Interleukin-6 and tumor necrosis factor-alpha levels in tears of patients with dry eye syndrome

Inflammation in Dry Eye Disease-Pathogenesis, Preclinical Animal Models, and Treatments

Dry eye disease (DED) is a rapidly growing ocular surface disease with a significant socioeconomic impact that affects the patients' visual function and, thus, their quality of life. It is distinguished by a loss of tear film homeostasis, leading to tear film instability, hyperosmolarity, ocular surface inflammation, and neurosensory abnormalities, with all of these playing etiological roles in the propagation of the vicious DED circle. While current treatments primarily focus on reducing tear film instability and hyperosmolarity, increasingly more attention is being placed on tackling the underlying inflammation that propagates and potentiates these factors. As such, preclinical models are crucial to further elucidate the DED pathophysiology and develop novel therapeutic strategies. This review outlines the role of inflammation in DED, highlighting related signs and diagnostic tools before focusing on relevant preclinical animal models and potential therapeutic strategies to tackle DED-associated inflammation.

A Rabbit Dry Eye Model Induced by Subcutaneous Scopolamine

PURPOSE

To establish and characterize a dry eye model in New Zealand rabbits by subcutaneous injections of scopolamine hydrobromide (SCOP).

METHODS

Twenty New Zealand male rabbits were injected subcutaneously SCOP for 14 consecutive days; subcutaneous saline was used as a negative control. The correlated clinical parameters of ocular surface dryness were detected in vivo using tear secretion and corneal fluorescein staining. The expression of IL-1β and TNF-α on the ocular surface and in lacrimal glands were analyzed by real-time PCR and western blot on the 14th day. The expression of Mucin-5 subtype AC (MUC5AC) was detected by Immunofluorescence staining in conjunctival tissue.

RESULTS

The SCOP-treated rabbits exhibited significantly decreased aqueous tear secretion and increased corneal fluorescein staining scores over time. Both the mRNA expression levels and the protein expression levels of IL-1β and TNF-α were significantly increased after SCOP treatment compared with those after saline treatment. The loss of conjunctival MUC5AC was found in the SCOP-injected rabbits. Some infiltrated inflammatory cells and atrophic acinar cells were observed in the lacrimal gland after SCOP treatment. The disordered structures of the ocular surface and lacrimal glands were also observed.

CONCLUSIONS

This study showed that repeated subcutaneous SCOP injections successfully elicited some of the typical dry eye symptoms commonly seen in humans.

IL-6 induces Treg dysfunction in desiccating stress-induced dry eye disease

Regulatory T cells (Tregs) play a critical role in maintaining immune homeostasis, and their dysfunction is implicated in the pathogenesis of various autoimmune disorders, including dry eye disease (DED). Treg dysfunction in DED allows T-helper cell 17 (Th17) mediated chronic inflammation at the ocular surface. In this study, the factors causing Treg dysfunction in DED were investigated. We observed reduced expression of Treg functional markers - FoxP3, CD25, and CTLA-4 in the cells isolated from DED mice (DED Tregs). Additionally, DED Tregs showed increased expression levels of receptors for pro-inflammatory cytokine receptors, namely IL-6R, IL-17RA, and IL-23R. An increased expression level of pro-inflammatory cytokine receptors was observed on exposing Tregs isolated from naïve mice (NTregs) to IL-6 or IL-17, but not IL-23, with a concomitant downregulation of FoxP3, CD25, and CTLA-4 in these cells. Furthermore, among these cytokines, IL-6 induced the most pronounced loss of Treg mediated suppression of Th17 proliferation and IL-10 secretion. In vitro and in vivo blockade of IL-6 effectively restored function in DED Tregs, leading to enhanced suppressive function against proliferating Th17 cells and ameliorating disease severity. In conclusion, this study provides insights into mechanisms of Treg dysregulation in DED, specifically delineating the effect of Th17-associated cytokines, with IL-6 emerging as the critical factor inducing Treg dysfunctionality. These findings highlight the potential for developing novel therapeutic interventions for DED through restoration of immunosuppressive function of Tregs.

Evaluating the Efficacy of the Diluted Schirmer Method for Tear Collection in Dry Eye Syndrome Patients

PURPOSE

This study assesses the diluted Schirmer method's effectiveness in collecting tears from dry eye syndrome patients, aiming to identify the most suitable tear collection technique for them.

METHODS

A prospective study. Tear samples were collected from patients with dry eye syndrome and healthy individuals using two methods: (1) Direct Schirmer Method: Schirmer strips were directly inserted into the eye to collect tears. (2) Diluted Schirmer Method: After instilling physiological saline into the eye and waiting for 30 s to ensure thorough mixing with tears, Schirmer strips were used for collection. Tear samples from both groups were analyzed and compared for total protein and cytokine levels (IL-1β, IL-6, IL-8, TNF-α).

RESULTS

(1) The study included 32 participants: 16 with dry eye syndrome (4 males, 12 females, average age 34.92 ± 10.13 years) and 16 healthy controls (5 males, 11 females, average age 32.25 ± 9.87 years). (2) The diluted Schirmer method produced a significantly larger tear volume compared to the direct method (p < 0.05), with lower Visual Analogue Scale (VAS) scores indicating less discomfort (p < 0.05). (3) The average total protein content of the two groups was 51.70 ± 3.166 ng measured by Direct Schirmer method, and the average total protein content of the Diluted Schirmer method was 50.05 ± 3.263 ng. There was no statistical difference between the two groups. (t = 1.051, p = 0.3098) (4) The concentrations of total tear protein and various cytokines measured by both methods were higher in the dry eye group compared to the normal group, with statistically significant differences (p < 0.05). Both methods reflected consistent changes in tear protein profiles.

CONCLUSION

The diluted Schirmer method can comfortably collect an adequate volume of tear samples in a short time and consistently reflect changes in tear proteins, making it an effective method for tear collection in patients with dry eye syndrome.

Tear Fluid Progranulin as a Noninvasive Biomarker for the Monitoring of Corneal Innervation Changes in Patients With Type 2 Diabetes Mellitus

Purpose

This study aimed to investigate the expression levels of progranulin (PGRN) in the tears of patients with diabetic retinopathy (DR) versus healthy controls. Additionally, we sought to explore the correlation between PGRN levels and the severity of ocular surface complications in patients with diabetes.

Methods

In this prospective, single-visit, cross-sectional study, patients with DR (n = 48) and age-matched healthy controls (n = 22) were included and underwent dry eye examinations. Tear fluid was collected, and its components were analyzed using the Luminex assay. The subbasal nerve plexus of all participants was evaluated by in vivo confocal microscopy.

Results

Patients with DR exhibited more severe dry eye symptoms, along with a reduction in nerve fiber density, length, and branch density within the subbasal nerve plexus, accompanied by an increase in the number of dendritic cells. Tear PGRN levels were also significantly lower in patients with diabetes than in normal controls, and the levels of some inflammatory factors (TNF-α, IL-6, and MMP-9) were higher in patients with DR. Remarkably, the PGRN level significantly correlated with nerve fiber density (R = 0.48, P < 0.001), nerve fiber length (R = 0.65, P < 0.001), and nerve branch density (R = 0.69, P < 0.001).

Conclusions

Tear PGRN levels might reflect morphological changes in the corneal nerve plexus under diabetic conditions, suggesting that PGRN itself is a reliable indicator for predicting the advancement of neurotrophic keratopathy in patients with diabetes.

Translational Relevance

PGRN insufficiency on the ocular surface under diabetic conditions was found to be closely associated with nerve impairment, providing a novel perspective to discover the pathogenesis of diabetic complications, which could help in developing innovative therapeutic strategies.

What is the impact of microbiota on dry eye: a literature review of the gut-eye axis

BACKGROUND

Dry eye is a chronic and multifactorial ocular surface disease caused by tear film instability or imbalance in the microenvironment of the ocular surface. It can lead to various discomforts such as inflammation of the ocular surface and visual issues. However, the mechanism of dry eye is not clear, which results in dry eye being only relieved but not cured in clinical practice. Finding multiple environmental pathways for dry eye and exploring the pathogenesis of dry eye have become the focus of research. Studies have found that changes in microbiota may be related to the occurrence and development of dry eye disease.

METHODS

Entered the keywords "Dry eye", "Microbiota", "Bacteria" through PUBMED, summarised the articles that meet the inclusion criteria and then filtered them while the publication time range of the literature was defined in the past 5 years, with a deadline of 2023.A total of 13 clinical and 1 animal-related research articles were screened out and included in the summary.

RESULTS

Study found that different components of bacteria can induce ocular immune responses through different receptors present on the ocular surface, thereby leading to an imbalance in the ocular surface microenvironment. Changes in the ocular surface microbiota and gut microbiota were also found when dry eye syndrome occurs, including changes in diversity, an increase in pro-inflammatory bacteria, and a decrease in short-chain fatty acid-related bacterial genera that produce anti-inflammatory effects. Fecal microbiota transplantation or probiotic intervention can alleviate signs of inflammation on the ocular surface of dry eye animal models.

CONCLUSIONS

By summarizing the changes in the ocular surface and intestinal microbiota when dry eye occurs, it is speculated and concluded that the intestine may affect the occurrence of eye diseases such as dry eye through several pathways and mechanisms, such as the occurrence of abnormal immune responses, microbiota metabolites- intervention of short-chain fatty acids, imbalance of pro-inflammatory and anti-inflammatory factors, and release of neurotransmitters, etc. Analyzing the correlation between the intestinal tract and the eyes from the perspective of microbiota can provide a theoretical basis and a new idea for relieving dry eyes in multiple ways in the future.

Association between dryness sensation and ocular surface temperature and conjunctival blood flow in soft contact lens wearers

PURPOSE

To investigate the association between dryness, ocular surface temperature (OST), and conjunctival blood flow (CBF) in soft contact lens (SCL) wearers after airflow stimulation.

METHODS

After recruiting 21 SCL wearers (mean age, 25.3 ± 4.2 years), subjects used two different daily disposable silicone hydrogel SCLs (narafilcon A and delefilcon A lenses). On three of four measurement days, excluding the first, OST, CBF, tear meniscus height (TMH), and non-invasive tear break-up time (NIBUT) were measured after airflow stimulation at a rate of 3 m/s for 10 min. The measurements were conducted without SCLs on the first and second days, and with different SCLs on the third and fourth days. Dryness was evaluated using the visual analogue scale (VAS). These parameters were compared between the two types of SCLs, and their association with the dryness sensation was then investigated.

RESULTS

Dryness was significantly weakly correlated with OST (r = -0.375, p < 0.05) and CBF (r = 0.339, p < 0.05). TMH, NIBUT, and VAS scores for dryness with the delefilcon A lens (0.15 ± 0.05 mm, 3.7 ± 01.7 s and 29.4 ± 16.9) were significantly higher, longer, and lower, respectively, than those with the narafilcon A lens (0.12 ± 0.05 mm, 2.3 ± 1.7 s and 35.9 ± 17.0; p < 0.05, p < 0.01 and p < 0.01). The changes in the OST and CBF between with and without the delefilcon A lens (-0.36 ± 0.35 °C and 0.99 ± 0.19) were significantly small compared to the narafilcon A lens (-0.60 ± 0.42 °C and 1.11 ± 0.21; p < 0.01 for both comparisons).

CONCLUSION

Dryness was correlated with OST and CBF, which indicates that when dryness was high, OST was low and CBF was high. These results suggest that OST and CBF assessments are effective for evaluating dryness sensation.

Tear film hTERT and corneal nerve characteristics in dry eye disease

CLINICAL RELEVANCE

The behaviour of human telomerase reverse transcriptase (hTERT) in tears reflects its role in maintaining the ocular surface homoeostasis, as it is increased after the initial fitting of contact lenses and post-overnight lid closure.

BACKGROUND

hTERT has been shown to respond to cellular stress in neurodegenerative diseases and to enhance axonal regeneration after peripheral axotomy in an animal model. This work investigated whether the behaviour of hTERT in the tear film reflects ocular surface inflammation and neuronal changes in the presence of dry eye disease.

METHODS

Flush tears were collected from 18 participants with dry eye disease (14 females, 4 males, mean age 34.7 ± 5.2 years) and from 18 healthy participants without dry eye disease (8 females, 10 males, mean age 31.9 ± 5.8 years). Dry eye disease status was defined using the TFOS DEWS II diagnostic criteria. hTERT levels in tears were measured using enzyme-linked immunosorbent assays. Confocal images were taken at the level of the subbasal nerve plexus at the central cornea and at the inferior whorl, and the densities of corneal immune cells were evaluated as well as corneal nerve morphology metrics using a fully automated technique (University of Manchester, United Kingdom).

RESULTS

In participants with dry eye disease, hTERT levels were significantly higher compared to controls (median [interquartile range]: 434 [320-600] ng/ml, and 184 [42-390] ng/ml, respectively, p = 0.01). Increased nerve fibre width at the inferior whorl, was seen in those with dry eyes (0.0219 [0.0214-0.0236] mm/mm compared to controls 0.0217 [0.0207 0.0222] p < 0.001), but no significant differences were found in the density of corneal immune cells.

CONCLUSIONS

hTERT levels were elevated in participants with dry eye disease, and this was accompanied by increased nerve thickness in the inferior cornea. The hTERT response may reflect the stress induced to the ocular surface and corneal nerves due to having dry eye disease.

Safety and Efficacy of Topical Vitamin D in the Management of Dry Eye Disease Associated With Meibomian Gland Dysfunction: A Placebo-Controlled Double-Blind Randomized Controlled Trial

PURPOSE

The aim of this study was to investigate the safety and efficacy of topical vitamin D in the management of dry eye disease associated with meibomian gland dysfunction (MGD).

METHODS

In this randomized controlled trial, patients with symptomatic MGD were divided into 2 groups to receive topical vitamin D drops or placebo in their randomized eyes. The exclusion criteria consisted of patients with vitamin D deficiency, previous ocular surgery, and patients with ocular diseases affecting the tear film. Patients and researchers were masked to the study groups. The outcomes included the score of Dry Eye Questionnaire (DEQ) 5 and Ocular Surface Disease Index (OSDI), corneal and conjunctival staining score, tear breakup time (TBUT), Schirmer, and MG expressibility score evaluated at baseline and weeks 4 and 8.

RESULTS

Twenty-eight eyes of 28 patients were recruited in each group. In addition to the improvement of subjective parameters in both groups, there was a statistically significantly greater improvement in the vitamin D group compared with control for average scores of OSDI (13.38 ± 7.32 vs. 27.94 ± 7.49) and DEQ5 (9.67 ± 1.86 vs. 14.14 ± 2.45) at week 8 (Ps <0.001). In addition, a significant improvement in TBUT and Schirmer test was observed in both groups in weeks 4 and 8 ( P value <0.05). There was a significant difference between the treatment and control groups after 8 weeks for OSDI, DEQ5, Schirmer, TBUT, corneal fluorescein staining, and MG expressibility score ( P value <0.05).

CONCLUSIONS

The preliminary results of this randomized controlled trial suggested that use of topical vitamin D drops with a lipid vehicle could be safe and might significantly improve the symptoms and signs of dry eye associated with MGD.

Efficacy and Safety of Plasma Rich in Growth Factor in Patients with Congenital Aniridia and Dry Eye Disease

Congenital aniridia is a rare bilateral ocular malformation characterized by the partial or complete absence of the iris and is frequently associated with various anomalies, including keratopathy, cataract, glaucoma, and foveal and optic nerve hypoplasia. Additionally, nearly 50% of individuals with congenital aniridia experience symptoms of ocular dryness. Traditional treatment encompasses artificial tears and autologous serum. This study aimed to assess the effectiveness and safety of using platelet rich in growth factors (PRGF) plasma in patients with congenital aniridia and ocular dryness symptoms.

METHODS

The included patients underwent two cycles of a 3-month PRGF treatment. At 6 months, symptomatology was evaluated using the OSDI and SANDE questionnaires, and ocular surface parameters were analyzed.

RESULTS

The OSDI and SANDE values for frequency and severity demonstrated statistically significant improvements (p < 0.05). Ocular redness, corneal damage (corneal staining), and tear volume (Schirmer test) also exhibited statistically significant improvements (p < 0.05). No significant changes were observed in visual acuity or in the grade of meibomian gland loss.

CONCLUSION

The use of PRGF in patients with congenital aniridia and ocular dryness symptoms led to significant improvements in symptomatology, ocular redness, and ocular damage. No adverse effects were observed during the use of PRGF.

Exploration of efficacy and mechanism of 0.05% cyclosporine eye drops (II) monotherapy in allergic conjunctivitis-associated dry eye

PURPOSE

To explore the efficacy and relevant mechanism of 0.05% cyclosporine A (CsA) eye drops (II) monotherapy in patients with allergic conjunctivitis-associated dry eye (ACDE).

METHODS

Prospective, randomized, controlled study. Fifty-three patients with mild-to-moderate ACDE were randomly assigned to two groups. The CsA group received 0.05% CsA eye drops (II) monotherapy four times daily. The control group received 0.1% olopatadine twice daily combined with 0.1% preservative-free artificial tears four times daily. Clinical symptoms and signs, tear total IgE, and lymphotoxin-α (LT-α) concentrations were assessed at pre- and post-treatment days 7, 30, and 60. And we further measured six tear cytokines levels using a microsphere-based immunoassay.

RESULTS

The CsA group showed significant improvement in symptoms (Ocular Surface Disease Index and itching scores) and signs (conjunctival hyperaemia, conjunctival oedema, conjunctival papillae, tear break-up time (TBUT), corneal fluorescein staining, and goblet cell density) at each follow-up period compared to pre-treatment (all P < 0.050). And its improvement in itching scores (P7th < 0.001, P30th = 0.039, and P60th = 0.031) and TBUT (P7th = 0.009, P30th = 0.003, and P60th = 0.005) was more significant than the control group at all follow-up periods. The tear total IgE, interleukin (IL)-5, IL-6, periostin, eotaxin-3, and MMP-9 levels significantly decreased in the CsA group at day 60 after treatment (all P < 0.050). And the changed values in tear total IgE were positively correlated with the change in itching scores.

CONCLUSIONS

0.05% CsA eye drops (II) monotherapy can rapidly improve the symptoms and signs, especially in ocular itching and TBUT, in patients with ACDE. And its efficacy is superior to 0.1% olopatadine combined with artificial tears. Moreover, CsA downregulates the expression levels of tear inflammatory cytokines, including tear total IgE, IL-5, IL-6, periostin, eotaxin-3, and MMP-9. Among that, the reduction in tear total IgE levels may reflect the improvement of ocular itching.

Time-series analysis of the association between air pollution exposure and outpatient visits for dry eye disease: a case study in Zhengzhou, China

Background

Dry eye disease (DED) is a prevalent ocular surface disease that significantly impacts patients' quality of life. The association between air pollution and the risk of dry eye disease remains uncertain.

Methods

Data on outdoor air pollutants, meteorological information, and outpatient visits for DED were collected from July 1, 2014, to December 31, 2019. The relationship between ambient air pollutants and DED outpatient visits was analyzed using a generalized additive model with a Poisson distribution.

Results

Among the 5,204 DED patients included in the study, 63.76% were female and 36.24% were male. The single-pollutant model revealed a significant association between a 10 μg/m3 increase in concentrations of fine-particulate matter with a median aerometric diameter of less than 10 μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) and outpatient visits for DED. Fine-particulate matter with a median aerometric diameter of less than 2.5 μm (PM2.5) showed a significant association with DED outpatient visits in males and the 19-59 years age group. The strongest associations between air pollutants and outpatient visits were observed in male patients and during the cold season.

Conclusion

The noteworthy correlation between air pollutants and DED outpatient visits can offer evidence for policy makers and underscore the significance of reinforcing environmental protection.

Correlation between gout and dry eye disease

BACKGROUND

Gout is a common form of inflammatory arthritis that can cause a number of serious complications. Complications are common in patients with gout and complicate their management and disease outcome. The recent literature has reported that an increasing number of gout patients are presenting with dry eye symptoms. However, until now, the link between gout and dry eye disease has not been clearly defined. (It is unclear whether the two conditions simply co-exist, whether there are common risk factors, or whether dry eye disease is a complication of gout.) METHODS: A thorough literature search was conducted in the PubMed database to summarize the most recent information on the correlation between gout and dry eye disease and to explore the potential relationship between the pathogenesis of the two. (Objective: Therefore, in this paper, we review the recent literature on the correlation between gout and dry eye disease and explore the potential association between the pathogenesis of both.) RESULTS: Studies in the last five years have shown a correlation between gout and dry eye, i.e., gout is associated with an increased risk of dry eye. The NLRP3-IL-1β signaling pathway may be a potential mechanism for the combination of gout and dry eye disease; factors such as high blood uric acid and xanthine oxidase activation in gout patients may aggravate the development of dry eye disease; reducing the use of visual display terminals; reducing or abstaining from alcohol consumption; and moderate coffee intake may effectively prevent gout and dry eye disease.

CONCLUSIONS

It is an undisputed fact that many gout patients present with dry eye manifestations that seriously affect the quality of life of gout patients, and early detection and treatment of dry eye in gout patients are crucial.

The Inflammatory and Cytological Effect of Repeated Povidone-Iodine Application in Patients Receiving Intravitreal Injections

OBJECTIVE

To investigate the effect of repeated povidone-iodine (PVI) application on the ocular surface parameters of patients who received intravitreal injections.

MATERIALS AND METHODS

In this prospective study, 52 eyes of 52 patients with age-related macular degeneration who underwent unilateral intravitreal injection at least three times in the last 1 year (intravitreal injection [IVI] group), 52 fellow eyes with no previous intravitreal injection (NIVI group), and 51 eyes of 51 healthy subjects (control) were included. Tear break-up time (TBUT), the Schirmer test, the Oxford staining score, the Ocular Surface Disease Index questionnaire, conjunctival impression cytology, and tear inflammatory cytokine levels (interleukin [IL]-1β and IL-6) were analyzed in all participants.

RESULTS

The IVI group had lower TBUT and higher Oxford staining score than the NIVI and control groups ( P <0.05). No significant difference was found between the groups in the Schirmer test ( P =0.161). Conjunctival impression cytology analysis revealed that the IVI group had a significantly lower goblet cell count and significantly higher Nelson staging result than the NIVI and control groups ( P <0.05). As a result of tear cytokine analysis, although IVI and NIVI groups had higher IL-1β and IL-6 levels than the control group ( P <0.05), there was no difference between NIVI and IVI groups ( P ≥0.05).

CONCLUSIONS

Repeated PVI application caused cytotoxic injury to the ocular surface, resulting in goblet cell loss and squamous metaplasia of epithelial cells. As a result, the stability of the tear film layer was found to be impaired and ocular surface-related symptoms developed in patients.

Complement activation products in tears of dry eye and meibomian gland dysfunction

Sixty-seven patients (38 woman; median age, 69 years) were enrolled to assess complement activation products (CAPs) in tear fluid with/without dry eye (DE) and with/without meibomian gland dysfunction (MGD). Patients were divided into four groups based on the presence/absence of DE and MGD: group DM had both DE and MGD, group DN had DE without MGD, group NM had MGD without DE, and group NN had neither DE nor MGD. The levels of C3a and C5a in the collected tears were analyzed using a cytometric bead array. The C3a concentrations in the DM, DN, NM, and NN groups were 2326 pg/ml, 1411 pg/ml, 1821 pg/ml, and 978 pg/ml, respectively. The C5a concentrations in the DM, DN, NM, and NN groups were 24.7 pg/ml, 15.3 pg/ml, 24.1 pg/ml, and 12.9 pg/ml, respectively. The concentrations of C3a and C5a in the DM and NM groups were significantly higher than in the NN group (P < 0.05 for both comparisons). The CAPs in the tear fluid in MGD and DE increased. Local dysregulation of the innate immune system can be associated with the development of MGD and DE in elderly patients.

Oxidative stress in the eye and its role in the pathophysiology of ocular diseases

Oxidative stress occurs through an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense mechanisms of cells. The eye is particularly exposed to oxidative stress because of its permanent exposure to light and due to several structures having high metabolic activities. The anterior part of the eye is highly exposed to ultraviolet (UV) radiation and possesses a complex antioxidant defense system to protect the retina from UV radiation. The posterior part of the eye exhibits high metabolic rates and oxygen consumption leading subsequently to a high production rate of ROS. Furthermore, inflammation, aging, genetic factors, and environmental pollution, are all elements promoting ROS generation and impairing antioxidant defense mechanisms and thereby representing risk factors leading to oxidative stress. An abnormal redox status was shown to be involved in the pathophysiology of various ocular diseases in the anterior and posterior segment of the eye. In this review, we aim to summarize the mechanisms of oxidative stress in ocular diseases to provide an updated understanding on the pathogenesis of common diseases affecting the ocular surface, the lens, the retina, and the optic nerve. Moreover, we discuss potential therapeutic approaches aimed at reducing oxidative stress in this context.

Detection of pro-inflammatory cytokines in healthy canine tears using Canine Cytokine SpikeMix™ mass spectrometry via multiple reaction monitoring

PURPOSE

To evaluate the efficacy of the Canine Cytokine SpikeMix™ and MRM-MS for detecting pro-inflammatory cytokines in canine tears from healthy research Beagles.

METHODS

A complete ophthalmic examination was performed on 15 healthy research Beagles to verify no ophthalmic diseases. Tears were collected OU by placing a Weck-Cel® cellulose spear in the ventral conjunctival fornix for 1 min. The Weck-Cel® spear was placed in a 2.0 mL tube with a centrifuge filter forcing tears to flow through the filter into the bottom of the tube. The tears were analyzed using the Canine Cytokine SpikeMix™ and MRM-MS. Descriptive data from this study was reported as the normalized total peak area (nTPA) and median (range) using data imported from the online MRM-MS Skyline program.

RESULTS

The level of 16 pro-inflammatory cytokines was successfully detected in all 15 dogs. The four cytokines with the highest median amounts in the samples were IL-2 = 0.1243 (0.019-6.7289), IL-6 = 0.964 (0.0036-16.9365), TNFα = 0.1644 (0.0096-0.7138), and CSF-2 = 0.4022 (0.1475-2.6208).

CONCLUSIONS

This study revealed that 16 pro-inflammatory cytokines in canine tears from healthy dogs can be detected with Canine Cytokine SpikeMix™ and MRM-MS.

Optical Coherence Tomography Angiography for Evaluation of Conjunctival Vessels in Dry Eyes

Objective

This study aimed to evaluate conjunctival vessels in patients with dry eye disease (DED) using optical coherence tomography angiography (OCTA).

Methods

This was a cross-sectional, observational clinical study. Twenty-three eyes of 18 patients with DED and 28 eyes of 23 healthy controls were included for examination in this study. The evaluation included the application of an Ocular Surface Disease Index Questionnaire, Schirmer Basic Secretion Test, and anterior OCTA targeting the temporal conjunctiva. AngioTool software was used to quantify the total vessel length and vessel density in the 3 × 3 mm temporal region of interest.

Results

Blood vessel density measurements were compared across the OCTA systems. The total vessel length within the conjunctiva of the DED group (4799.34 ± 834.36) exceeded that of the control eye (3864.89 ± 1455.70) group (P < 0.05). However, the difference in vessel density between the two groups was not statistically significant.

Conclusion

Measurement and analysis of conjunctival blood vessels using OCTA exhibited robust repeatability. In dry eyes, the total number of conjunctival blood vessels increased in accordance with disease severity. Hypoxia of conjunctival tissue may be an important cause of dry eye disease.

Greater adherence to a mediterranean diet is associated with lower C-reactive protein (CRP) levels, but not to lower odds of having dry eye disease

PURPOSE

To investigate the hypothesis that a Mediterranean diet is associated with a lower risk of having dry eye disease (DED) in the general population.

METHODS

DED was assessed using the Women's Health Study (WHS) dry eye questionnaire in 58,993 participants from the Dutch Lifelines Cohort with complete available dietary data (20-94 years, 60% female). Level of adherence to a traditional Mediterranean diet was assessed using the modified Mediterranean Diet Score (mMDS). High-sensitivity C-reactive Protein (hsCRP) was included as a marker of whole-body inflammation. Logistic regressions were used to examine the relationship between WHS-defined DED and mMDS, corrected for age, sex, BMI, education, income, and 48 potentially confounding comorbidities. The association between mMDS and hsCRP, and hsCRP and DED, was further explored in separate regressions.

RESULTS

Of all participants, 9.1% had DED. In contrast to the hypothesis, higher mMDS levels were associated with greater odds of DED, corrected for demographics, smoking status, BMI, and comorbidities (OR 1.034, 95%CI: 1.015 to 1.055, P = 0.001). Moreover, there was a highly significant relationship between increasing mMDS and lower circulating hsCRP levels; however, there was no significant relationship between hsCRP and DED.

CONCLUSIONS

Stronger adherence to a Mediterranean diet does not appear to be associated with lower odds of having DED in the general population. Furthermore, there was no association between hsCRP and DED in this study. However, the previously described link between a Mediterranean diet and lower hsCRP was confirmed in this large population-based study.

Ocular instillation of conditioned medium from mesenchymal stem cells is effective for dry eye syndrome by improving corneal barrier function

Dry eye syndrome (DES) is a chronic ocular disease that induces epithelial damage to the cornea by decreasing tear production and quality. Adequate treatment options have not been established for severe DES such as Sjogren's syndrome due to complicated pathological conditions. To solve this problem, we focused on the conditioned medium of human adipose-derived mesenchymal stem cells (hAdMSC-CM), which have multiple therapeutic properties. Here, we showed that hAdMSC-CM suppressed Benzalkonium Chloride (BAC)-induced cytotoxicity and inflammation in human corneal epithelial cells (hCECs). In addition, hAdMSC-CM increased the expression level and regulated the localisation of barrier function-related components, and improved the BAC-induced barrier dysfunction in hCECs. RNA-seq analysis and pharmacological inhibition experiments revealed that the effects of hAdMSC-CM were associated with the TGFβ and JAK-STAT signalling pathways. Moreover, in DES model rats with exorbital and intraorbital lacrimal gland excision, ocular instillation of hAdMSC-CM suppressed corneal epithelial damage by improving barrier dysfunction of the cornea. Thus, we demonstrated that hAdMSC-CM has multiple therapeutic properties associated with TGFβ and JAK-STAT signalling pathways, and ocular instillation of hAdMSC-CM may serve as an innovative therapeutic agent for DES by improving corneal barrier function.

Tear Cytokine Levels in Sicca Syndrome-Related Dry Eye: A Meta-Analysis

Sjogren's syndrome (SS) is an autoimmune disease that affects exocrine glands, mainly salivary and lacrimal glands. Several studies have investigated cytokine profiles in tears in order to understand the pathogenesis of SS and find additional diagnostic markers. This systematic review and meta-analysis aimed to analyze cytokines in tears of SS patients. A systematic literature search of the Cochrane, Medline via PubMed, Scopus, and Web of Science databases was conducted using key terms related to "Sjögren's syndrome" and "tears" combined with "biomarker", "cytokines", "interleukin", and "chemokines", following PRISMA guidelines. Article selection was subjected to certain eligibility criteria. A total of 17 articles (from 1998 and 2022) were selected for the quantitative and qualitative analysis. When compared to controls, concentrations of IFN-γ, TNF-α, IL-1α, IL-1 Ra, IL-4, IL-6, IL-8, IL-10, IL-17, IL-21 and IL-22 were consistently higher; however, IL-23 was significantly lower in patients with SS compared to the controls. Tear levels of some cytokines were significantly elevated among SS groups compared to control groups. Therefore, these cytokines could be potential biomarkers of SS. However, standardization of sample collection and analytical methods is necessary in order to translate these findings into clinical practice.

Impact of Plasma Rich in Growth Factors (PRGF) Eye Drops on Ocular Redness and Symptomatology in Patients with Dry Eye Disease

Background and Objectives: Dry eye disease (DED) is a common and very symptomatic pathology that affects normal daily activity. The aim of the study was to evaluate the efficacy of plasma rich in growth factors (PRGF) added to one routine treatment protocol for DED (artificial tears substitutes, lid hygiene, and anti-inflammatory therapy). Materials and Methods: Patients were divided into two groups of treatment: standard treatment group (n = 43 eyes) and PRGF group (n = 59). Patients' symptomatology (inferred from OSDI and SANDE questionnaires), ocular inflammation, tear stability, and ocular surface damage were analyzed at baseline and after 3 months of treatment. Results: OSDI test scores were significantly lower in both groups (p < 0.001). SANDE frequency test scores also improved statistically, with differences between groups (p = 0.0089 SANDE frequency and p < 0.0119 SANDE severity). There was a greater reduction in ocular redness (ocular inflammation) in the PRGF group (p < 0.0001) and fluorescein tear break-up time was significantly improved in the PRGF group (p = 0.0006). No significant changes were found in terms of ocular surface damage. No adverse events were obtained in either group. Conclusions: The addition of PRGF to the standard treatment of DED, according to the results obtained, proved to be safe and produced an improvement in ocular symptomatology and signs of inflammation, particularly in moderate and severe cases, when compared to standard treatment.

Effectiveness of Topical Cyclosporin-A 0.1% Compared to Combined Topical Cyclosporin-A 0.1% with Topical Sodium Hyaluronate on Interleukin-6 Levels in the Tears of Patients with Dry Eye Disease

Introduction: Pro-inflammatory cytokines are important contributors to dry eye disease (DED). The cytokine interleukin (IL)-6 has become a therapeutic target in several DED drug studies. This randomized controlled trial aimed to determine the effectiveness of topical cyclosporin-A 0.1% compared to the combination of topical cyclosporin-A 0.1% and sodium hyaluronate in reducing tear IL-6 levels in DED patients. Methods: The participants were 20 patients, each with two eyes, who had moderate-to-severe DED. Before and after treatment, the clinical degree of DED was examined in each group, using ocular surface disease index (OSDI) scores, tear break-up time (TBUT), fluorescent tests, and Schirmer I tests. In addition, tear samples were taken to examine IL-6 levels through the ELISA method. The results were analyzed using the t-test, Wilcoxon test, and Mann–Whitney test. The correlation between tear IL-6 levels and the severity of DED was analyzed using the Spearman correlation test. Results: The study showed a significantly lower tear IL-6 level, OSDI score, and degree of ocular staining after either topical cyclosporin-A 0.1% or a combination of topical cyclosporin-A 0.1% and sodium hyaluronate (all values p < 0.05). Conclusions: The combination therapy was superior in reducing tear IL-6 levels. In addition, a correlation existed between tear IL-6 levels and the severity of DED based on the TBUT, although it was weak and not statistically significant.

Polymorphisms in Lymphotoxin-Alpha as the "Missing Link" in Prognosticating Favourable Response to Omega-3 Supplementation for Dry Eye Disease: A Narrative Review

Elements of inflammation are found in almost all chronic ocular surface disease, such as dry eye disease. The chronicity of such inflammatory disease speaks to the dysregulation of innate and adaptive immunity. There has been a rising interest in omega-3 fatty acids to attenuate inflammation. While many cell-based (in vitro) studies verify the anti-inflammatory effects of omega-3, different human trials report discordant outcomes after supplementation. This may be due to underlying inter-individual differences in inflammatory cytokine metabolism (such as tumor necrosis factor alpha (TNF-α)), in which genetic differences might play a role, such as polymorphisms in the lymphotoxin alpha (LT-α) gene. Inherent TNF-α production affects omega-3 response and is also associated with LT-α genotype. Therefore, LT-α genotype might predict omega-3 response. Using the NIH dbSNP, we analyzed the relative frequency of LT-α polymorphisms among various ethnicities, each weighted by the genotype's probability of positive response. While the probability of response for unknown LT-α genotypes are 50%, there is greater distinction in response rates between various genotypes. Hence, there is value in genetic testing to prognosticate an individual's response to omega-3.

Impact of Tumor Necrosis Factor Receptor 1 (TNFR1) Polymorphism on Dry Eye Disease

The goal of the study was to examine whether a genetic polymorphism in tumor necrosis factor receptor 1 (TNFR1) gene impacted the dry eye disease (DED) phenotype and response to anti-inflammatory therapy. The prospective study included 328 individuals with various dry eye (DE) symptoms and signs recruited from the Miami Veterans Hospital eye clinic between October 2013 and October 2017. The population underwent genetic profiling for a polymorphism within the TNFR1 gene (rs1800693 [TT, TC, CC]). The study examined the genotype distribution and relationships between the genotype, phenotype, and response to anti-inflammatory therapy. The mean age of the population was 61.7 ± 9.8 years. Here, 92% self-identified as male, 44% as White, and 21% as Hispanic; 13% (n = 42) of individuals had a CC genotype. DED symptoms and signs were similar across the three genotype groups. Thirty individuals (four with CC) were subsequently treated with an anti-inflammatory agent. There was a non-significant trend for individuals with CC genotype to have a partial or complete symptomatic response to treatment compared with the other two groups (100% for CC vs. 40% for TT and 36.4% for TC, p = 0.22). In conclusion, the presence of homozygosity of minor allele C (CC genotype) in a single nucleotide polymorphism (SNP) within TNFR1 was noted in a minority of individuals with various aspects of DED, but did not impact the DED phenotype. Our findings suggest that the current phenotyping strategies for DED are insufficient to identify underlying disease contributors, including potential genetic contributors.

Pathophysiology of Corneal Endothelial Cell Loss in Dry Eye Disease and Other Inflammatory Ocular Disorders

PURPOSE

Dry eye disease (DED) and other inflammatory ocular disorders have been reported to be associated with decreased corneal endothelial cell density (CECD), however the mechanism of underlying endothelial cell loss remains unknown.

METHODS

We conducted a comprehensive literature search of English-written publications on dry eye disease, corneal endothelial cell loss, Sjögren's syndrome, and Graft Vs Host Disease (GVHD), to review the effects of DED and other inflammatory ocular surface conditions on CECD.

RESULTS

A total of 78 studies were included in our study. Loss of corneal neurotrophic support, cytotoxic stress, and a heightened immune response, all of which may occur secondarily to a common causative agent such as inflammation, are major contributors to reduced CECD.

CONCLUSION

More studies are needed to determine how the interrelated pathways of altered corneal nerve function and upregulated expression of inflammatory activity influence corneal endothelial cell loss.

Therapeutic Effects of Acer palmatum Thumb. Leaf Extract (KIOM-2015E) on Benzalkonium Chloride-Induced Dry Eye in a Mouse Model

We determined the effects of two extracts from Acer palmatum Thumb. leaves (hot water extract KIOM-2015EW and 25% ethanol extract KIOM-2015EE) in a benzalkonium chloride (BAC)-induced dry eye mouse model. Dry eye was induced by 0.2% BAC for 2 weeks, followed by treatment three times (eye drop) or once (oral administration) daily with KIOM-2015E for 2 weeks. Treatment with both KIOM-2015EE and KIOM-2015EW resulted in a marked increase in tear volume production for the 4 days of treatment. The Lissamine Green staining score, TUNEL-positive cells, and inflammatory index were significantly decreased after 2 weeks. Topical KIOM-2015EE administration exhibited a greater improvement in decreasing the ocular surface staining scores, inflammation, dead cells, and increasing tear production in a dose-dependent manner compared with the other groups. Furthermore, KIOM-2015E significantly reduced the phosphorylation of NF-κB, which was activated in the BAC-treated cornea. Topical administration was much more effective than oral administration for KIOM-2015E and KIOM-2015EE was more effective than KIOM-2015EW. Application of KIOM-2015E resulted in clinical improvement, inhibited the inflammatory response, and alleviated signs of dry eye. These results indicate that KIOM-2015E has potential as a therapeutic agent for the clinical treatment of dry eye.

Evidence of air pollution-related ocular signs and altered inflammatory cytokine profile of the ocular surface in Beijing

We evaluated how different degrees of air pollution affect the ocular surface of a cohort of human subjects in Beijing by correlating in-patient test outcomes with tear cytokines. A cross-sectional study involving 221 volunteers was carried out in different districts of Beijing. Air pollution indices were recorded for 7 d (including the visit day). The indices recorded were the air quality index (AQI), which is a dimensionless measure that quantitatively describes the state of air quality, concentrations of particulate matter smaller than 2.5 μm (PM2.5) and 10 μm (PM10), sulfur dioxide (SO₂), ozone (O₃), and nitrogen dioxide (NO₂). The Ocular Symptom Disease Index (OSDI) questionnaire provided. Subsequently, subjects underwent slit-lamp examination, which included meibomian gland examination, conjunctival congestion score, conjunctivochalasis grade, tear meniscus height (TMH), tear breakup time (TBUT), corneal fluorescein staining (CFS), Schirmer I test, and conjunctival impression cytology. The concentrations of vascular endothelial growth factor (VEGF), interleukins (IL)-1β, IL-6 and IL-8 in tears were measured by microsphere-based immunoassay analysis. According to the value of the AQI, participants are divided into a slightly polluted (SP) group (n = 103) which the AQI value is less than or equal to 100 and a heavily polluted (HP) group (n = 118) whose AQI value is more than 100. Air pollution is related to ocular discomfort based on tear cytokine concentrations. PM2.5, PM10 and NO₂ were positively correlated with OSDI, MG expressibility, meibum score, meiboscore, conjunctival congestion score, Schirmer I test value, TMH, goblet-cell density, concentrations of IL-6, and VEGF were negatively correlated with TBUT. PM2.5 and PM10 appear to be the major risk factors to the ocular surface, with NO₂ being another important risk factor based on this study. The symptoms and signs of eye discomfort in the SP group were significantly less severe than those in the HP group, and tear cytokine concentrations (IL-6 and VEGF) were lower. Air pollution degrees were significantly correlated with tear cytokine concentrations, indicating an alteration of cytokine balance at the ocular surface under different degrees of air pollution.

Role of ocular surface neurobiology in neuronal-mediated inflammation in dry eye disease

Inflammation is the consequence of dry eye disease regardless of its etiology. Several injurious or harmless processes to the ocular surface neurons promote ocular surface neurogenic inflammation, leading to the vicious cycle of dry eye disease. These processes include the regular release of neuromediators during the conduction of ocular surface sensations, hyperosmolarity-induced ocular surface neuronal damage, neuro-regenerative activities, and neuronal-mediated dendritic cell activities. Neurogenic inflammation appears to be the main culprit, instigating the self-perpetuating inflammation observed in patients with dry eye disease.

Oxytocin and secretin receptors - implications for dry eye syndrome and ocular pain

Dry eye syndrome, a form of ocular surface inflammation, and chronic ocular pain are common conditions impacting activities of daily living and quality of life. Oxytocin and secretin are peptide hormones that have been shown to synergistically reduce inflammation in various tissues and attenuate the pain response at both the neuron and brain level. The oxytocin receptor (OXTR) and secretin receptor (SCTR) have been found in a wide variety of tissues and organs, including the eye. We reviewed the current literature of in vitro experiments, animal models, and human studies that examine the anti-inflammatory and anti-nociceptive roles of oxytocin and secretin. This review provides an overview of the evidence supporting oxytocin and secretin as the basis for novel treatments of dry eye and ocular pain syndromes.

Ocular Surface Inflammatory Disorders (OSID): A Collective of Systemic Etiologies Which Cause or Amplify Dry Eye Syndrome

The ocular surface inflammatory disorders (OSID) are caused by systemic disorders that conduct a persistent inflammatory reaction in the ocular adnexal connective tissues, such as the conjunctiva, lacrimal gland (LG) and meibomian glands (MGs), which cause an inflammatory dry eye. The etiologies of OSID are a subset of systemic pathologies such as graft versus host disease, Sjögren’s syndrome, allergies, cicatrizing conjunctivitis, and more. These cause a purely inflammatory dry eye syndrome as a consequence of the persistent surrounding inflammation in the adnexal tissues, which is distinct from the age-related dry eye disease. A limitation toward management of these conditions is the lack of available biomarkers that can detect presence of inflammation and quantify damage on the conjunctiva and LG, even though these are considered to be drivers of the inflammatory milieu. The OSID and dry eye syndrome are caused by different immune cells which are not exclusively limited to T cell lymphocytes, but rather derive from an orchestrated multicellular immunologic response. Recognition of this syndrome is crucial to direct research in a direction that clarifies the potential role of inflammation and its associated immune phenotype on the conjunctiva and adnexal ocular tissues in OSID and dry eye syndrome. On this paper, we review the basic and clinical research evidence for the existence of OSID with focus on the different immune cells involved, the target tissues and potential consequences and OSIDs diagnostic and therapeutic implications.

Tear and ocular surface disease biomarkers: A diagnostic and clinical perspective for ocular allergies and dry eye disease

Validated biomarkers to be used as biological tools for managing ocular surface diseases (OSDs) are still an unmet need in daily clinical practice. Many studies have contributed to the already extensive list of candidate biomarkers for these disorders. Dry eye (DE) and ocular allergy (OA) are complex and multifactorial diseases, often coexisting and with overlapping symptoms. The purpose of this review is to present a comprehensive updated revision of the most relevant biomarkers of DE and OA, with an emphasis on quantitative analyses and correlations with clinical parameter data. Analysis of biomarkers common for these pathologies has highlighted an important physiological process. Namely, the interleukin proteins (IL-1α, IL-1β and IL-17), tumour necrotic factor (TNFα) and interferon gamma (IFNγ; Th1-Th7 pathway) and IL-4, IL-5 and IL-13 (Th2 pathway) seem to represent similar inflammatory mechanisms. Moreover, changes in the levels of mucins (MUC1, MUC2, MUC4, MUC5 and MUC16) are common alterations in the tear film mucous layer. We also examine the current state of medical devices and the main limitations to their use in clinical practice. Translational research in biomarkers for clinical practice depends on a feasible transition from the laboratory to the point-of-care. This requires large-scale, coordinated clinical validation campaigns to select the biomarkers with the highest specificity and sensitivity and significant correlation with clinical parameters. Moreover, technical limitations of multiplexed quantitation systems must be overcome to detect and measure the levels of several biomarkers in very small samples. To ensure the future of biomarker research, significant progress is necessary in a number of fields. There is an urgent need for global unification of clinical classification and diagnostics criteria. Widespread integration of proteomic and transcriptomic data is paramount for performing meaningful analyses using appropriate bioinformatics tools and artificial intelligence systems.

Cardiovascular Involvement in Sjögren’s Syndrome

Sjögren Syndrome (SS) seems to be associated with a greater “overall risk” of cardiovascular (CV) and cerebrovascular events. Although not conventionally considered a feature of the disease, CV events represent a major burden in SS patients. CV risk is the consequence of a complex combination of multiple factors, including traditional risk factors and disease-related mechanisms. A complex relationships between disease-related features, endothelial dysfunction and traditional risk factor has been suggested. Several drugs are available for treating the systemic manifestations of SS, however they have shown positive effects on different outcomes of the disease, but until today the data on the role of these drugs on CV events are scarse. Given these data, the aim of this review was to evaluate the risk of CV risk in primary SS and the effect of the drugs on this manifestation.

IGFBP-3 Regulates Mitochondrial Hyperfusion and Metabolic Activity in Ocular Surface Epithelia during Hyperosmolar Stress

In the eye, hyperosmolarity of the precorneal tear film triggers inflammation and the development of dry eye disease (DED), a highly prevalent condition that causes depression and disability in severe forms. A member of the insulin-like growth factor (IGF) family, the IGF binding protein-3 (IGFBP-3), is a pleiotropic protein with known roles in growth downregulation and survival. IGFBP-3 exerts these effects by blocking IGF-1 activation of the type 1 IGF-receptor (IGF-1R). Here, we examined a new IGF-independent role for IGFBP-3 in the regulation of mitochondrial and metabolic activity in ocular surface epithelial cells subject to hyperosmolar stress and in a mouse model of DED. We found that hyperosmolar stress decreased IGFBP-3 expression in vitro and in vivo. Treatment with exogenous IGFBP-3 induced an early, transient shift in IGF-1R to mitochondria, followed by IGFBP-3 nuclear accumulation. IGFBP-3 nuclear accumulation increased protein translation, blocked the hyperosmolar-mediated decrease in oxidative phosphorylation through the induction of mitochondrial hyperfusion, and restored corneal health in vivo. These data indicate that IGFBP-3 acts a stress response protein in ocular surface epithelia subject to hyperosmolar stress. These findings may lead to the development of first-in-class therapeutics to treat eye diseases with underlying mitochondrial dysfunction.

GlicoPro, Novel Standardized and Sterile Snail Mucus Extract for Multi-Modulative Ocular Formulations: New Perspective in Dry Eye Disease Management

This study aimed to evaluate the mucoadhesive and regenerative properties of a novel lubricating multimolecular ophthalmic solution (GlicoPro^®) extracted from snail mucus and its potential anti-inflammatory and analgesic role in the management of dry eye disease (DED). GlicoPro bio-adhesive efficacy was assessed using a lectin-based assay, and its regenerative properties were studied in a human corneal epithelial cell line. In vitro DED was induced in human corneal tissues; the histology and mRNA expression of selected genes of inflammatory and corneal damage biomarkers were analyzed in DED tissues treated with GlicoPro. A higher percentage of bio-adhesivity was observed in corneal cells treated with GlicoPro than with sodium hyaluronate-based compounds. In the scratch test GlicoPro improved in vitro corneal wound healing. Histo-morphological analysis revealed restoration of cellular organization of the corneal epithelium, microvilli, and mucin network in DED corneal tissues treated with GlicoPro. A significant reduction in inflammatory and ocular damage biomarkers was observed. High-performance liquid chromatography-mass spectrometry analysis identified an endogenous opioid, opiorphin, in the peptide fraction of GlicoPro. In conclusion, GlicoPro induced regeneration and bio-adhesivity in corneal cells; moreover, considering its anti-inflammatory and analgesic properties, this novel ophthalmic lubricating solution may be an innovative approach for the management of DED.

Mass spectrometry analysis of human tear fluid biomarkers specific for ocular and systemic diseases in the context of 3P medicine

Over the last two decades, a large number of non-communicable/chronic disorders reached an epidemic level on a global scale such as diabetes mellitus type 2, cardio-vascular disease, several types of malignancies, neurological and eye pathologies-all exerted system's enormous socio-economic burden to primary, secondary, and tertiary healthcare. The paradigm change from reactive to predictive, preventive, and personalized medicine (3PM/PPPM) has been declared as an essential transformation of the overall healthcare approach to benefit the patient and society at large. To this end, specific biomarker panels are instrumental for a cost-effective predictive approach of individualized prevention and treatments tailored to the person. The source of biomarkers is crucial for specificity and reliability of diagnostic tests and treatment targets. Furthermore, any diagnostic approach preferentially should be noninvasive to increase availability of the biomaterial, and to decrease risks of potential complications as well as concomitant costs. These requirements are clearly fulfilled by tear fluid, which represents a precious source of biomarker panels. The well-justified principle of a "sick eye in a sick body" makes comprehensive tear fluid biomarker profiling highly relevant not only for diagnostics of eye pathologies but also for prediction, prognosis, and treatment monitoring of systemic diseases. One prominent example is the Sicca syndrome linked to a cascade of severe complications that include dry eye, neurologic, and oncologic diseases. In this review, protein profiles in tear fluid are highlighted and corresponding biomarkers are exemplified for several relevant pathologies, including dry eye disease, diabetic retinopathy, cancers, and neurological disorders. Corresponding analytical approaches such as sample pre-processing, differential proteomics, electrophoretic techniques, high-performance liquid chromatography (HPLC), enzyme-linked immuno-sorbent assay (ELISA), microarrays, and mass spectrometry (MS) methodology are detailed. Consequently, we proposed the overall strategies based on the tear fluid biomarkers application for 3P medicine practice. In the context of 3P medicine, tear fluid analytical pathways are considered to predict disease development, to target preventive measures, and to create treatment algorithms tailored to individual patient profiles.

Lactoferrin Ameliorates Dry Eye Disease Potentially through Enhancement of Short-Chain Fatty Acid Production by Gut Microbiota in Mice

Lactoferrin is a glycoprotein found at high concentrations within exocrine secretions, including tears. Low levels of lactoferrin have been implicated in the loss of tear secretion and ageing. Furthermore, lactoferrin possesses a range of functionalities, including anti-inflammatory properties and the ability to modulate the gut microbiota. Expanding evidence demonstrates a crucial role of the gut microbiota in immune regulation and development. The specific composition of bacterial species of the gut has a profound influence on local and systemic inflammation, leading to a protective capacity against a number of inflammatory diseases, potentially by the induction of regulatory immune cells. In this study, we demonstrated that oral administration of lactoferrin maintains tear secretion in a restraint and desiccating stress induced mouse model of dry eye disease. Furthermore, we revealed that lactoferrin induces the reduction of inflammatory cytokines, modulates gut microbiota, and induces short-chain fatty acid production. Whereas, the antibiotic vancomycin abrogates the effects of lactoferrin on dry eye disease and significantly reduces short-chain fatty acid concentrations. Therefore, this protective effect of LF against a mice model of DED may be explained by our observations of an altered gut microbiota and an enhanced production of immunomodulatory short-chain fatty acids.

Corneal neuromediator profiles following laser refractive surgery

Laser refractive surgery is one of the most commonly performed procedures worldwide. In laser refractive surgery, Femtosecond Laser in Situ Keratomileusis and Refractive Lenticule Extraction have emerged as promising alternatives to microkeratome Laser in Situ Keratomileusis and Photorefractive Keratectomy. Following laser refractive surgery, the corneal nerves, epithelial and stromal cells release neuromediators, including neurotrophins, neuropeptides and neurotransmitters. Notably, nerve growth factor, substance P, calcitonin gene-related peptide and various cytokines are important mediators of neurogenic inflammation and corneal nerve regeneration. Alterations in neuromediator profiles and ocular surface parameters following laser refractive surgery are attributed to the surgical techniques and the severity of tissue insult induced. In this review, we will discuss the (1) Functions of neuromediators and their physiological and clinical significance; (2) Changes in the neuromediators following various laser refractive surgeries; (3) Correlation between neuromediators, ocular surface health and corneal nerve status; and (4) Future directions, including the use of neuromediators as potential biomarkers for ocular surface health following laser refractive surgery, and as adjuncts to aid in corneal regeneration after laser refractive surgery.

Olive Pomace Phenolic Compounds and Extracts Can Inhibit Inflammatory- and Oxidative-Related Diseases of Human Ocular Surface Epithelium

Oxidative- and inflammatory-related ocular surface diseases have high prevalence and are an emerging issue in ophthalmology. Olive pomace (OP) is the olive oil's industry main by-product, and is potentially environmentally hazardous. Nevertheless, it contains phenolic compounds with important bioactivities, like oleuropein (OL) and hydroxytyrosol (HT). The antioxidant and anti-inflammatory effects of four OP extracts (CONV, OPT(1-3)), pure OL and HT, and mixtures thereof were screened on human corneal (HCE) and conjunctival epithelial (IM-ConjEpi) cells. CONV was conventionally extracted, while OPT(1-3) were produced by pressurized liquid extraction. Thanks to their improved activity, CONV and OPT3 (HT-enriched) were selected for dose-dependent studies. Cells were stimulated with tumor necrosis factor-α or ultraviolet-B radiation, measuring interleukin (IL)-1β, IL-6, IL-8, and IL-17A as well as interferon γ-induced protein [IP]-10 secretion or intracellular ROS production, respectively. On HCE, both extracts and HT inhibited the secretion of most measured ILs, demonstrating a strong anti-inflammatory effect; while in IM-ConjEpi, all samples decreased IP-10 secretion. Moreover, HT, OL, and both extracts showed strong dose-dependent antioxidant activity in both cell lines. Compared with CONV, OPT3 was active at lower concentrations, demonstrating that intensified extraction techniques are selective towards targeted biomarkers. Hence, a high-value application as potential ocular surface therapy was proposed for the OP valorization.

Differential Effect of Proinflammatory Cytokines on Corneal and Conjunctival Epithelial Cell Mucins and Glycocalyx

Purpose

Ocular surface mucins and glycocalyx are critical for providing ocular hydration as well lubrication and repelling pathogens or allergens. Elevated levels of tear proinflammatory cytokines in dry eye may have detrimental effect on mucins and glycocalyx. The present study tested the effect of proinflammatory cytokines IL-6, TNF-α, and IFN-γ on membrane-tethered mucins expression, glycocalyx, and viability of ocular surface epithelial cells.

Methods

Stratified cultures of human corneal and conjunctival epithelial cells were exposed to different concentrations of IL-6, TNF-α, and IFN-γ for 24 hours. The mucins gene and protein expressions were quantified by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). The glycocalyx was imaged using confocal microscopy after staining with Alexa 488-conjugated wheat germ agglutinin lectin. Apoptotic and necrotic cell death was quantified using flow cytometry.

Results

IL-6, TNF-α, and IFN-γ treatment resulted in a significant increase in mucins (MUC)1 and MUC4 gene and protein expression in human corneal epithelial cells but caused no significant changes in the levels of these mucins in conjunctival epithelial cells. Further, these cytokines decreased MUC16 expression in both corneal and conjunctival epithelial cells. Moreover, no notable change in glycocalyx or apoptotic cell death in corneal and conjunctival epithelial cells was noted with any of the tested cytokines, but IL-6 and TNF-α exposure increased necrotic cell death in corneal and conjunctival epithelial cells, respectively.

Conclusions

Our results demonstrate that proinflammatory cytokines have differential effects on human corneal and conjunctival epithelial cell mucins expression, but do not cause any damage to ocular surface epithelial cell glycocalyx.

Dexamethasone-Loaded Nanostructured Lipid Carriers for the Treatment of Dry Eye Disease

Dry eye disease (DED) or keratoconjunctivitis sicca is a chronic multifactorial disorder of the ocular surface caused by tear film dysfunction. Symptoms include dryness, irritation, discomfort and visual disturbance, and standard treatment includes the use of lubricants and topical steroids. Secondary inflammation plays a prominent role in the development and propagation of this debilitating condition. To address this we have investigated the pilot scale development of an innovative drug delivery system using a dexamethasone-encapsulated cholesterol-Labrafac™ lipophile nanostructured lipid carrier (NLC)-based ophthalmic formulation, which could be developed as an eye drop to treat DED and any associated acute exacerbations. After rapid screening of a range of laboratory scale pre-formulations, the chosen formulation was prepared at pilot scale with a particle size of 19.51 ± 0.5 nm, an encapsulation efficiency of 99.6 ± 0.5%, a PDI of 0.08, and an extended stability of 6 months at 4 °C. This potential ophthalmic formulation was observed to have high tolerability and internalization capacity for human corneal epithelial cells, with similar behavior demonstrated on ex vivo porcine cornea studies, suggesting suitable distribution on the ocular surface. Further, ELISA was used to study the impact of the pilot scale formulation on a range of inflammatory biomarkers. The most successful dexamethasone-loaded NLC showed a 5-fold reduction of TNF-α production over dexamethasone solution alone, with comparable results for MMP-9 and IL-6. The ease of formulation, scalability, performance and biomarker assays suggest that this NLC formulation could be a viable option for the topical treatment of DED.

Differential Diagnosis of Sjögren Versus Non-Sjögren Dry Eye Through Tear Film Biomarkers

PURPOSE

Systemic implications necessitate the identification of dry eye patients with Sjögren syndrome (SS). This study aims to explore the utility of tear MUC5AC and inflammatory cytokine levels in the differential diagnosis of SS-related dry eye.

METHODS

A prospective, observational, case-control study was conducted on 62 patients (those with a definitive diagnosis of SS dry eye, non-SS dry eye, and age-matched healthy controls with no dry eye). Clinical evaluations included the following tests in the order listed here: noninvasive tear break-up time, osmolarity, tear sampling, Schirmer test without anesthesia, and ocular surface staining (lissamine green for conjunctiva and fluorescein for cornea). Tear MUC5AC levels were assessed with enzyme-linked immunosorbent assay, and cytokines [interferon-gamma, tumor necrosis factor alpha, interleukin (IL)-6, IL-17a, IL-1β, IL-8, IL-10, and IL-12p70] were measured using a Luminex assay in a masked fashion.

RESULTS

The Bulbar conjunctival lissamine green staining score was significantly greater in patients or controls with SS versus non-SS dry eye. This greater conjunctival staining was associated with a reduction in tear MUC5AC (B = -17.8 ng/mL, 95% confidence interval = -31.8 to -3.9, P = 0.01). Among the tear cytokines, a significant association was found between IL-8 levels (hazard ratio [HR] = 1.002, 95% confidence interval = 1.000-1.003, P = 0.03) and SS diagnosis. When patients were stratified based on tear MUC5AC levels, significantly increased tear IL-8 levels were detected in patients with SS dry eye but not with non-SS dry eye, in comparison with healthy controls.

CONCLUSIONS

Tear levels of goblet cell-specific MUC5AC combined with IL-8 can potentially serve as a useful biomarker for differential diagnosis of SS dry eye from non-SS dry eye.

Characteristics and recurrence of pterygium in Saudi Arabia: a single center study with a long follow-up

Background

This study described the clinical features of patients with pterygium and analyzed the recurrence rate of conjunctival autografting alone, conjunctival autografting combined with intraoperative mitomycin C, and amniotic membrane grafting.

Methods

A retrospective cohort study of primary pterygium was conducted between January 2017 and February 2020. Factors associated with pterygium severity and recurrence were analyzed by univariate analysis and logistic regression models.

Results

The study included 292 patients with an average age of 53.3 ± 14.1 years, while the number of operated cases was 94. Pterygia involving the cornea were observed in 55 % of the cases. The overall rate of recurrence for the three procedures was 17 %. The average time of recurrence was 14.2 ± 11.9 months, with 37 % of the recurrences occurring after the first year. The only factor associated with a significant risk of recurrence was dry eye disease in both univariate (p = 0.021) and multivariate analysis (p = 0.026). The recurrence rates following conjunctival autografting with and without mitomycin C were 15.6 and 15.8 %, respectively. The recurrence rate following the amniotic membrane graft was  twofold (OR= 2.02)  (27 %) that following the conjunctival autograft (15.8 %).

Conclusions

The only factor associated with the recurrence of pterygium was dry eye disease. More than one-third of recurrences developed after the first year, which stresses the importance of a long follow-up. The recurrence rate in our study following conjunctival graft was slightly higher compared to the literature mainly due to differences in study areas, populations, and follow-up periods.

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.

Isorhamnetin Ameliorates Dry Eye Disease via CFTR Activation in Mice

Dry eye disease is one of the most common diseases, with increasing prevalence in many countries, but treatment options are limited. Cystic fibrosis transmembrane conductance regulator (CFTR) is a major ion channel that facilitates fluid secretion in ocular surface epithelium and is a potential target of therapeutic agent for the treatment of dry eye disease. In this study, we performed a cell-based, high-throughput screening for the identification of novel natural products that activate CFTR and restore the aqueous deficiency in dry eye. Screening of 1000 natural products revealed isorhamnetin, a flavonol aglycone, as a novel CFTR activator. Electrophysiological studies showed that isorhamnetin significantly increased CFTR chloride current, both wild type and ∆F508-CFTR. Isorhamnetin did not alter intracellular cAMP levels and the activity of other ion channels, including ANO1, ENaC, and hERG. Notably, application of isorhamnetin on mouse ocular surface induced CFTR activation and increased tear volume. In addition, isorhamnetin significantly reduced ocular surface damage and expression of interleukin (IL)-1β, IL-8, and tumor necrosis factor (TNF)-α in an experimental mouse model of dry eye. These data suggest that isorhamnetin may be used to treat dry eye disease.

Inflammatory proteins associated with contact lens-related dry eye

PURPOSE

To evaluate the levels and regulation of tear film inflammatory proteins in contact lens-related dry eye (CLDE).

METHODS

One hundred healthy, daily wear (non-overnight), experienced soft contact lens wearers were classified into normal (n = 50) and CLDE (n = 50) groups based on Contact Lens and Dry Eye Questionnaire scores, tear break-up times, and comfort (a two-hour difference between total and comfortable daily lens wear hours). Tear samples (up to 5 μL) were collected by capillary extraction from the inferior meniscus of each eye, and pooled tear samples (10 per group) were tested using a customized Quantibody array. Mann Whitney tests with the Benjamini-Hochberg procedure with a 5% false discovery rate were used to compare the normal and CLDE groups.

RESULTS

Relative to the normal group, the CLDE group showed a significantly increased tear concentration of several inflammatory mediators, including interleukin (IL)-7 (p = 0.001), IL-8 (p = 0.001), IL-13 (p = 0.001), IL-15 (p = 0.001), IL-12 p70 (p = 0.002), growth-related oncogene-alpha/ chemokine (CXC motif) ligand 1 (p = 0.003), granulocyte-colony stimulating factor (p = 0.005), IL-11 (p = 0.008), epidermal growth factor receptor (p = 0.01), IL-1 receptor antagonist (RA) (p = 0.013), macrophage colony-stimulating factor (p = 0.013), Eotaxin/CC motif chemokine ligand 11 (CCL11) (p = 0.016), and IL-2 (p = 0.016). The following cytokines were increased three-fold or more in the CLDE group: IL-13 (p = 0.001), Eotaxin/CCL11 (p = 0.016), and IL-1RA (p = 0.013).

CONCLUSIONS

Several inflammatory markers, including interleukins, were increased in tears of subjects with CLDE. These results support a growing body of evidence that suggests a potential role of inflammation in CLDE.

The Relationship between Corneal Nerve Morphology and Inflammatory Mediators and Neuropeptides in Healthy Individuals

SIGNIFICANCE

This study set out to explore the relationship between the ocular surface immune and nervous systems by exploring corneal nerve structure and the presence of inflammatory mediators and neuropeptides in the tear film.

PURPOSE

The purpose of this study was to determine the association between corneal nerve morphology and tear film inflammatory mediators and a neuropeptide in healthy individuals.

METHODS

Flush tears were collected from both eyes of 21 healthy participants aged 39.7 ± 9.9 years (10 females, 11 males) and analyzed for substance P, matrix metalloproteinase-9, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), tumor necrosis factor α, and interleukin 6. In vivo central corneal confocal microscopy was performed on the right eye, and eight images were captured. Variables measured were corneal nerve fiber length (CNFL), corneal nerve density (CNFD), corneal nerve branch density, fiber total branch density, corneal nerve fiber area, corneal nerve fiber width (CNFW), and corneal nerve fractal dimension (CNFrac). For each eye, the average across the images and the maximum and minimum values were determined for each variable. Pearson correlation analysis was performed to test for associations.

RESULTS

Substance P correlated with CNFrac (max) (r = -0.48, P = .03) and CNFW (min) (r = -0.52, P = .02). TIMP-1 correlated with CNFD (average) (r = -0.53, P = .03), CNFL (average) (r = -0.49, P = .05), CNFrac (max) (r = -0.49, P = .05), and CNFD (min) (r = -0.55, P = .02). Interleukin 6 correlated with CNFW (average) (r = -0.49, P = .05), the standard deviation of CNFL (r = -0.51, P = .04), CNFL (max) (r = -0.50, P = .04), CNFrac (max) (r = -0.50, P = .04), and CNFW (min) (r = -0.55, P = .02). Tumor necrosis factor α, matrix metalloproteinase-9, and its ratio with TIMP-1 did not correlate with any corneal nerve parameters.

CONCLUSIONS

Both inflammatory mediators and neuropeptides correlated with measures of corneal nerve morphology, supporting the link between the inflammatory and nervous systems.