Relationships between activated dendritic cells and dry eye symptoms and signs

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.

"Window of Opportunity" in Ocular Graft-Versus-Host Disease Treatment: Results of a Longitudinal Study and Case Reports

OBJECTIVE

To perform a longitudinal study for determining the development of ocular graft-versus-host disease (oGVHD) after allogeneic hematopoietic stem cell transplant (HSCT) and report cases that illustrate the "window of opportunity" concept in oGVHD treatment.

METHODS

Patients (n=61) were examined at prescheduled clinic visits before HSCT and three-month intervals after HSCT for 2 years. The presence or absence of oGVHD was determined using the international chronic oGVHD consensus group diagnostic criteria. Ocular surface washings (OSW) were obtained at each visit and analyzed for cytokine levels.

RESULTS

In the longitudinal study, 26.2% (n=16; progressed group) developed either probable (11.5%, n=7) or definite oGVHD (14.8%, n=9). In the progressed group, clinically significant changes in signs (corneal staining and Schirmer I test) and symptoms at the post-HSCT visit as compared with the pre-HSCT visit occurred at 9 months. Significant differences in clinical signs and symptoms (whether average post-HSCT values or changes in values over pre-HSCT levels) between the progressed and nonprogressed groups occurred at a 9-month visit or later. In the progressed group, 55.6% of eyes that had negative matrix metalloproteinase 9 (MMP-9) test at pre-HSCT turned MMP-9 positive at 3 to 6 months post-HSCT. In the progressed group, interleukin 8 levels in OSW were significantly increased at 6 months post-HSCT. In the case reports, the "window of opportunity" was detected by MMP-9 turning positive, early corneal staining, interleukin 8 increase in OSW, and peripheral corneal epithelial thinning, which resolved with treatment initiation.

CONCLUSIONS

A "window of opportunity" exists before patients developing symptomatic tear-deficient dry eye after HSCT for initiating treatment that may preempt oGVHD development; however, larger-scale longitudinal studies are needed for definitive recommendations.

Central corneal thickness in new cases of dry eyes: A case-control study

SIGNIFICANCE

Loss of homeostasis and chronic inflammation result in ocular surface damage in dry eyes, which is also associated with corneal thinning in established cases. Yet, the correlation between corneal thickness and new cases of dry eyes remains inadequately supported by evidence.

PURPOSE

This study aimed to compare the central corneal thickness of new cases of dry eyes to that of age- and gender-matched controls.

METHODS

A total of 45 dry eye patients were compared with 61 age- and gender-matched non-dry eye individuals. The Ocular Surface Disease Index (OSDI) questionnaire was used to evaluate symptoms, and the central corneal thickness was measured with a Nidek CEM-530 specular microscope. Patients were grouped based on disease severity (OSDI scores), and the clinical findings were compared between groups for slit-lamp examinations, Schirmer's I test, and tear film breakup time.

RESULTS

The median age of patients was 25.0 (interquartile range [IQR], 20.0 to 32.0) and 27.0 (IQR, 20.0 to 32.0) years in the control and dry eye groups, respectively (p=0.63). The median (IQR) values of the OSDI scores, tear film breakup time scores, and Schirmer's test measurements in the control groups were 10.4 (8.3 to 10.4), 12.0 (11.0 to 14.0) seconds, and 16.0 (13.5 to 19.5) mm, respectively, which differed from the dry eye groups (p<0.0001). These values in the dry eye group were 29.1 (25.0 to 39.5), 4.0 (3.0 to 8.0) seconds, and 8.0 (3.5 to 11.0) mm, respectively. Patients with dry eyes had lower central corneal thickness than controls (p<0.01). The mean ± standard deviation central corneal thicknesses in patients with dry eyes and the control group were 520.3 ± 26.8 and 545.3 ± 18.8 μm, respectively.

CONCLUSIONS

The central corneal thickness in dry eyes was significantly reduced compared with the control group. These findings may be useful in monitoring and managing dry eyes and should be considered in intraocular pressure measurements and refractive surgical procedures.

Analysis of Clinical Characteristics and Neuropeptides in Patients with Dry Eye with and without Chronic Ocular Pain after FS-LASIK

INTRODUCTION

Chronic ocular pain, particularly prevalent in patients with dry eye disease and post-femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) surgery, presents with unclear clinical characteristics and an undefined pathogenesis. In this study, we aimed to compare clinical characteristics and tear neuropeptide concentrations in patients with dry eye disease (DED) with and without chronic ocular pain following FS-LASIK, and investigate correlations between ocular pain, clinical characteristics, and tear neuropeptide levels.

METHODS

Thirty-eight post-FS-LASIK patients with DED were assigned to two groups: those with chronic ocular pain and those without chronic ocular pain. Dry eye, ocular pain, and mental health-related parameters were evaluated using specific questionnaires and tests. The morphology of corneal nerves and dendritic cells (DCs) was evaluated by in vivo confocal microscopy. Function of corneal innervation was evaluated by corneal sensitivity. Concentrations of tear cytokines (interleukin [IL]-6, IL-23, IL-17A, and interferon-γ) and neuropeptides (α-melanocyte-stimulating hormone, neurotensin, β-endorphin, oxytocin, and substance P [SP]) were measured using the Luminex assay.

RESULTS

Most patients with chronic ocular pain experienced mild to moderate pain; the most common types included stimulated pain (provoked by wind and light), burning pain, and pressure sensation. More severe dry eye (P < 0.001), anxiety symptoms (P = 0.026), lower Schirmer I test values (P = 0.035), lower corneal nerve density (P = 0.043), and more activated DCs (P = 0.041) were observed in patients with ocular pain. Tear concentrations of SP and oxytocin were significantly higher in patients with ocular pain (P = 0.001, P = 0.021, respectively). Furthermore, significant correlations were observed among ocular pain severity, SP, and anxiety levels.

CONCLUSIONS

Patients with DED after FS-LASIK who have chronic ocular pain show more severe ocular and psychological discomfort and higher tear levels of neuropeptides. Furthermore, ocular pain severity is correlated with tear SP levels.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05600985.

Relation Between Corneal Dendritic Cell Density and Tear Film Stability in Patients with Epidemic Keratoconjunctivitis Associated Dry Eye

PURPOSE

To clarify the ocular surface features of patients with recent history of epidemic keratoconjunctivitis (EKC) and the relation between corneal dendritic cells (DCs) and ocular discomfort.

METHODS

Normal controls (NC) and dry eye (DE) patients without EKC were recruited. Patients with recent EKC history (onset >4 weeks, but <20 weeks) were recruited as EKC + DE group (with dry eye) or EKC-DE group (without dry eye). Ocular surface disease index (OSDI) questionnaire, tear film parameters including lipid layer thickness, first tear break-up time (fBUT), average tear break-up time (aBUT), tear meniscus height and Schirmer I test, meibomian gland parameters, and in vivo corneal confocal microscopy were evaluated.

RESULTS

50 subjects in the NC group, 83 patients in the DE group, 76 patients in the EKC + DE group, and 38 patients in the EKC-DE group were included. Compared with the NC, DE, and EKC-DE groups, the EKC + DE group represented higher OSDI, lid margin, and meibum score (p < 0.05). In the EKC + DE group, the tear volume (10.5 ± 3.7 mm) was significantly higher than in the DE group (8.1 ± 2.8 mm, p < 0.001). The DC density in the EKC + DE group (29.98 ± 15.38 cells/image) was significantly higher than in NC, DE, and EKC-DE groups (4.68 ± 4.05 cells/image) (p < 0.001). The DC density was positively correlated with OSDI, lid margin, and meibum score (all p < 0.01) while inversely correlated with fBUT, aBUT (all p < 0.001) in the EKC + DE group.

CONCLUSIONS

Corneal DC density significantly correlates to ocular discomfort and tear film instability in patients with recent EKC history who suffer from DE without aqueous tear deficiency.

Corneal Epithelial Dendritic Cells: An Objective Indicator for Ocular Surface Inflammation in Patients with Obstructive Meibomian Gland Dysfunction?

PURPOSE

To examine whether corneal epithelial dendritic cells (CEDC) could serve as an indicator to distinguish obstructive meibomian gland dysfunction (MGD) with or without ocular surface inflammation (OSI).

METHODS

We performed a case-control study on patients with diagnosed obstructive MGD between August 2017 and November 2019.

RESULTS

30 MGD cases and 25 healthy controls were recruited. The classification of MGD patients with and without OSI was based on the tear pro-inflammatory cytokine levels. Compared with the MGD without OSI and the control group, a higher CEDC density was detected in the MGD with OSI subgroup. The presence of >15.6 cells/mm2 CEDC had a sensitivity of 73% and specificity of 75% for the diagnosis of MGD with OSI.

CONCLUSIONS

OSI is not present in all patients with obstructive MGD. Evaluation of CEDC density in the central cornea may help identify whether MGD is concomitant with OSI.

Confocal Microscopy Abnormalities Preceding Antibody Positivity and Manifestations of Sjogren's Syndrome

An asymptomatic 26-year-old woman underwent confocal microscopy as part of a control population for a research study. Images revealed reduced sub-basal corneal nerve density and multiple activated dendritic cells. Three years later, she presented with a self-limited cutaneous vasculitis in her lower extremities which prompted an evaluation for autoimmune diseases. Laboratory testing revealed positive antinuclear antibodies (1:320, thick granular pattern), and anti-SSA/SSB (SSA, 53.6 U/mL, moderately positive; SSB, 142.7 U/mL, strongly positive). Two weeks later, she presented with ocular pain and an ophthalmologic examination revealed ocular surface staining. An ocular ultrasound was consistent with posterior scleritis. Based on this picture, a diagnosis of Sjögren syndrome (SS) was made. SS is a chronic autoimmune disease that can present with symptoms that diminish the patient's quality of life. Confocal microscopy might be a valuable tool for the early diagnosis of disease.

Corneal immune cells as a biomarker of inflammation in multiple sclerosis: a longitudinal study

Background

Corneal immune cells (ICs) are antigen-presenting cells that are known to increase ocular and systemic inflammatory conditions.

Objective

We aimed to assess longitudinal changes in corneal IC in patients with multiple sclerosis (MS) and relation to disability and ongoing treatment.

Design

Prospective observational study conducted between September 2016 and February 2020.

Methods

Patients with relapsing-remitting MS (RRMS) (n = 45) or secondary progressive MS (SPMS) (n = 15) underwent corneal confocal microscopy (CCM) at baseline and 2-year follow-up for estimation of corneal IC density [dendritic cells with (DCF) (cells/mm2) or without nerve fiber contact (DCP); and non-dendritic cells with (NCF) or without nerve fiber contact (NCP)]. Optical coherence tomography, neuroimaging, and disability assessments were additionally performed. Healthy controls (n = 20) were assessed at baseline.

Results

In both RRMS and SPMS compared to controls, DCP (p < 0.001 and p < 0.001, respectively) and DCF (p < 0.001 and p = 0.005) were higher and NCF (p = 0.007 and p = 0.02) was lower at baseline. DCP showed excellent performance in identifying patients with MS (sensitivity/specificity = 0.88/0.90) followed by DCF (0.80/0.75) and NCF (0.80/0.85). At follow-up compared to baseline, DCP (p = 0.01) was significantly reduced, and NCP (p = 0.004) and NCF (p = 0.04) were increased. Subgroup analysis showed that baseline NCP and NCF were significantly higher (p = 0.04-0.05) in patients who switched disease-modifying treatment, and baseline NCP (p = 0.05) was higher in patients on interferon.

Conclusion

Baseline and change in corneal IC were related to axonal degeneration and treatment status. Evaluation of corneal IC using CCM may allow an assessment of ongoing inflammation, disease progression, and the effect of treatment in MS.

Increased dendritic cell density and altered morphology in allergic conjunctivitis

BACKGROUND

Corneal and conjunctival epithelial dendritic cells (DC) have an established role in vernal keratoconjunctivitis, however, their role in more prevalent forms of allergic eye disease remains unclear. This study evaluated corneal and conjunctival epithelial DC density, morphology, and distribution observed using in vivo confocal microscopy (IVCM) in allergic conjunctivitis.

METHODS

In this prospective, observational study, 66 participants (mean age 36.6 ± 12.0 years, 56% female): 33 with allergic conjunctivitis and 33 controls were recruited. IVCM was performed at the corneal centre, inferior whorl, corneal periphery, corneal limbus, and temporal bulbar conjunctiva. DC were counted and their morphology was assessed as follows: largest cell body size, presence of dendrites, and presence of long and thick dendrites. Mixed model analysis (DC density) and non-parametric tests (DC morphology) were used.

RESULTS

DC density was higher in allergic participants at all locations (p ≤ 0.01), (corneal centre median (IQR) 21.9 (8.7-50.9) cells/mm2 vs 13.1 (2.8-22.8) cells/mm2; periphery 37.5 (15.6-67.2) cells/mm2 vs 20 (9.4-32.5) cells/mm2; limbus 75 (60-120) cells/mm2 vs 58.1 (44.4-66.2) cells/mm2; conjunctiva 10 (0-54.4) cells/mm2 vs 0.6 (0-5.6) cells/mm2, but not at the inferior whorl 21.9 (6.2-34.4) cells/mm2 vs 12.5 (1.9-37.5) cells/mm2, p = 0.20. At the corneal centre, allergic participants had larger DC bodies (p = 0.02), a higher proportion of DC with dendrites (p = 0.02) and long dendrites (p = 0.003) compared to controls.

CONCLUSIONS

Corneal and conjunctival DC density was increased, and morphology altered in allergic conjunctivitis. These findings imply that the ocular surface immune response was upregulated and support an increased antigen-capture capacity of DC in allergic conjunctivitis.

Dendritiform immune cells with reduced antigen-capture capacity persist in the cornea during the asymptomatic phase of allergic conjunctivitis

BACKGROUND

Increased density and altered morphology of dendritic cells (DC) in the cornea and conjunctiva occur during active allergic conjunctivitis. This study investigated whether inflammation (characterised by altered DC density and morphology) persists during the symptom-free phase of allergic conjunctivitis.

METHODS

Twenty participants (age 43.3 ± 14.3 years, 55% female) assessed during their active (symptomatic) phase of allergic conjunctivitis were re-examined during the asymptomatic phase. Ocular allergy symptoms and signs were evaluated during both phases, and five ocular surface locations (corneal centre, inferior whorl, corneal periphery, corneal limbus, and bulbar conjunctiva) were examined using in vivo confocal microscopy (HRT III). DC were counted manually, and their morphology was assessed for cell body size, presence of dendrites, presence of long dendrites and presence of thick dendrites using a grading system. Mixed model analysis (DC density) and non-parametric tests (DC morphology) were used to examine differences between phases.

RESULTS

DC density at corneal locations did not change between the active and asymptomatic phases (p ≥ 0.22). However, corneal DC body size was smaller and fewer DC presented with long dendrites during the asymptomatic phase (p ≤ 0.02). In contrast, at the bulbar conjunctiva, DC density was reduced during the asymptomatic phase compared to the active phase (p = 0.01), but there were no changes in DC morphology.

CONCLUSIONS

Dendritiform immune cell numbers persist in the cornea during the symptom-free phase of allergic conjunctivitis, whereas conjunctival DC appear to return to a baseline state. The morphology of these persisting corneal DC suggests their antigen-capture capacity is reduced during the asymptomatic phase.

Association of Ocular Surface Immune Cells With Dry Eye Signs and Symptoms in the Dry Eye Assessment and Management (DREAM) Study

Purpose

Dry eye disease (DED) is a multifactorial, heterogeneous disease of the ocular surface with one etiology being ocular surface inflammation. Studies using animal models demonstrate the role of ocular surface immune cells in the inflammatory pathway leading to DED, but few have evaluated humans. This study described the white blood cell population from the ocular surface of patients with DED and assessed its association with DED signs and symptoms in participants of the Dry Eye Assessment and Management (DREAM) study.

Methods

Participants were assessed for symptoms using the Ocular Surface Disease Index, signs via corneal staining, conjunctival staining, tear break-up time, and Schirmer test, and Sjögren's syndrome (SS) based on the 2012 American College of Rheumatology classification criteria. Impression cytology of conjunctival cells from each eye was evaluated using flow cytometry: T cells, helper T cells (Th), regulatory T cells (Tregs), cytotoxic T cells, and dendritic cells.

Results

We assessed 1049 eyes from 527 participants. White blood cell subtype percentages varied widely across participants. Significant positive associations were found for Th and conjunctival staining (mean score of 2.8 for 0% Th and 3.1 for >4.0% Th; P = 0.007), and corneal staining (mean score of 3.5 for 0% Th and 4.3 for >4.0% Th; P = 0.01). SS was associated with higher percent of Tregs (median 0.1 vs. 0.0; P = 0.01).

Conclusions

Th were associated with more severe conjunctival and corneal staining, possibly indicating their role in inflammation leading to damage of the ocular surface. There is no consistent conclusion about Tregs in SS, but these results support that Tregs are elevated in SS.

Evaluation of Corneal Nerve Regeneration After Minimally Invasive Corneal Neurotization

PURPOSE

To evaluate the corneal nerve regeneration after minimally invasive corneal neurotization (MICN) and to further clarify the recovery patterns of sensory and trophic functions of the corneal nerves.

DESIGN

A retrospective cohort study based in the Shanghai Ninth People's Hospital.

METHODS

Eighteen patients (18 eyes) who underwent MICN for neurotrophic keratopathy due to intracranial surgery was conducted to analyze their follow-up data at 6, 12, 18, and 24 months after surgery.

RESULTS

At 12 months postoperatively, the growth of the central and peripheral corneal nerve fiber density (CNFD) was 11.47±8.56 and 14.73±8.08 n/mm 2 with subsequent improvement slowing down, and the patient's corneal epithelium defect was healed ahead of the accomplishment of corneal nerve regeneration. The number of dendritic cells also reached its peak. At 18 months postoperatively, the recovery of central and peripheral corneal sensation was 37.22±23.06 mm and 39.38±18.08 mm with no subsequent improvement, and the growth of the central and peripheral corneal nerve branch density (CNBD) was 29.69±11.05 and 43.75±1.41 n/mm 2 , with a positive and significant correlation between corneal sensation and CNBD (at central r =0.632, P <0.005; at peripheral r =0.645, P <0.005). At 24 months postoperatively, mean CNFD, CNBD, and corneal sensation recovered significantly compared with preoperative, but a few patients' corneal sensation recovered insignificantly with good CNFD recovery and poor CNBD recovery.

CONCLUSIONS

After MICN, the trophic function of the corneal nerve recovers before the sensory function, and in particular, the recovery of sensation is based on the coexistence of the corneal nerve trunk and branches.

Automated identification and quantification of activated dendritic cells in central cornea using artificial intelligence

PURPOSE

To validate an algorithm quantifying activated dendritic cells (aDCs) using in-vivo confocal microscopy (IVCM) images.

METHODS

IVCM images obtained at the Miami Veterans Affairs Hospital were retrospectively analyzed. ADCs were quantified both with an automated algorithm and manually. Intra-class-correlation (ICC) and a Bland-Altman plot were used to compare automated and manual counts. As a secondary analysis, individuals were grouped by Dry Eye (DE) subtype: 1) aqueous-tear deficiency (ATD; Schirmer's test ≤5 mm); 2) evaporative DE (EDE; TBUT≤5s); or 3) control (Schirmer's test>5 mm; TBUT>5s) and ICCs were re-examined.

RESULTS

173 non-overlapping images from 86 individuals were included in this study. The mean age was 55.2 ± 16.7 years; 77.9% were male; 20 had ATD; 18 EDE and 37 were controls. The mean number of aDCs in the central cornea quantified automatically was 0.83 ± 1.33 cells/image and manually was 1.03 ± 1.65 cells/image. A total of 143 aDCs were identified by the automated algorithm and 178 aDCs were identified manually. While a Bland-Altman plot indicated a small difference between the two methods (0.19, p < 0.01), the ICC of 0.80 (p = 0.01) demonstrated excellent agreement. Secondarily, similar results were found by DE type with an ICC of 0.75 (p = 0.01) for the ATD group, 0.80 (p = 0.01) for EDE, and 0.82 (p = 0.01) for controls.

CONCLUSIONS

Quantification of aDCs within the central cornea may be successfully estimated using an automated machine learning based algorithm. While this study suggests that analysis using artificial intelligence has comparable results with manual quantification, further longitudinal research to validate our findings in more diverse populations may be warranted.

In-vivo corneal confocal microscopy: Imaging analysis, biological insights and future directions

In-vivo corneal confocal microscopy is a powerful imaging technique which provides clinicians and researcher with the capabilities to observe microstructures at the ocular surfaces in significant detail. In this Mini Review, the optics and image analysis methods with the use of corneal confocal microscopy are discussed. While novel insights of neuroanatomy and biology of the eyes, particularly the ocular surface, have been provided by corneal confocal microscopy, some debatable elements observed using this technique remain and these are explored in this Mini Review. Potential improvements in imaging methodology and instrumentation are also suggested.

The Association between Autoimmune Thyroid Disease and Ocular Surface Damage: A Retrospective Population-Based Cohort Study

Autoimmune thyroid diseases (ATDs) are potentially connected to lacrimal gland dysfunction and ocular surface disruption. This study aimed to evaluate the relationships between ATD, dry eye disease (DED), and corneal surface damage. In a matched nationwide cohort study, we used Taiwan's National Health Insurance research database to compare the incidences of DED and corneal surface damage between subjects with and without ATD. Multivariable Cox proportional hazards regression models were used to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) for the ophthalmological outcomes. A total of 50,251 matched pairs with 748,961 person-years of follow-up were included for analysis. The incidence of DED was 16.37 and 8.36 per 1000 person-years in the ATD and non-ATD groups, respectively. ATDs were significantly associated with increased DED (aHR: 1.81, 95% CI: 1.73-1.89, p < 0.0001). This association was generally consistent across the subgroups of age, sex, different comorbidity levels, and use of systemic corticosteroids or not. Furthermore, patients with ATD had a higher risk of corneal surface damage compared with non-ATD subjects (aHR: 1.31, 95% CI: 1.19-1.44, p < 0.0001), including recurrent corneal erosions (aHR: 2.00, 95% CI: 1.66-2.41, p < 0.0001) and corneal scars (aHR: 1.26, 95% CI: 1.01-1.59, p = 0.0432). Other independent factors for corneal surface damage were age, sex, diabetes mellitus, Charlson Comorbidity Index scores, and use of systemic corticosteroids. Our results suggested that ATDs were associated with higher risks of DED and corneal surface damage. Considering the high prevalence of ATD, prophylactic and therapeutic strategies should be further developed to prevent irreversible vision loss in this susceptible population.

Involvement of RNA methylation modification patterns mediated by m7G, m6A, m5C and m1A regulators in immune microenvironment regulation of Sjögren's syndrome

Keratoconjunctivitis is the most common complication of Sjögren's syndrome (SS). It has always been a hot research topic due to its complex pathogenesis. A further understanding of keratoconjunctiva xerosis can be obtained by studying the primary diseases. 7-Methylguanine (m7G), N6-methyladenosine (m6A), 5-methylcytosine (m5C), and N1-methyladenosine (m1A) are newly discovered epigenetic mechanisms involved in the development of SS. This study aimed to investigate the effects of m7G, m6A, m5C, and m1A modifications on the immune microenvironment of SS. Three microarray datasets were downloaded from the Gene Omnibus Expression (GEO) database, including 56 SS samples and 35 normal samples. Then, genes with m7G, m6A, m5C, and m1A methylation were explored, and the RNA modification patterns mediated by 59 m7G, m6A, m5C, and m1A regulators were summarized. The effects of m7G, m6A, m5C, and m1A modifications on immune infiltrating cells were discussed. Eukaryotic translation initiation factor 3 subunit D(EIF3D) was closely related to monocytes, and the expression of EIF3D was higher in SS with less monocytes. Two distinct patterns of RNA modification mediated by the 59 m7G, m6A, m5C, and m1A regulators were also identified, which infiltrated immune cells differently. Moreover, the two distinct RNA patterns were enriched in different signaling pathways, and their biological functions were explored. The findings revealed that m7G, m6A, m5C, and m1A modifications played vital roles in the diversity and complexity of the immune microenvironment in SS.

Diurnal changes and topographical distribution of ocular surface epithelial dendritic cells in humans, and repeatability of density and morphology assessment

PURPOSE

Dendritic cells (DC) play a crucial role in ocular surface defence. DC can be visualised in vivo by confocal microscopy but have not yet been fully characterised in humans. This study investigated the diurnal variation, topographical distribution and repeatability of DC density and morphology measurements.

METHODS

In vivo confocal microscopy (IVCM) was conducted on 20 healthy participants (mean age 32.7 ± 6.4 years, 50% female) at baseline and repeated after 30 minutes, 2, 6 and 24 h. Images were captured at the corneal centre, inferior whorl, corneal periphery, limbus and bulbar conjunctiva. DC were counted manually, and their morphology was assessed for cell body size, presence of dendrites, and presence of long and thick dendrites. Mixed-model analysis, non-parametric analyses, Bland and Altman plots, coefficient of repeatability (CoR) and kappa were used.

RESULTS

There were no significant changes in DC density (p ≥ 0.74) or morphology (p > 0.07) at any location over the 24-h period. The highest DC density was observed at the corneal limbus followed by the peripheral cornea (p < 0.001), with the lowest density at the corneal centre, inferior whorl and bulbar conjunctiva. Most DC at the corneal periphery, limbus and bulbar conjunctiva had larger cell bodies compared with the corneal centre (p ≤ 0.01), and the presence of long dendrites was observed mostly at non-central locations. Day-to-day CoR for DC density ranged from ±28.1 cells/mm² at the corneal centre to ±56.4 cells/mm² at the limbus. Day-to-day agreement of DC morphology determined by kappa ranged from 0.5 to 0.95 for cell body size, 0.60 to 0.95 for presence of dendrites, and 0.55 to 0.80 for the presence of long dendrites at various locations.

CONCLUSIONS

No diurnal changes are apparent in corneal or conjunctival DC. Substantial topographical differences exist in DC density and morphology. IVCM provides good repeatability of DC density and acceptable agreement of DC morphology.

Mesenchymal Stromal Cells-Derived Extracellular Vesicles Regulate Dendritic Cell Functions in Dry Eye Disease

We explored the therapeutic efficacy of Mesenchymal stromal cells-derived extracellular vesicles (MSC-EVs) and its inhibition of the functions of dendritic cells (DCs) in dry eye disease (DED). MSC-EVs were isolated from the culture supernatants of mesenchymal stromal cells (MSCs) and characterized. In vitro, human corneal epithelial cells (HCECs) were cultured in hyperosmotic medium to simulate the DED hyperosmotic environment and treated with MSC-EVs. Cell viability was assessed, and the expression of inflammatory cytokines was quantified. Next, we induced DED in female C57BL/6 mice and divided the mice into groups treated with either MSC-EVs or phosphate buffer solution (PBS) eye drops. Disease severity was assessed; mRNA expression of inflammatory cytokines was analyzed by RT-PCR; and Th17 cells were detected by flow cytometry. Lastly, we evaluated DCs by immunofluorescence and flow cytometric analysis to assess its amounts and maturation. MSC-EVs showed protective effects on HCECs under hyperosmotic stress in vitro, suppressing the expression of inflammatory cytokines. In vivo, mice topically treated with MSC-Evs presented reduced DED disease severity compared to PBS-treated mice. MSC-Evs downregulated the expression of inflammatory cytokines, including TNF-α, IL-6, and IL-1β, as well as the frequency of Th17 cells. Further investigation showed that MSC-EVs suppressed the increase of amounts and the maturation of DCs in DED. Changes of morphological characters of DCs were also inhibited by MSC-EVs. Our study revealed that MSC-EVs suppressed ocular surface inflammation by inhibiting DCs activation-mediated Th17 immune responses, explicating the therapeutic potential of MSC-EVs in DED and other ocular surface diseases.

Corneal epithelial dendritic cells, tear neuropeptides and corneal nerves continue to be affected more than 12 months after LASIK

PURPOSE

LASIK causes corneal nerve damage and may affect the neuro-immune crosstalk. This study examined the effects of LASIK on corneal epithelial dendritic cells (CEDC) density and morphology and explored their relationships with corneal nerves and tear neuropeptides. A grading system was developed to assess CEDC morphology.

METHODS

Intra- and inter-observer repeatability of the CEDC morphology grading system was established using kappa (κ). In vivo confocal microscope images of the central cornea were captured from 20 participants who had undergone LASIK 12-16 months earlier and 20 controls (age 18-32 years, 55%F). CEDC density was counted manually, and CEDC morphology was assessed using a new grading system. CEDC sub-types (contacting nerves [CEDCc] and not contacting nerves [CEDCnc]) were also assessed. Differences in CEDC density and morphology were examined using mixed models and chi-squared test. Relationships between CEDC and corneal nerve parameters and tear substance P were explored using Spearman's correlation.

RESULTS

Excellent intra- and inter-observer repeatability was demonstrated for the grading system (κ = 0.82-0.97). In post-LASIK participants, CEDC density was lower compared with controls (5 [0-34] vs. 21 [7-77] cells/mm² ; p = 0.01), and the proportion of CEDC with thick dendrites was higher (55%-73% vs. 11%-21%, p < 0.003). Higher tear substance P levels were associated with higher CEDC density (rho = 0.48, p = 0.003). Fewer nerve interconnections were observed in participants in whom CEDC had dendrites (p = 0.03). CEDC sub-types followed a similar pattern to CEDC.

CONCLUSIONS

The findings suggest that CEDC may remain altered more than 12 months post-LASIK. The association with substance P suggests a role for CEDC in corneal neurogenic inflammation.

Density and distribution of dendritiform cells in the peripheral cornea of healthy subjects using in vivo confocal microscopy

PURPOSE

To establish dendritiform cell (DC) density and morphological parameters in the central and peripheral cornea in a large healthy cohort, using in vivo confocal microscopy (IVCM).

METHODS

A prospective, cross-sectional, observational study was conducted in 85 healthy volunteers (n = 85 eyes). IVCM images of corneal center and four peripheral zones were analyzed for DC density and morphology to compare means and assess correlations (p < 0.05 being statistically significant).

RESULTS

Central cornea had lower DC density (40.83 ± 5.14 cells/mm²; mean ± SEM) as compared to peripheral cornea (75.42 ± 2.67 cells/mm², p < 0.0001). Inferior and superior zones demonstrated higher DC density (105.01 ± 7.12 and 90.62 ± 4.62 cells/mm²) compared to the nasal and temporal zones (59.93 ± 3.42 and 51.77 ± 2.98 cells/mm², p < 0.0001). Similarly, lower DC size, field and number of dendrites were observed in the central as compared to the average peripheral cornea (p < 0.0001), with highest values in the inferior zone (p < 0.001 for all, except p < 0.05 for number of dendrites in superior zone). DC parameters did not correlate with age or gender. Inter-observer reliability was 0.987 for DC density and 0.771-0.922 for morphology.

CONCLUSION

In healthy individuals, the peripheral cornea demonstrates higher DC density and larger morphology compared to the center, with highest values in the inferior zone. We provide the largest normative cohort for sub-stratified DC density and morphology, which can be used in future clinical trials to compare differential changes in diseased states. Furthermore, as DC parameters in the peripheral zones are dissimilar, random sampling of peripheral cornea may be inaccurate.

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.

Alterations in corneal epithelial dendritic cell in Sjogren's syndrome dry eye and clinical correlations

We aimed to investigate the density and morphology of corneal dendritic cells (DCs) in dry eye (DE) patients with or without Sjogren’s syndrome (SS). This study included 28 patients with Sjogren’s syndrome dry eye (SSDE), 33 patients with non-Sjogren’s syndrome dry eye (NSSDE), and 30 age and sex matched healthy volunteers. In vivo confocal microscopy (IVCM) was used to investigate density and morphology (size, dendrites, and field) of DC. Compared with NSSDE and healthy group, SSDE showed significantly higher DC density, larger DC size, more DC dendrites with larger DC field (all P < 0.001). Comparison between NSSDE and healthy group demonstrated that DC density, dendrites and field were significantly higher in NSSDE. However, there was no significant difference in DC size (P = 0.076). DC density and morphological parameters showed significant associations with the systemic severity (salivary gland biopsy and serum antibodies) and ocular surface damage. The corneal epithelium DC density and morphological alterations were obvious in SSDE, which reflected higher level of immune activation and inflammatory response in SS. Marked correlations were found between DC density/morphology and systemic/ocular severity. Dynamic assessment of corneal DC may facilitate to clarify pathogenesis, stratify patient, and tailor treatment in SS patients.

Defining an Optimal Sample Size for Corneal Epithelial Immune Cell Analysis Using in vivo Confocal Microscopy Images

Purpose

In vivo confocal microscopy (IVCM) images are frequently used to quantify corneal epithelial immune cell (IC) density in clinical studies. There is currently limited evidence to inform the selection of a representative image sample size to yield a reliable IC density estimate, and arbitrary numbers of images are often used. The primary aim of this study was to determine the number of randomly selected, unique IVCM images required to achieve an acceptable level of accuracy when quantifying epithelial IC density, in both the central and peripheral cornea. The secondary aim was to evaluate the consistency and precision of an image selection approach where corneal epithelial IC density was quantified from "three representative images" selected independently by three experienced observers.

Methods

All combinations of two to 15 non-overlapping IVCM images were used for deriving IC density estimates, for both the central and peripheral cornea, in 20 healthy participants; the density value from averaging quantifications in the 16 images was defined as the "true mean". IC density estimates were compared with the true mean in each corneal region using a mean ratio. Intraclass correlation coefficients (ICCs) were used to evaluate the consistency of the mean ratios of IC density estimates derived from the method involving the manual selection of "three representative images" by the observers. The precision of the IC density estimates was compared to a scenario involving three randomly selected images.

Results

A total of 12 randomly selected, non-overlapping IVCM images were found to be required to produce a corneal epithelial IC density estimate that was within 30% of the true mean, 95% of the time, for the central cornea; seven such images produced an equivalent level of precision in the peripheral cornea. Mean ratios of corneal IC density estimates derived from "three representative images" methods had poor consistency between observers (ICC estimates <0.5) and similar levels of precision when compared with using three randomly selected images (p > 0.05 for all comparisons), in both the central and peripheral cornea.

Conclusions

Data presented in this study can inform image selection methods, and the sample size required for a preferred level of accuracy, when quantifying IC densities in the central and peripheral corneal epithelium using IVCM images.

Corneal Epithelium-Derived Netrin-1 Alleviates Dry Eye Disease via Regulating Dendritic Cell Activation

Purpose

To investigate the expression of corneal epithelium-derived netrin-1 (NTN-1) and its immunoregulatory function in dry eye disease (DED) using a DED mouse model.

Methods

We generated DED mouse models with desiccating stress under scopolamine treatment. RNA sequencing was performed to identify differentially expressed genes (DEGs) in the corneal epithelium of DED mice. NTN-1 expression was analyzed via real-time PCR, immunofluorescence staining, and immunoblotting. The DED mice were then treated with recombinant NTN-1 or neutralizing antibodies to investigate the severity of the disease, dendritic cell (DC) activation, and inflammatory cytokine expression.

Results

A total of 347 DEGs (292 upregulated and 55 downregulated) were identified in the corneal epithelium of DED mice: corneal epithelium-derived NTN-1 expression was significantly decreased in DED mice compared to that in control mice. Topical recombinant NTN-1 application alleviated the severity of the disease, accompanied by restoration of tear secretion and goblet cell density. In addition, NTN-1 decreased the number of DCs, inhibited the activation of the DCs and Th17 cells, and reduced the expression of inflammatory factors in DED mice. In contrast, blocking endogenous NTN-1 activity with an anti-NTN-1 antibody aggravated the disease, enhanced DC activation, and upregulated the inflammatory factors in the conjunctivae of DED mice.

Conclusions

We identified decreased NTN-1 expression in the corneal epithelium of DED mice. Our findings elucidate the role of NTN-1 in alleviating DED and impeding DC activation, thereby indicating its therapeutic potential in suppressing ocular inflammation in DED.

Corneal immune cell morphometry as an indicator of local and systemic pathology: A review

The corneal epithelium contains a population of resident immune cells commonly referred to as dendritic cells (DCs), or Langerhans cells. A unique advantage of the transparent cornea being situated at the surface of the eye is that these cells can be readily visualised using in vivo confocal microscopy. Over the past decade, interest in the involvement of corneal DCs in a range of ocular and systemic diseases has surged. For most studies, the number of corneal DCs has been the main outcome of interest. However, more recently attention has shifted towards understanding how DC morphology may provide insights into the inflammatory status of the cornea, and in some cases, the health of the peripheral nervous system. In this review, we provide examples of recent methodologies that have been used to classify and measure corneal DC morphology and discuss how this relates to local and systemic inflammatory conditions in humans and rodents.