Exposure to a dry environment induces strain-specific responses in mice

One Soul and Several Faces of Evaporative Dry Eye Disease

The ocular surface system interacts with, reacts with, and adapts to the daily continuous insults, trauma, and stimuli caused by direct exposure to the atmosphere and environment. Several tissue and para-inflammatory mechanisms interact to guarantee such an ultimate function, hence maintaining its healthy homeostatic equilibrium. Evaporation seriously affects the homeostasis of the system, thereby becoming a critical trigger in the pathogenesis of the vicious cycle of dry eye disease (DED). Tear film lipid composition, distribution, spreading, and efficiency are crucial factors in controlling water evaporation, and are involved in the onset of the hyperosmolar and inflammatory cascades of DED. The structure of tear film lipids, and subsequently the tear film, have a considerable impact on tears' properties and main functions, leading to a peculiar clinical picture and specific management.

Protective effects of low-molecular-weight components of adipose stem cell-derived conditioned medium on dry eye syndrome in mice

The present study demonstrated the protective effects of low-molecular-weight adipose-derived stem cell-conditioned medium (LADSC-CM) in a mouse model of dry eye syndrome. Mice subjected to desiccating stress and benzalkonium chloride had decreased tear secretion, impaired corneal epithelial tight junction with microvilli, and decreased conjunctival goblet cells. Topical application of adipose-derived stem cell-conditioned medium (ADSC-CM) stimulated lacrimal tear secretion, preserved tight junction and microvilli of the corneal epithelium, and increased the density of goblet cells and MUC16 expression in the conjunctiva. The low-molecular-weight fractions (< 10 kDa and < 3 kDa) of ADSC-CM (LADSC-CM) provided better protections than the > 10 kDa or > 3 kDa fractions of ADSC-CM. In the in vitro study, desiccation for 10 min or hyperosmolarity (490 osmols) for 24 h caused decreased viability of human corneal epithelial cells, which were reversed by LADSC-CM. The active ingredients in the LADSC-CM were lipophobic and stable after heating and lyophilization. Our study demonstrated that LADSC-CM had beneficial effects on experimental dry eye. It is worthy of further exploration for the active ingredient(s) and the mechanism.

Inducing dry eye disease using a custom engineered desiccation system: Impact on the ocular surface including keratin-14-positive limbal epithelial stem cells

PURPOSE

Dry eye disease (DED) is characterized by loss of tear film stability that becomes self-sustaining in a vicious cycle of pathophysiological events. Currently, desiccation stress (DS) is the dominant procedure for inducing DED in mice, however its' effect on limbal epithelial stem cells (LESCs) has been overlooked. This study aimed to establish a DS model via the use of a novel hardware to investigate the impact on the ocular surface including LESCs.

METHODS

A mouse transporter unit was customized to generate a dehumidified environment. C57BL/6J mice were exposed to mild DS and injected with scopolamine hydrobromide (SH) or remained untreated (UT) under standard vivarium conditions for 10 consecutive days (n = 28/group). Clinical assessments included phenol red tear-thread test, fluorescein staining and optical coherence tomography assessments. Histopathological and immunofluorescence was used to evaluate tissue architecture, goblet cell (GC) status, lacrimal gland (LG) inflammation and epithelial phenotype on the ocular surface. Whole flat-mounted corneas were immunostained for keratin-14 (K14), then imaged by confocal microscopy and analyzed computationally to investigate the effect of DS on LESCs.

RESULTS

Custom modifications made to the animal transporter unit resulted in dehumidified cage relative humidity (RH) of 43.5 ± 4.79% compared to the vivarium 53.9 ± 1.8% (p = 0.0243). Under these conditions, aqueous tear production in mice was suppressed whilst corneal permeability and corneal irregularity significantly increased. H&E staining indicated stressed corneal basal epithelial cells and increased desquamation. DS-exposed mice had reduced GC density (41.0 ± 5.10 GC/mm vs 46.9 ± 3.88 GC/mm, p = 0.0482) and LGs from these mice exhibited elevated CD4⁺ cell infiltration compared to controls. DS elicited K14⁺ epithelial cell displacement, as indicated by increased fluorescence signal at a distance of 50-100 μm radially inwards from the limbus [0.63 ± 0.053% (DS) vs 0.54 ± 0.060% (UT), p = 0.0317].

CONCLUSIONS

Application of mild DS using customized hardware and SH injections generated features of DED in mice. Following DS, ocular surface epithelial cell health decreased and LESCs appeared stressed. This suggested that potential downstream effects of DS on corneal homeostasis are present, a phenomenon that is currently under-investigated. The method used to induce DED in this study enables the development of a chronic model which more closely resembles disease seen in the clinic.

Esculetin protects human corneal epithelial cells from oxidative stress through Nrf-2 signaling pathway

Dry eye formation often originates from oxidative damage to the ocular surface, which can be caused by external environment or internal pathologic factors. Esculetin (6, 7-dihydroxycoumarin) is a natural product found in many plants, and has been reported to have multiple pharmacological activities. The objective of our present study is to investigate if esculetin could protect the corneal epithelial cells from oxidative damages and its underlying antioxidant molecular mechanisms. Our experimental results demonstrated that pretreatment with esculetin markedly increased the cell viability while decreased the apoptosis in H₂O₂-treated human corneal epithelial (HCE) cells, by regulating Bcl-2, Bax and caspase-3 protein expressions and by altering the imbalance of activities of intracellular reactive oxygen species (ROS) and superoxide dismutase (SOD). Our data revealed that esculetin played an antioxidant role not only through its antioxidant activity, but also by highly inducing Nrf-2 translocation to the nucleus, which in turn, enhanced Nrf2 signaling regulated antioxidant genes (HO-1, NQO1, GCLM, SOD1 and SOD2) mRNA expression levels in H₂O₂-treated HCE cells. In the present study, the protective effects of esculetin on the corneal epithelium were also confirmed by a murine desiccating stress induced dry eye model in vivo. These data illustrated, for the first time, that esculetin may have the ability to protect human corneal epithelial cells from oxidative damages through its scavenging of free radical properties and through the activation of Nrf2 signaling.

Cause and Treatment of Exophthalmos in Aged Cotton Rats (Sigmodon hispidus)

Aged cotton rats (Sigmodon hispidus) from an established breeding colony displayed signs of spontaneous exophthalmos. Of a total of 118 colony animals that were older than 6 mo of age, 37 (31%) displayed signs of exophthalmos. These rats were clinically healthy and had no other signs of disease. Ophthalmic exams, molecular and microbiologic testing, and histopa- thology were performed to determine the cause of the exophthalmos and to provide appropriate treatment. Environmental monitoring records were also reviewed for vivarium rooms in which the cotton rats were housed. Histopathology findings supported that the exophthalmos in these cotton rats was secondary to retro-orbital thrombosis associated with cardiomyopathy. The exophthalmic eyes were treated by either removal of the affected eye (enucleation) or surgical closure of the eyelids (temporary tarsorraphy). Enucleation of the exophthalmic eye was the best intervention for these aged cotton rats. These findings demonstrate the potential for a high incidence of ocular problems occurring secondary to cardiomyopathy in aged cotton rats. Enucleation as a therapeutic intervention for exophthalmic eyes in aged cotton rats prolongs the morbidity-free time span during which these aged animals can be used experimentally.

Evaluation of Corneal Damage After Lacrimal Gland Excision in Male and Female Mice

Purpose

Lacrimal gland excision (LGE) has been utilized in several studies to model aqueous tear deficiency, yet sex as a biological variable has not been factored in to these reports. This study compared corneal pathology in male and female mice following LGE-induced dry eye.

Methods

An LGE of either the extraorbital lacrimal gland (single LGE) or both the extraorbital and intraorbital lacrimal glands (double LGE) was performed in male and female C57BL/6J and Balb/cJ mice to produce dry eye of graded severity. Following excision, tearing was evaluated with phenol red thread, and corneal fluorescein staining was scored to quantify the severity of damage. Corneas were evaluated for apoptosis by the TUNEL assay and for cell proliferation using Ki67 staining. Furthermore, corneas were harvested and analyzed for macrophages via flow cytometry.

Results

Baseline tearing levels were similar in male and female mice, and LGE resulted in comparable reductions in tearing with the lowest levels recorded after double LGE. As determined by fluorescein staining, LGE produced more severe damage to the cornea in female C57BL/6J and Balb/cJ mice. Double LGE increased TUNEL and Ki67 staining in the cornea, with greater increases found in female mice. Furthermore, LGE produced a greater increase in the total number of corneal macrophages in female mice.

Conclusions

These results indicate that female mice are more susceptible to LGE-induced corneal damage. The mechanisms involved in producing these sex differences still need to be elucidated but may involve increased inflammation and macrophage infiltration.

Dose-dependent benzalkonium chloride toxicity imparts ocular surface epithelial changes with features of dry eye disease

PURPOSE

Inclusion of the preservative benzalkonium chloride (BAC) in ophthalmic solutions is prevalent, despite the noted potential for exacerbating dry eye disease (DED). Whilst studies incorporating BAC have assessed its' effects as a mouse model of DED, the impact on limbal epithelia is under-studied. Our investigation aimed to comprehensively assess the impact of different BAC dosing regimens and their suitability as a mouse model of DED.

METHODS

C57BL/6J mice (n = 72) were administered topical BAC (0.05-0.2%) over 7 days. Fluorescein staining, corneal smoothness index, and immuno-histological analyses were applied to determine architectural and cellular changes on the ocular surface following BAC treatment. The effect of BAC (0.0001-0.01%) on cultivated primary mouse corneo-limbal epithelial cells (CLECs) (n = 6) was examined using morphological and functional assays.

RESULTS

Whilst 0.2% BAC induced severe corneal epithelial defects, 0.1% BAC dispensed once daily over 7 days, induced punctate fluorescein staining without detriment to corneal smoothness. Histochemical staining revealed disorganized basal corneal epithelial cells with enlarged cytoplasmic halos. Furthermore, PAS⁺ goblet cells were decreased. BAC treatment also modulated K14 expression and distribution within the limbus. In cultured CLEC, BAC triggered cell contraction and vacuolation, increased LDH release and elevated cell necrosis by 4.1-fold. Concentrations of BAC as low as 0.0001% decreased colony formation.

CONCLUSIONS

This study describes how exposing C57BL/6 mice to BAC induce some clinicopathological features of DED seen in humans, and therefore provides the foundations to explore the consequences on the ocular surface, particularly on limbal epithelia and its' stem cells.

Mouse strains and sexual divergence in corneal innervation and nerve regeneration

A variety of mouse strains and sexes are used in studies of corneal wound healing and nerve regeneration. However, there is a gap of knowledge about corneal nerve density and its function in different mouse strains and sexes. In this study, we report a strain divergence of total and substance P (SP) sensory corneal nerves in uninjured mice. The BALB/c mouse showed the highest nerve density, corneal sensitivity, and tear volume followed by CFW and then C57BL/6. No differences were found in total nerves and SP-positive nerves between sexes. After injury damaged the corneal nerves, an important role for mouse strains, biologic sex, and their association to corneal nerve regeneration was identified. All female mice have a faster nerve regeneration rate than males. The molecular mechanism of this sexual divergence involves higher secretion neurotrophic factors in tears, which in turn modulate gene expression in trigeminal ganglion neurons. An important upstream signaling regulator was β-estradiol, and topical treatment with β-estradiol confirmed its function in corneal nerve regeneration. In conclusion, our study shows that the strain and sex of laboratory mice significantly affect the different indicators of corneal innervation and nerve regeneration. Researchers investigating corneal diseases should carefully consider these factors.—Pham, T. L., Kakazu, A., He, J., Bazan, H. E. P. Mouse strains and sexual divergence in corneal innervation and nerve regeneration.

Pathological conversion of regulatory T cells is associated with loss of allotolerance

CD4+CD25+Foxp3+ Regulatory T cells (Tregs) play a critical role in immune tolerance. The plasticity and functional adaptability of Tregs in an inflammatory microenvironment has been demonstrated in autoimmunity. Here, using a double transgenic mouse model that permits Foxp3 lineage tracing, we investigated the phenotypic plasticity of Foxp3+ Tregs in a well-characterized murine model of corneal transplantation. In order to subvert the normal immune privilege of the cornea and foster an inflammatory milieu, host mice were exposed to desiccating stress prior to transplantation. Treg frequencies and function were decreased following desiccating stress, and this corresponded to decreased graft survival. A fraction of Tregs converted to IL-17+ or IFNγ+ 'exFoxp3' T cells that were phenotypically indistinguishable from effector Th17 or Th1 cells, respectively. We investigated how Foxp3 expression is modulated in different Treg subsets, demonstrating that neuropilin-1- peripherally-derived Tregs are particularly susceptible to conversion to IL-17+/IFNγ+ exFoxp3 cells in response to cues from their microenvironment. Finally, we show that IL-6 and IL-23 are implicated in the conversion of Tregs to exFoxp3 cells. This report demonstrates that the pathological conversion of Tregs contributes to the loss of corneal immune privilege.

Topical Application of Naltrexone to the Ocular Surface of Healthy Volunteers: A Tolerability Study

PURPOSE

A short-term, randomized double-masked study was conducted to test the tolerability of topical application of naltrexone to the corneal surface.

METHODS

Healthy human volunteers were recruited at the Penn State Hershey Medical Center between 2010 and 2013. Study groups of 4 subjects were established to receive escalating dosages of naltrexone; within each group, 1 subject received placebo. Four drops of 4 different dosages of naltrexone dissolved in commercial moxifloxacin solution were administered over a 24-h period of time; 1 group of subjects received only 1 drop. The naltrexone dosages tested were 1 × 10(-6) M (1 drop), 1 × 10(-6) M (4 drops), 5 × 10(-6) M (4 drops), 1 × 10(-5) M (4 drops), and 5 × 10(-5) M (4 drops). Drops were administered over a 24-h period. Consenting subjects had complete eye examinations, including visual acuity (ETDRS), external and slit-lamp examinations, corneal sensitivity, pachymetry, corneal topography, endothelial specular microscopy, Schirmer testing with anesthetic, and fundus photography, before receiving naltrexone. Individuals were reexamined at 24 h and 7 days following naltrexone or placebo application.

RESULTS

Twenty subjects were recruited for the study; 62% were male, 90% were Caucasian; and 19 subjects completed the study. No significant differences were noted in ocular health between left (treated) and right (untreated) eyes of subjects receiving naltrexone or placebo. No significant adverse events were reported.

CONCLUSIONS

Topical naltrexone was well tolerated in healthy human subjects after 1 or 4 eye drops of naltrexone at dosages up to 50 μM administered over a 24-h treatment period and observed for 1 week.

The core mechanism of dry eye disease is inflammation

PURPOSE

The purpose of this article is to review the evidence for the hypothesis that the core mechanism of dry eye disease (DED) is inflammation, including evidence from recent basic, clinical, and translational research involving human patients, animal models, and cell cultures.

METHODS

Using the key words "dry eye + inflammation," the authors conducted a comprehensive search of the PubMed and Web of Science databases for scientific articles published in English between January 1, 1900 and August 30, 2013 on the role of inflammation in DED in cell cultures, animal models, and humans. The resulting articles were then categorized and reviewed.

RESULTS

The literature search revealed a total of 458 publications, almost all published after 1992. The percentages of original studies and review articles are 77.29% (354) and 22.71% (104), respectively. Among the original studies, the number of reports on human DED is 200 (43.7%), on animal models is 115 (25.1%), and cell cultures is 39 (8.5%). A yearly distributing plot revealed that 76% were published from 2003 to 2011, 53% from 2008 to 2012, and 11% during the first 9 months of 2013. This distribution signifies a rapidly growing awareness of the importance of inflammation in DED pathogenesis.

CONCLUSIONS

Inflammation plays a key role in the pathogenesis of DED as evidenced by research using tissue culture, animal models, and subjects with DED. Developing biomarkers for inflammation of the ocular surface will provide improved understanding of the mechanisms leading to DED, classification of the severity of DED, and objective metrics for outcome measures of treatment. The chronicity of the disease suggests that dysregulation of immune mechanisms leads to a cycle of continued inflammation, accompanied by alterations in both innate and adaptive immune responses. Given the underlying mechanism for DED, developing effective and safe anti-inflammatory treatments is likely to be beneficial for patients with DED.

The ocular surface phenotype of Muc5ac and Muc5b null mice

PURPOSE

Recent development of mice null for either Muc5ac or Muc5b mucin allows study of their specific roles at the mouse ocular surface. A recent report indicated that Muc5ac null mice show an ocular surface phenotype similar to that seen in dry eye syndrome. The purpose of our study was to determine the effect of lack of Muc5ac or Muc5b on the ocular surface, and to determine if environmental desiccating stress exacerbated a phenotype.

METHODS

Muc5ac null and Muc5b null mice, and their wild-type controls were examined for ocular surface defects by fluorescein staining. The number of goblet cells per area of conjunctival epithelium was counted, and levels of mucin gene expression and genes associated with epithelial stress, keratinization, and differentiation, known to be altered in dry eye syndrome, were assayed. To determine if the null mice would respond more to desiccating stress than their wild-type controls, they were challenged in a controlled environment chamber (CEC) and assessed for changes in fluorescein staining, tear volume, and inflammatory cells within the conjunctival and corneal epithelia.

RESULTS

Unlike the previous study, we found no ocular surface phenotype in the Muc5ac null mice, even after exposure to desiccating environmental stress. Similarly, no ocular surface phenotype was present in the Muc5b null mice, either before or after exposure to a dry environment in the CEC.

CONCLUSIONS

Our results indicate that deleting either the Muc5ac or Muc5b gene is insufficient to create an observable dry eye phenotype on the ocular surface of these mice.

Tear cytokine profile as a noninvasive biomarker of inflammation for ocular surface diseases: standard operating procedures

PURPOSE

To provide standard operating procedures (SOPs) for measuring tear inflammatory cytokine concentrations and to validate the resulting profile as a minimally invasive objective metric and biomarker of ocular surface inflammation for use in multicenter clinical trials on dry eye disease (DED).

METHODS

Standard operating procedures were established and then validated with cytokine standards, quality controls, and masked tear samples collected from local and distant clinical sites. The concentrations of the inflammatory cytokines in tears were quantified using a high-sensitivity human cytokine multiplex kit.

RESULTS

A panel of inflammatory cytokines was initially investigated, from which four key inflammatory cytokines (IL-1β, IL-6, INF-γ, and TNF-α) were chosen. Results with cytokine standards statistically satisfied the manufacturer's quality control criteria. Results with pooled tear samples were highly reproducible and reliable with tear volumes ranging from 4 to 10 μL. Incorporation of the SOPs into clinical trials was subsequently validated. Tear samples were collected at a distant clinical site, stored, and shipped to our Biomarker Laboratory, where a masked analysis of the four tear cytokines was successfully performed. Tear samples were also collected from a feasibility study on DED. Inflammatory cytokine concentrations were decreased in tears of subjects who received anti-inflammatory treatment.

CONCLUSIONS

Standard operating procedures for human tear cytokine assessment suitable for multicenter clinical trials were established. Tear cytokine profiling using these SOPs may provide objective metrics useful for diagnosing, classifying, and analyzing treatment efficacy in inflammatory conditions of the ocular surface, which may further elucidate the mechanisms involved in the pathogenesis of ocular surface disease.

Spdef null mice lack conjunctival goblet cells and provide a model of dry eye

Goblet cell numbers decrease within the conjunctival epithelium in drying and cicatrizing ocular surface diseases. Factors regulating goblet cell differentiation in conjunctival epithelium are unknown. Recent data indicate that the transcription factor SAM-pointed domain epithelial-specific transcription factor (Spdef) is essential for goblet cell differentiation in tracheobronchial and gastrointestinal epithelium of mice. Using Spdef(-/-) mice, we determined that Spdef is required for conjunctival goblet cell differentiation and that Spdef(-/-) mice, which lack conjunctival goblet cells, have significantly increased corneal surface fluorescein staining and tear volume, a phenotype consistent with dry eye. Microarray analysis of conjunctival epithelium in Spdef(-/-) mice revealed down-regulation of goblet cell-specific genes (Muc5ac, Tff1, Gcnt3). Up-regulated genes included epithelial cell differentiation/keratinization genes (Sprr2h, Tgm1) and proinflammatory genes (Il1-α, Il-1β, Tnf-α), all of which are up-regulated in dry eye. Interestingly, four Wnt pathway genes were down-regulated. SPDEF expression was significantly decreased in the conjunctival epithelium of Sjögren syndrome patients with dry eye and decreased goblet cell mucin expression. These data demonstrate that Spdef is required for conjunctival goblet cell differentiation and down-regulation of SPDEF may play a role in human dry eye with goblet cell loss. Spdef(-/-) mice have an ocular surface phenotype similar to that in moderate dry eye, providing a new, more convenient model for the disease.

Efficacy of topical blockade of interleukin-1 in experimental dry eye disease

PURPOSE

To evaluate the therapeutic efficacy of topical interleukin-1 receptor antagonist (IL-1Ra) in the treatment of dry eye disease.

DESIGN

Laboratory investigation.

METHODS

Dry eye disease was induced in C57BL/6 female mice through exposure to a desiccating environment within a controlled environment chamber. Topical formulations containing 5% IL-1Ra, 1% methylprednisolone, 0.05% cyclosporin A, and a vehicle control containing carboxymethylcellulose sodium were applied after the induction of dry eye. Corneal fluorescein staining was performed by a masked observer in the different treatment groups. Immunohistochemical studies were undertaken to enumerate corneal CD11b+ cells, as well as to evaluate corneal lymphangiogenesis. Real-time polymerase reaction was used to quantify the expression of interleukin-1β in the cornea.

RESULTS

A significant decrease in corneal fluorescein staining was observed after topical treatment with 5% IL-1Ra (P < .01), 1% methylprednisolone (P < .01), and 0.05% cyclosporin A (P < .03). Additionally, a significant decrease in the numbers of central corneal CD11b+ cells (P < .05), corneal lymphatic growth (P < .05), and corneal interleukin-1β expression (P < .003), compared with vehicle treated, were demonstrated only after treatment with 5% IL-1Ra and 1% methylprednisolone, and were absent after cyclosporin A treatment.

CONCLUSIONS

Topical treatment with IL-1Ra is effective in ameliorating the clinical signs of the dry eye disease, as well as in reducing underlying inflammation. These effects are comparable with those resulting from treatment with topical methylprednisolone. Topical IL-1Ra may hold promise as a novel therapeutic strategy in the treatment of dry eye.

Spontaneous episodic decreased tear secretion in rats is related to opioidergic signaling pathways

PURPOSE

To elucidate the factors in tear production, this study examined the role of endogenous opioids and opioid receptors in spontaneous episodic reduced tear volume.

METHODS

A model of spontaneous episodic decreases in the quantity of tears was characterized in otherwise normal Sprague-Dawley rats using Schirmer's test. A single eye drop of 10(-5) M naltrexone (NTX), 10(-5) M [Met(5)]-enkephalin, or sterile vehicle was administered to one eye. Tear secretion, corneal sensitivity, and corneal morphology were examined in both eyes.

RESULTS

At any given time period, otherwise normal rats were found to have Schirmer test scores with a bimodal distribution (6.5 mm or less, or 7.0 mm or greater). Decreased tear production was detected in male and female rats aged 4 to 24 weeks at least once per animal. The episodes of reduced tear volume ranged from 1 to 7 days. No changes in corneal sensitivity or corneal morphology were observed in any rat. One drop of NTX given to rats with a decrease in tear volume raised levels of tears to scores of 7.0 mm or greater within 1 hour, and increased tear production persisted for at least 48 hours. NTX had no effect on rats with Schirmer scores of 7.0 mm or higher. Topical application of [Met(5)]-enkephalin depressed tear secretion from baseline scores of 9.8 ± 0.6 mm to as low as 4.5 ± 0.7 mm.

CONCLUSIONS

Normal rats experience fluctuations in tear production that can be modulated by opioidergic signaling pathways.

Research on the stability of a rabbit dry eye model induced by topical application of the preservative benzalkonium chloride

Background

Dry eye is a common disease worldwide, and animal models are critical for the study of it. At present, there is no research about the stability of the extant animal models, which may have negative implications for previous dry eye studies. In this study, we observed the stability of a rabbit dry eye model induced by the topical benzalkonium chloride (BAC) and determined the valid time of this model.

Methods and Findings

Eighty white rabbits were randomly divided into four groups. One eye from each rabbit was randomly chosen to receive topical 0.1% BAC twice daily for 2 weeks (Group BAC-W2), 3 weeks (Group BAC-W3), 4 weeks (Group BAC-W4), or 5 weeks (Group BAC-W5). Fluorescein staining, Schirmer's tests, and conjunctival impression cytology were performed before BAC treatment (normal) and on days 0, 7, 14 and 21 after BAC removal. The eyeballs were collected at these time points for immunofluorescence staining, hematoxylin and eosin (HE) staining, and electron microscopy. After removing BAC, the signs of dry eye in Group BAC-W2 lasted one week. Compared with normal, there were still significant differences in the results of Schirmer's tests and fluorescein staining in Groups BAC-W3 and BAC-W4 on day 7 (P<0.05) and in Group BAC-W5 on day 14 (P<0.05). Decreases in goblet cell density remained stable in the three experimental groups at all time points (P<0.001). Decreased levels of mucin-5 subtype AC (MUC5AC), along with histopathological and ultrastructural disorders of the cornea and conjunctiva could be observed in Group BAC-W4 and particularly in Group BAC-W5 until day 21.

Conclusions

A stable rabbit dry eye model was induced by topical 0.1% BAC for 5 weeks, and after BAC removal, the signs of dry eye were sustained for 2 weeks (for the mixed type of dry eye) or for at least 3 weeks (for mucin-deficient dry eye).

Oral azithromycin for treatment of posterior blepharitis

PURPOSE

To evaluate the effects of oral azithromycin in patients with posterior blepharitis.

METHODS

Twenty-six eyes of 13 patients with posterior blepharitis diagnosed by a qualified ophthalmologist were enrolled in this study. Patients were instructed to use oral azithromycin 500 mg per day for 3 days in 3 cycles with 7-day intervals. Subjective clinical outcomes were graded and scored 1 day before and 30 days after the end of the treatment (53 days after initiating the treatment) based on severity scores of: (1) eyelid debris; (2) eyelid telangiectasia; (3) swelling of the eyelid margin; (4) redness of the eyelid margin; and (5) ocular mucus secretion. For the assessment of global efficacy, patients were asked by the investigator to rate the subjective symptoms (eyelid itching, ocular itching, eyelid hyperemia, ocular hyperemia, ocular mucus secretion, photophobia, foreign body sensation, and dry eye sensation) on a scale of 0 (no symptoms) to 5 (severe symptoms). Break-up time, Schirmer I test, corneal fluorescein staining score, and rose bengal staining score were also performed in all patients.

RESULTS

All clinical outcomes scoring showed statistically significant improvement after oral azithromycin, except for eyelid swelling. Average subjective symptom grading improved statistically after treatment with oral azithromycin, except for eyelid hyperemia, photophobia, and foreign body sensation. Average tear film break-up time values showed statistically significant improvement after the treatment with oral azithromycin. No statistically significant improvement was observed on average values of Schirmer I test, corneal fluorescein staining score, and rose bengal staining score.

CONCLUSIONS

The combination of multiple clinical parameters shown in this study supports the clinical efficacy of pulsed oral azithromycin therapy for the management of posterior blepharitis.

Lymphotoxin-beta receptor blockade reduces CXCL13 in lacrimal glands and improves corneal integrity in the NOD model of Sjögren's syndrome

Introduction

In Sjögren's syndrome, keratoconjunctivitis sicca (dry eye) is associated with infiltration of lacrimal glands by leukocytes and consequent losses of tear-fluid production and the integrity of the ocular surface. We investigated the effect of blockade of the lymphotoxin-beta receptor (LTBR) pathway on lacrimal-gland pathology in the NOD mouse model of Sjögren's syndrome.

Methods

Male NOD mice were treated for up to ten weeks with an antagonist, LTBR-Ig, or control mouse antibody MOPC-21. Extra-orbital lacrimal glands were analyzed by immunohistochemistry for high endothelial venules (HEV), by Affymetrix gene-array analysis and real-time PCR for differential gene expression, and by ELISA for CXCL13 protein. Leukocytes from lacrimal glands were analyzed by flow-cytometry. Tear-fluid secretion-rates were measured and the integrity of the ocular surface was scored using slit-lamp microscopy and fluorescein isothiocyanate (FITC) staining. The chemokine CXCL13 was measured by ELISA in sera from Sjögren's syndrome patients (n = 27) and healthy controls (n = 30). Statistical analysis was by the two-tailed, unpaired T-test, or the Mann-Whitney-test for ocular integrity scores.

Results

LTBR blockade for eight weeks reduced B-cell accumulation (approximately 5-fold), eliminated HEV in lacrimal glands, and reduced the entry rate of lymphocytes into lacrimal glands. Affymetrix-chip analysis revealed numerous changes in mRNA expression due to LTBR blockade, including reduction of homeostatic chemokine expression. The reduction of CXCL13, CCL21, CCL19 mRNA and the HEV-associated gene GLYCAM-1 was confirmed by PCR analysis. CXCL13 protein increased with disease progression in lacrimal-gland homogenates, but after LTBR blockade for 8 weeks, CXCL13 was reduced approximately 6-fold to 8.4 pg/mg (+/- 2.7) from 51 pg/mg (+/-5.3) in lacrimal glands of 16 week old control mice. Mice given LTBR blockade exhibited an approximately two-fold greater tear-fluid secretion than control mice (P = 0.001), and had a significantly improved ocular surface integrity score (P = 0.005). The mean CXCL13 concentration in sera from Sjögren's patients (n = 27) was 170 pg/ml, compared to 92.0 pg/ml for sera from (n = 30) healthy controls (P = 0.01).

Conclusions

Blockade of LTBR pathways may have therapeutic potential for treatment of Sjögren's syndrome.

sPLA2-IIa amplifies ocular surface inflammation in the experimental dry eye (DE) BALB/c mouse model

PURPOSE

sPLA2-IIa is a biomarker for many inflammatory diseases in humans and is found at high levels in human tears. However, its role in ocular surface inflammation remains unclear. An experimentally induced BALB/c mouse dry eye (DE) model was used to elucidate the role of sPLA2-IIa in ocular surface inflammation.

METHODS

BALB/c mice were subcutaneously injected with scopolamine and placed in a daytime air-drying device for 5 to 10 days. Control mice received no treatment. DE status was evaluated with tear production with a phenol-red thread method. Tear inflammatory cytokines were quantified by multiplex immunoassays. Ocular surface inflammation and sPLA2-IIa expression were examined by immune-staining and quantitative (q)RT(2)-PCR. Conjunctiva (CNJ) of the mice was cultured for prostaglandin E2 production induced by sPLA2-IIa with various amount of sPLA2-IIa inhibitor, S-3319.

RESULTS

Treated mice produced fewer tears and heavier corneal (CN) fluorescein staining than the untreated controls (P < 0.001). They also revealed lower goblet cell density (P < 0.001) with greater inflammatory cell infiltration within the conjunctiva, and higher concentration of tear inflammatory cytokines than the controls. Moreover, treated mice showed heavier sPLA2-IIa immune staining than the controls in the CNJ epithelium, but not in the CN epithelium or the lacrimal gland. Treated mice exhibited upregulated sPLA2-IIa and cytokine gene transcription. Furthermore, CNJ cultures treated with sPLA2-IIa inhibitor showed significantly reduced sPLA2-IIa-induced inflammation.

CONCLUSIONS

This is the first report regarding sPLA2-IIa in the regulation of ocular surface inflammation. The findings may therefore lead to new therapeutic strategies for ocular surface inflammation, such as DE disease.

Dry eye disease as an inflammatory disorder

PURPOSE

Dry eye disease (DED) is a prevalent inflammatory disorder of the lacrimal functional unit of multifactorial origin leading to chronic ocular surface disease, impaired quality of vision, and a wide range of complications, eventually causing a reduction in quality of life. It still is a frustrating disease because of the present scarcity of therapies that can reverse, or at least stop, its progression.

METHODS

A comprehensive literature survey of English-written scientific publications on the role of inflammation in DED.

RESULTS

New investigations have demonstrated that a chronic inflammatory response plays a key role in the pathogenesis of human DED. Additionally, correlations between inflammatory molecules and clinical data suggest that inflammation can be responsible for some of the clinical symptoms and signs.

CONCLUSIONS

Research efforts to clarify its pathophysiology are leading to a better understanding of DED, demonstrating that inflammation, in addition to many other factors, plays a relevant role.

Predicted phenotypes of dry eye: proposed consequences of its natural history

This paper reviews current knowledge of the pathophysiology of dry eye and predicts that the clinical picture in late disease differs in both severity and quality from that in early disease. It is hypothesized that hybrid forms evolve, in which aqueous-deficient dry eye (ADDE) takes on features of evaporative dry eye (EDE) and vice versa. As a consequence, early and late forms may require different diagnostic criteria and respond to different therapeutic regimes. Tear hyperosmolarity plays a key role in the damage mechanism of dry eye, and ADDE is recognized to be a low-volume, hyperosmolar state. As ADDE advances, a progressive decrease in lacrimal secretion occurs, exacerbated by loss of the corneal reflex. This causes a decrease in tear volume, thinning of the aqueous tear film, and retarded spreading of the tear film lipid layer. The latter is hypothesized to cause an increase in evaporative water loss and an added evaporative component to the dry eye. Thus, in advanced disease, the hybrid state would be an organic ADDE, accompanied by a functional EDE in the absence of meibomian gland dysfunction. This functional EDE would respond to agents that expand the tear volume, restore corneal sensitivity, or provide an artificial tear film lipid layer.

Time course of ocular surface and lacrimal gland changes in a new scopolamine-induced dry eye model

BACKGROUND

The aim of this study was to set up an animal model of dry eye showing disturbance in several components of the lacrimal functional unit, and to describe the time course of the appearance of clinical signs and inflammatory markers.

METHODS

Dry eye was induced in 6-week-old female Lewis rats by a systemic and continuous delivery of scopolamine via osmotic pumps implanted subcutaneously. We first determined the appropriate dose of scopolamine (6, 12.5, or 25 mg/day) for 28 days. In a second set of experiments, we determined markers after 1, 2, 3, 7, 10, 17, or 28 days of a 12.5-mg/day dose. Clinical signs of corneal dryness were evaluated in vivo using fluorescein staining. MHC II expression and mucin Muc5AC production were detected on the conjunctival epithelium using immunostaining. The level of IL-1beta, IL-6, TNF-alpha, and IFN-gamma mRNA was evaluated by real-time polymerase chain reaction in conjunctiva and exorbital lacrimal gland (LG). Lipids were extracted from the exorbital LG for fatty acid analysis.

RESULTS

Daily scopolamine doses of 12.5 mg and 25 mg applied for a 28-day period induced keratitis, a decrease in Muc5AC immunostaining density in the conjunctival epithelium, and modifications in the fatty acid composition of the exorbital LG. Animals treated with a 12.5-mg/day dose of scopolamine exhibited an increase in corneal fluorescein staining after 2, 10, and 28 days. All animals exhibited unilateral or bilateral keratitis after 17 days. In the conjunctival epithelium, a significant decrease in Muc5AC immunostaining density was observed at early and late time points, and MHC II expression tended to be increased after 1, 7, 10, and 28 days, without reaching statistical significance. The levels of TNF-alpha, IL-1beta and IL-6 mRNA were increased with scopolamine treatment in both conjunctiva and exorbital LG. Arachidonic acid and the Delta5 desaturase index were significantly increased in the exorbital LG of dry eye animals at each time point.

CONCLUSIONS

This systemic and continuous scopolamine-induced model of dry eye in the rat may represent a helpful tool to investigate moderate dry eye, and makes a contribution in the field of dry eye study.