre- and postdosing ocular structure change using slit-lamp biomicroscopy. Adverse events were monitored throughout the course of the study.

RESULTS

Throughout the 14 days of the trial period, subjects from both healthy and dry eye groups rated the eye drops as "very comfortable". For dry eye group, the mean product usage comfort scores for the first 3 minutes postdosing ranged from 8.5 to 8.8 at visit 1 and 9.2 to 9.6 at visit 3 on a 0-10 point scale, with 0 being very uncomfortable and 10 being very comfortable. The mean corneal staining scores over five corneal regions changed from 0.65 at visit 1 to 0.39 at visit 3 for dry eye group. The individual region corneal staining scores were also decreased from visits 1 to 3 for dry eye group. All subjects maintained pretreatment means visual acuity at visits 2 and 3. Biomicroscopic examination indicated no structural changes at all visits. There were no significant adverse events reported during the course of the study.

CONCLUSION

The study confirms that GentlePur™ is an appropriate choice as a preservative for ocular application. The new formulation was safe and comfortable when used four times a day in healthy and dry eye subjects.

Cyclosporine ophthalmic emulsions for the treatment of dry eye: a review of the clinical evidence

Dry eye has gained recognition as a public health problem given its high prevalence, morbidity and cost implications. Although dry eye is common and affects patients' quality of life, only one medication, cyclosporine 0.05% emulsion, has been approved by the US FDA for its treatment. In this review, we summarize the basic science and clinical data regarding the use of cyclosporine in the treatment of dry eye. Randomized controlled trials showed that cyclosporine emulsion outperformed vehicles in the majority of trials, consistently decreasing corneal staining and increasing Schirmer scores. Symptom improvement was more variable, however, with ocular dryness shown to be the most consistently improved symptom over vehicle.

[Testosterone reduces the expression of keratinization-promoting genes in murine Meibomian glands]

BACKGROUND

Extensive keratinization appears to play a major role in the dysfunction of the Meibomian gland. This article presents the potential impact of androgens on limiting keratinization in this tissue, thus, contributing to normal Meibomian gland function and a healthy ocular surface.

MATERIALS AND METHODS

Orchidectomized mice were systemically treated with either testosterone or placebo for 2 weeks. The mRNA was then extracted from the Meibomian glands and differential gene expression was investigated by microarray hybridization and evaluation with GeneSifter software as well as gene ontology information from the Gene Ontology (GO) Consortium.

RESULTS

By z-score calculations, keratinization was the most significantly gene ontology term influenced by testosterone based on down-regulated genes in the mouse Meibomian gland. In particular, under the influence of testosterone the genes coding for small proline-rich protein (Sprr) 2a, Sprr 2b, Sprr 3, keratins 6a and 17 and periplakin were significantly down-regulated, while Sprr 1a and Sprr 2f were significantly up-regulated.

CONCLUSIONS

Testosterone down-regulates the expression of genes promoting keratinization in the Meibomian gland. This may help to prevent Meibomian gland dysfunction by limiting excessive keratinization of this tissue and the adjacent lid margins. The findings elucidate, at least in part, the beneficial impact of androgens on Meibomian gland function and thus on th e health of the ocular surface.

The role of corneal innervation in LASIK-induced neuropathic dry eye

Almost half the patients who undergo laser in situ keratomileusis (LASIK) experience dry eye following the procedure. However, the etiology of LASIK-induced dry eye is unclear. The purpose of this review is to examine and summarize the current evidence for the etiology of LASIK-induced dry eye, with a focus on ocular surface sensitivity and corneal innervation. Evidence suggests that the alteration of corneal nerves after LASIK is the most likely cause of the subjective symptoms of LASIK-induced dry eye, even though corneal sensitivity and the clinical indicators of dry eye return to apparently normal values within a year due to the partial recovery of the corneal nerve plexus. The hypothesis is explored that dry eye symptoms following LASIK may result from abnormal sensation due to LASIK-induced corneal neuropathy. Other factors, such as alterations in conjunctival goblet cell density, might also contribute to the symptoms and signs of LASIK-induced dry eye. Inter-relationships between nerve morphology, tear neuropeptide levels and dry eye require further investigation. A better understanding of this phenomenon may result in improved management of post-LASIK dry eye.

Dry eye disease and microbial keratitis: is there a connection?

Dry eye is a common ocular surface disease of multifactorial etiology characterized by elevated tear osmolality and inflammation leading to a disrupted ocular surface. The latter is a risk factor for ocular surface infection, yet overt infection is not commonly seen clinically in the typical dry eye patient. This suggests that important innate mechanisms operate to protect the dry eye from invading pathogens. This article reviews the current literature on epidemiology of ocular surface infection in dry eye patients and laboratory-based studies on innate immune mechanisms operating at the ocular surface and their alterations in human dry eye and animal models. The review highlights current understanding of innate immunity in dry eye and identifies gaps in our knowledge to help direct future studies to further unravel the complexities of dry eye disease and its sequelae.

Effect of TGF-β on ocular surface epithelial cells

A role for transforming growth factor (TGF)-β in the pathogenesis of some ocular surface diseases has been proposed. We determined if secretion of TGF-β and expression of TGF-β receptors RI, RII, and RIII by human ocular surface epithelial cells were modified under inflammatory conditions. We also determined how these cells responded to TGF-β. A human corneal epithelial (HCE) cell line and a conjunctival epithelial cell line (IOBA-NHC) were exposed to TGF-β1 and -β2 and to proinflammatory cytokines. TGF-β receptor mRNAs were analyzed by real time reverse transcription polymerase chain reaction (RT-PCR) in both cell lines, and in conjunctival, limbal, and corneal epithelial cells from post-mortem human specimens. Expression of TGF-β receptors and pSMAD2/SMAD2 were determined by Western blot and immunofluorescence assays. Secretion of TGF-β isoforms, cytokine/chemokine, and metalloproteinases (MMPs) were analyzed in cell supernatants by immunobead-based assays. Secretory leukocyte proteinase inhibitor (SLPI) secretion was analyzed by enzyme-linked immunosorbent assay. TGF-β isoform and receptor gene expression was determined by RT-PCR in conjunctival epithelium of dry eye (DE) patients and healthy subjects. Our results showed that TGF-β RI expression was down-regulated with IL-4 exposure, whereas TGF-β RII and TGF-β2 were upregulated by TNF-α in HCE cells. TGF-β RIII receptor expression was upregulated in IOBA-NHC cells by TNF-α and IFN-γ. SMAD2 phosphorylation occurred in HCE and IOBA-NHC cells after TGF-β treatment. TGF-β significantly up- and down-regulated secretion of several cytokines/chemokines by both cell lines and MMP by HCE cells. TGF-β2 and TGF-β3 were upregulated and TGF-β RIII mRNA was down-regulated in DE conjunctival epithelium. These results show that TGF-β plays an important role in directing local inflammatory responses in ocular surface epithelial cells.

Molecular mechanism of proinflammatory cytokine-mediated squamous metaplasia in human corneal epithelial cells

PURPOSE

The cornified envelope protein small proline-rich protein 1B (SPRR1B) is a biomarker for squamous metaplasia. Proinflammatory cytokines IL-1beta and IFN-gamma are potent inducers of ocular surface keratinization and SPRR1B expression. Here the molecular mechanisms controlling SPRR1B gene expression in response to IL-1beta and IFN-gamma are elucidated.

METHODS

A 3-kb fragment of the SPRR1B gene 5'-flanking region was amplified from human chromosome 1, sequentially deleted, and cloned into a luciferase vector. Constructs were transiently transfected into human corneal epithelial cells, and activity was assessed in response to IL-1beta, IFN-gamma, or basal medium. Functional cis-elements responding to IL-1beta and IFN-gamma were characterized by site-directed mutagenesis and gel mobility shift assay. Effects of mitogen-activated protein kinases p38, ERK, and JNK were assessed using inhibitors and dominant-negative mutants. Results were validated by real-time RT-PCR.

RESULTS

The first 620 bp of the SPRR1B 5'-flanking region regulated constitutive expression and increased promoter activity in response to IL-1beta and IFN-gamma. Corresponding cis-elements for IL-1beta and IFN-gamma were bound by cAMP response element binding protein (CREB) and zinc-finger E-box binding homeobox 1 (ZEB1), respectively. Inhibition of p38 abolished the stimulatory effects of IL-1beta and IFN-gamma on SPRR1B, whereas inhibition of JNK and ERK had no effect. Dominant-negative mutants targeting p38alpha and p38beta2 blocked cytokine-induced SPRR1B promoter activity and mRNA expression.

CONCLUSIONS

SPRR1B is upregulated by the proinflammatory cytokines IL-1beta and IFN-gamma via p38 MAPK-mediated signaling pathways that lead to the activation of transcription factors CREB and ZEB1, respectively. These results identify key intracellular signaling intermediates involved in the pathogenesis of immune-mediated ocular surface squamous metaplasia.

Acidic mammalian chitinase in dry eye conditions

PURPOSE

An acidic mammalian chitinase (AMCase) seems to be implicated in allergic asthma and allergic ocular pathologies. The aim of this work was to investigate the role of AMCase during Sjögren's Syndrome (SS) and Meibomian Gland Dysfunction (MGD) dry eye diseases.

METHODS

Six patients with MGD dry eye (20-58 years, median 40) and six patients with dry eye associated to SS (32-60 years, median 47) were enrolled in this study. AMCase activity was measured in tears and AMCase mRNA expression was evaluated by real-time polymerase chain reaction from RNA extracted from epithelial cells of the conjunctiva. Six healthy adult subjects of the same age (34-44 years, median 39) were also studied as the control group.

RESULTS

AMCase activity was significantly increased in patients affected by MGD dry eye (18.54 +/- 1.5 nmol/ml/h) and SS dry eye (8.94 +/- 1.0 nmol/ml/h) respectively, compared to healthy controls (1.6 +/- 0.2 nmol/ml/h). AMCase activity was higher in the tears of subjects with MGD dry eye (P < 0.001). AMCase mRNA was detected in conjunctival epithelial cells and the expression was significantly higher in MGD dry eye than SS dry eye. A significant correlation between AMCase activity in the tears and mRNA in conjunctival epithelial cells was found.

CONCLUSION

AMCase may be an important marker in the pathogenesis of dry eye, suggesting the potential role of AMCase as a therapeutic target in these frequent pathologies.

Prevalence of dry eye disease among US men: estimates from the Physicians' Health Studies

OBJECTIVE

To estimate the prevalence and risk factors for dry eye disease (DED) among US men.

METHODS

Cross-sectional prevalence survey among male participants 50 years and older in the Physicians' Health Studies I (N = 18,596) and II (N = 6848). We defined DED as the presence of clinically diagnosed dry eye or severe symptoms (both dryness and irritation constantly or often). We calculated the age-standardized prevalence of DED adjusted to the age distribution of US men in 2004 and projected estimates forward to 2030. We compared DED prevalence with a similar cohort of women and examined associations with possible risk factors.

RESULTS

The prevalence of DED increased with age, from 3.90% among men aged 50 to 54 years to 7.67% among men 80 years and older (P for trend <.001). High blood pressure (odds ratio, 1.28; 95% confidence interval, 1.12-1.45) and benign prostatic hyperplasia (odds ratio, 1.26; 95% confidence interval, 1.09-1.44) were associated with a higher risk of DED. Use of antidepressants, antihypertensives, and medications to treat benign prostatic hyperplasia were also associated with increased risk of DED. The age-standardized prevalence of DED was 4.34%, or 1.68 million men 50 years and older, and is expected to affect more than 2.79 million US men by 2030.

CONCLUSIONS

Dry eye disease is prevalent and increases with age, hypertension, benign prostatic hyperplasia, and antidepressant use.

Glycogene expression in conjunctiva of patients with dry eye: downregulation of Notch signaling

PURPOSE

Glycoconjugates regulate a variety of biological events in mucosal surfaces, such as differentiation of postmitotic epithelial cells and maintenance of the wet-surfaced phenotype. This study aimed to identify the repertoire of genes (glycogenes) involved in biosynthesis of glycoconjugates in conjunctiva of normal subjects and patients with dry eye.

METHODS

RNA from conjunctival impression cytology samples was amplified and hybridized to a custom-designed glycogene microarray. Intensity data were converted to expression values and analyzed by ANOVA. Microarray data for selected Notch glycogenes were confirmed by quantitative real-time PCR. Notch receptors and ligands were immunolocalized on conjunctival biopsies by confocal microscopy.

RESULTS

By microarray, 424 glycogenes were identified in normal conjunctival epithelium; galectins, glycosyltransferases, mucins, Notch signaling molecules, and proteoglycans were among the most highly expressed. In dry eye, 46 glycogenes were significantly downregulated, including five members of the Notch signaling pathway (Notch1, Notch 2, Notch 3, Jagged1, Delta1), four Wnt signaling molecules (Wnt4, -5A, Frizzled6, -7), and three heparan sulfate glycotransferases (HS2ST1, HS3ST6, EXTL2). Only interferon-induced transmembrane protein 1 was upregulated. By real-time PCR, expression ratios of Notch1, Notch 3, and Jagged1 in dry eye were 0.43, 0.56, and 0.50, respectively, compared to controls (P < 0.05). Notch1, Notch3, and Jagged1 were immunolocalized throughout the conjunctival epithelium, whereas Notch2 and Delta1 were distributed apically.

CONCLUSIONS

This study revealed the differential glycogene expression profiles in normal subjects and patients with dry eye. Downregulation of Notch signaling in dry eye may result in abnormal differentiation of the conjunctival epithelium and have implications in the pathogenesis of the disease.

Small proline-rich protein 1B (SPRR1B) is a biomarker for squamous metaplasia in dry eye disease

PURPOSE

Squamous metaplasia occurs in ocular surface diseases like Sjögren's syndrome (SS). It is a phenotypic change whereby epithelial cells initiate synthesis of squamous cell-specific proteins such as small proline-rich protein 1B (SPRR1B) that result in pathologic keratin formation on the ocular surface. The authors hypothesized that inflammation is a key inducer of pathologic keratinization and that SPRR1B represents an analytical biomarker for the study of the molecular mechanisms.

METHODS

Real-time quantitative RT-PCR and immunohistochemistry were used to examine SPRR1B mRNA and protein in two different mouse models of dry eye and patients with SS. Adoptive transfer of mature lymphocytes from mice lacking the autoimmune regulator (aire) gene was performed to examine the role of inflammation as an inducer of squamous metaplasia. SPRR1B expression in response to several cytokines was examined in vitro, whereas the expression of cytokines IL1beta and IFNgamma was quantified in ocular tissues of aire-deficient mice and patients with SS.

RESULTS

SPRR1B was increased across the ocular surface of mice with both desiccating stress and autoimmune-mediated, aqueous-deficient dry eye and in patients with SS. Adoptive transfer of CD4(+) T cells from aire-deficient mice to immunodeficient recipients caused advanced ocular surface keratinization. IL1alpha, IL1beta, IL6, IFNgamma, and TNFalpha induced SPRR1B expression in vitro and the local expression of IL1beta and IFNgamma was elevated in ocular tissues of patients with SS and aire-deficient mice.

CONCLUSIONS

SPRR1B is a valid biomarker for the study of the molecular mechanisms of squamous metaplasia. There is a definitive link between inflammation and squamous metaplasia in autoimmune-mediated dry eye disease, with IL1beta and IFNgamma likely acting as key participants.