Conjunctival goblet cells: Ocular surface functions, disorders that affect them, and the potential for their regeneration

Therapeutic application of decellularized porcine small intestinal submucosa scaffold in conjunctiva reconstruction

The objective of this study was to investigate the biological feasibility and surgical applicability of decellularized porcine small intestinal submucosa (DSIS) in conjunctiva reconstruction. A total of 52 Balb/c mice were included in the study. We obtained the DSIS by decellularization, evaluated the physical and biological properties of DSIS in vitro, and further evaluated the effect of surgical transplantation of DSIS scaffold in vivo. The histopathology and ultrastructural analysis results showed that the scaffold retained the integrity of the fibrous morphology while removing cells. Biomechanical analysis showed that the elongation at break of the DSIS (239.00 ± 12.51%) were better than that of natural mouse conjunctiva (170.70 ± 9.41%, P < 0.05). Moreover, in vivo experiments confirmed the excellent biocompatibility of the decellularized scaffolds. In the DSIS group, partial epithelialization occurred at day-3 after operation, and the conjunctival injury healed at day-7, which was significantly faster than that in human amniotic membrane (AM) and sham surgery (SHAM) group (P < 0.05). The number and distribution of goblet cells of transplanted DSIS were significantly better than those of the AM and SHAM groups. Consequently, the DSIS scaffold shows excellent biological characteristics and surgical applicability in the mouse conjunctival defect model, and DSIS is expected to be an alternative scaffold for conjunctival reconstruction.

Protein profiling of conjunctival impression cytology samples of aniridia subjects

PURPOSE

Congenital aniridia is a rare disease, which is in most cases related to PAX6 haploinsufficiency. Aniridia associated keratopathy (AAK) also belongs to ocular signs of congenital aniridia. In AAK, there is corneal epithelial thinning, corneal inflammation, vascularization and scarring. In advanced stage AAK, typically, conjunctival epithelial cells slowly replace the corneal epithelium. Based on previous results we hypothesize that alterations of the conjunctival cells in congenital aniridia may also support the corneal conjunctivalization process. The aim of this study was to identify deregulated proteins in conjunctival impression cytology samples of congenital aniridia subjects.

METHODS

Conjunctival impression cytology samples of eight patients with congenital aniridia [age 34.5 ± 9.9 (17-51) years, 50% female] and eight healthy subjects [age 34.1 ± 11.9 (15-54) years, 50% female] were collected and analysed using mass spectrometry. Proteomic profiles were analysed in terms of molecular functions, biological processes, cellular components and pathway enrichment using the protein annotation of the evolutionary relationship (PANTHER) classification system.

RESULTS

In total, 3323 proteins could be verified and there were 127 deregulated proteins (p < 0.01) in congenital aniridia. From the 127 deregulated proteins (DEPs), 82 altered biological processes, 63 deregulated cellular components, 27 significantly altered molecular functions and 31 enriched signalling pathways were identified. Pathological alteration of the biological processes and molecular functions of retinol binding and retinoic acid biosynthesis, as well as lipid metabolism and apoptosis related pathways could be demonstrated.

CONCLUSIONS

Protein profile of conjunctival impression cytology samples of aniridia subjects identifies alterations of retinol binding, retinoic acid biosynthesis, lipid metabolism and apoptosis related pathways. Whether these changes are directly related to PAX6 haploinsufficiency, must be investigated in further studies. These new findings offer the possibility to identify potential new drug targets.

A CXCR3-Activating Peptide Increases Tear Break Up Time and Corrects Corneal haze in a Rabbit Model of Environmental Dry Eye

Purpose

Environmentally-triggered dry eye disease (DED) or keratoconjunctivitis sicca (KCS), which constitutes the majority of DED cases, currently is palliatively treated with aqueous replacement solutions that do not target the dysfunction of the mucin and lipid components of tears. We tested whether a peptide that increased goblet cell numbers in a model of scleral chemical injury would also improve tear quality in environmental DED.

Methods

Environmental DED was established by exposing New Zealand white rabbits (8 per group, female) to 20% humidity with rapid air replacement and b.i.d. atropine sulfate eyedrops for 3 weeks prior to test article administration; this continued for the subsequent 3 weeks of testing. Animals were dosed by (A) saline, (B) b.i.d. eyedrop of peptide in saline, (C) b.i.d. eyedrop of peptide in coacervate, or (D) weekly subconjunctival injection of peptide. In vitro, human conjunctival epithelial cells (HCjE) were exposed to TNFα in the presence or absence of peptide to determine inflammatory responsiveness.

Results

The environmental DED was established with both Schirmer and TBUT being reduced at the start of test article; these levels were maintained as low through the testing period. All three treatment regimens increased TBUT approximately 3x to levels greater than prior to desiccation (P < 0.01), with little effect on Schirmer. Corneal haze was present in all eyes after induction, and completely reversed in 36 of 48 eyes across the treatments (P < 0.05). Co-treatment of HCjE with peptide reduced the production of TNFα in response to an inflammatory stimulus.

Conclusions

The treatment of environmental DED/KCS with a peptide that activates CXCR3 improved tear quality and reversed corneal pathology by promoting tear stability and likely dampening the corneal inflammation, while not affecting aqueous volume of the tears.

Ocular surface disease in moderate-to-severe atopic dermatitis patients and the effect of biological therapy

Atopic dermatitis (AD) is a chronic inflammatory skin disease for which new targeted therapies are currently available. Due to the increased rates of ocular surface disease (OSD) reported during treatment with these new targeted treatments, more insight into the occurrence and pathomechanism of OSD in moderate-to-severe AD patients is needed. Therefore, this review's first part highlights that most patients with moderate-to-severe AD already have characteristics of OSD before starting targeted treatment. Remarkably, not all AD patients with OSD report ocular symptoms. OSD in AD is associated with less conjunctival goblet cells (GC) compared to healthy controls. In addition, OSD severity in AD patients is associated with high AD activity, the presence of eyelid and/or facial eczema, and high levels of AD-related severity biomarkers in tear fluid. The second part of this review highlights that pre-existing ocular pathology (e.g. in combination with the use of ophthalmic medication or eyelid eczema) may be associated with the development of dupilumab-associated ocular surface disease (DAOSD). During dupilumab treatment, DAOSD (which can be new-onset OSD or worsening of pre-existing OSD) is observed in approximately one-third of the dupilumab-treated AD patients. Anti-inflammatory ophthalmic treatment improves DAOSD, and dose reduction of dupilumab may also be an effective treatment option. The pathomechanism of DAOSD is still not fully elucidated. In a prospective study low, but stable conjunctival GC numbers were observed in moderate-to-severe AD patients, before and during dupilumab treatment. However, the Mucin 5 AC (MUC5AC) expression of GCs decreased during dupilumab treatment, suggesting an impairment of the GC function by dupilumab treatment. In addition, higher dupilumab tear fluid levels were found in dupilumab-treated AD patients with moderate-to-severe OSD compared to patients with no or mild OSD, whereas the dupilumab serum levels are similar. Clinicians should be aware of the frequent occurrence of OSD in moderate-to-severe AD patients, and a low-threshold referral to an ophthalmologist is recommended.

The miR-183/96/182 cluster regulates sensory innervation, resident myeloid cells and functions of the cornea through cell type-specific target genes

The conserved miR-183/96/182 cluster (miR-183C) is expressed in both corneal resident myeloid cells (CRMCs) and sensory nerves (CSN) and modulates corneal immune/inflammatory responses. To uncover cell type-specific roles of miR-183C in CRMC and CSN and their contributions to corneal physiology, myeloid-specific miR-183C conditional knockout (MS-CKO), and sensory nerve-specific CKO (SNS-CKO) mice were produced and characterized in comparison to the conventional miR-183C KO. Immunofluorescence and confocal microscopy of flatmount corneas, corneal sensitivity, and tear volume assays were performed in young adult naïve mice; 3' RNA sequencing (Seq) and proteomics in the trigeminal ganglion (TG), cornea and CRMCs. Our results showed that, similar to conventional KO mice, the numbers of CRMCs were increased in both MS-CKO and SNS-CKO vs age- and sex-matched WT control littermates, suggesting intrinsic and extrinsic regulations of miR-183C on CRMCs. The number of CRMCs was increased in male vs female MS-CKO mice, suggesting sex-dependent regulation of miR-183C on CRMCs. In the miR-183C KO and SNS-CKO, but not the MS-CKO mice, CSN density was decreased in the epithelial layer of the cornea, but not the stromal layer. Functionally, corneal sensitivity and basal tear volume were reduced in the KO and SNS-CKO, but not the MS-CKO mice. Tear volume in males is consistently higher than female WT mice. Bioinformatic analyses of the transcriptomes revealed a series of cell-type specific target genes of miR-183C in TG sensory neurons and CRMCs. Our data elucidate that miR-183C imposes intrinsic and extrinsic regulation on the establishment and function of CSN and CRMCs by cell-specific target genes. miR-183C modulates corneal sensitivity and tear production through its regulation of corneal sensory innervation.

Polymers and Biomaterials for Posterior Lamella of the Eyelid and the Lacrimal System

The application of biopolymers in the reconstruction of the posterior lamella of the eyelid and the lacrimal system marks a significant fusion of biomaterial science with clinical advancements. This review assimilates research spanning 2015 to 2023 to provide a detailed examination of the role of biopolymers in reconstructing the posterior lamella of the eyelid and the lacrimal system. It covers the anatomy and pathophysiology of eyelid structures, the challenges of reconstruction, and the nuances of surgical intervention. This article progresses to evaluate the current gold standards, alternative options, and the desirable properties of biopolymers used in these intricate procedures. It underscores the advancements in the field, from decellularized grafts and acellular matrices to innovative natural and synthetic polymers, and explores their applications in lacrimal gland tissue engineering, including the promise of 3D bioprinting technologies. This review highlights the importance of multidisciplinary collaboration between material scientists and clinicians in enhancing surgical outcomes and patient quality of life, emphasizing that such cooperation is pivotal for translating benchtop research into bedside applications. This collaborative effort is vital for restoring aesthetics and functionality for patients afflicted with disfiguring eyelid diseases, ultimately aiming to bridge the gap between innovative materials and their clinical translation.

Assessment of Mucin-Associated Gene Expression Levels on the Ocular Surface

The ocular surface is covered with a mucus layer. The mucin-associated genes expressed in the ocular surface cells include MUC1, MUC4, MUC5AC, and MUC16. Impression cytology is useful for collecting specimens from the ocular surface, their histological examination, and measuring mucin-associated gene expression levels. The expression of mucin-associated gene levels was assessed by quantitative polymerase chain reaction. The expression levels of these mucin-associated genes are potential biomarkers for ocular surface diseases, including dry eye disease.

Mitochondria-targeted SkQ1 nanoparticles for dry eye disease: Inhibiting NLRP3 inflammasome activation by preventing mitochondrial DNA oxidation

Dry eye disease (DED) is a multifactorial ocular surface disorder mutually promoted by reactive oxygen species (ROS) and ocular surface inflammation. NLRP3 is the key regulator for inducing ocular surface inflammation in DED. However, the mechanism by which ROS influences the bio-effects of NLRP3, and the consequent development of DED, largely remains elusive. In the present study, we uncovered that robust ROS can oxidate mitochondrial DNA (ox-mtDNA) along with loss of mitochondria compaction causing the cytosolic release of ox-mtDNA and subsequent co-localization with cytosolic NLRP3, which can promote the activation of NLRP3 inflammasome and stimulate NLRP3-mediated inflammation. Visomitin (also known as SkQ1), a mitochondria-targeted anti-oxidant, could reverse such a process by in situ scavenging of mitochondrial ROS. To effectively deliver SkQ1, we further developed a novel mitochondria-targeted SkQ1 nanoparticle (SkQ1 NP) using a charge-driven self-assembly strategy. Compared with free SkQ1, SkQ1 NPs exhibited significantly higher cytosolic- and mitochondrial-ROS scavenging activity (1.7 and 1.9 times compared to levels of the free SkQ1 group), thus exerting a better in vitro protective effect against H2O2-induced cell death in human corneal epithelial cells (HCECs). After topical administration, SkQ1 NPs significantly reduced in vivo mtDNA oxidation, while suppressing the expressions of NLRP3, Caspase-1, and IL-1β, which consequently resulted in better therapeutic effects against DED. Results suggested that by efficiently scavenging mitochondrial ROS, SkQ1 NPs could in situ inhibit DED-induced mtDNA oxidation, thus blocking the interaction of ox-mtDNA and NLRP3; this, in turn, suppressed NLRP3 inflammasome activation and NLRP3-mediated inflammatory signaling. Results suggested that SkQ1 NPs have great potential as a new treatment for DED.

Comparison of Transcriptomic Analysis of the Conjunctiva in Glaucoma-Treated Eyes with Dry Eyes and Healthy Controls

Ocular surface disease (OSD) associated with topical glaucoma drugs is a common issue impacting treatment adherence. We aimed to identify conjunctival transcriptomic changes in glaucoma and dry eye patients, comparing them to healthy controls. Bulbar conjunctival specimens were collected via impression cytology from 33 patients treated for glaucoma, 9 patients with dry eye, and 14 healthy controls. RNA extraction and bulk RNA sequencing were performed, followed by bioinformatics analysis to detect gene dysregulation. Ingenuity pathways analysis (IPA) identified pathways and biological processes associated with these transcriptomic changes. Sequencing analysis revealed 200 modified genes in glaucoma patients compared to healthy individuals, 233 differentially expressed genes in dry eye patients versus controls, and 650 genes in treated versus dry eye samples. In glaucoma patients, 79% of altered pathways were related to host defense, while dry eye patients showed a 39% involvement of host response, 15% in cellular proliferation and integrity, and 16% of mitochondrial dysfunction. These findings were validated through qRT-PCR. Glaucoma patients showed an intensified conjunctival immune response as a potential cause of OSD, whereas in dry eye patients, in addition to the immune response, other mechanisms such as mitochondrial dysfunction or reduced cellular proliferation were observed.

The Effect of Autografts from the Inferior and Superior Bulbar Conjunctiva on the Ocular Surface in Primary Pterygium Surgery: A Cytology Study

Objectives

This study aimed to evaluate the effect of using an inferior or superior conjunctival autograft in primary pterygium surgery on the postoperative ocular surface.

Materials and Methods

Forty eyes of 40 patients who underwent pterygium surgery with autograft were included in the study. Cytological cell counts were performed on samples taken from the bulbar conjunctiva by impression cytology before and 1 year after the operation. Schirmer 1 test score, lissamine green conjunctival staining score, tear film break-up time (TBUT), and fluorescein corneal staining scores were evaluated. The pain levels of the patients were evaluated with visual analog scale at postoperative 1 day and 1 week.

Results

Corneal and conjunctival staining, TBUT, and Schirmer test results demonstrated significant improvement in all patient groups after surgery, but there was no difference between groups (p>0.05). In both preoperative and postoperative impression cytology, the number of goblet cells in the inferior bulbar conjunctiva was higher than in the superior bulbar conjunctiva (p<0.001), while there was no such difference in epithelial cell or mucin staining. There were no significant cytological changes postoperatively in either group (p>0.05).

Conclusion

Pterygium surgery with autografting improved tear function tests regardless of graft location. Goblet cell count was higher in the inferior bulbar conjunctiva than in the superior bulbar conjunctiva in both postoperative and preoperative impression cytology. However, there was no significant difference in postoperative epithelial and goblet cell counts or mucin staining between the groups before and after surgery. We think that using the inferior bulbar conjunctiva is an appropriate choice in cases where the superior conjunctiva cannot be used as a graft or when future glaucoma surgery is possible.

The use of benzalkonium chloride in topical glaucoma treatment: An investigation of the efficacy and safety of benzalkonium chloride-preserved intraocular pressure-lowering eye drops and their effect on conjunctival goblet cells

ENGLISH SUMMARY

Glaucoma is a leading cause of the global prevalence of irreversible blindness. The pathogenesis of glaucoma is not entirely known, but the major risk factors include advancing age, genetic predisposition, and increased intraocular pressure (IOP). The only evidence-based treatment is a lowering of IOP through the use of eye drops, laser procedures, or surgical interventions. Although laser treatment is gaining recognition as a first-choice treatment option, the most common approach for managing glaucoma is IOP-lowering eye drops. A major challenge in the treatment is the occurrence of adverse events and poor adherence. In this context, the ocular surface is an area of great concern, as most glaucoma patients have dry eye disease (DED), which is largely caused by eye drops. Preservation with benzalkonium chloride (BAK) is a controversial topic due to its potential role as a significant cause of DED. A systematic review and meta-analyses investigate potential differences in efficacy and safety between BAK-preserved and BAK-free anti-glaucomatous eye drops (I). Many of the included studies report on ocular surface damage caused by the application of BAK-preserved eye drops. However, the meta-analyses addressing hyperemia, number of ocular adverse events, and tear break-up time did not identify any significant differences. The latter is likely due to varying measurement methods, different endpoints, and study durations. It is, therefore, possible that the large variations between the studies conceal differences in the safety profiles. The efficacy meta-analysis finds that there are no differences in the IOP-lowering effect between BAK-preserved and BAK-free eye drops, indicating that BAK is not necessary for the effectiveness of eye drops. To promote more homogeneous choices of endpoints and methods when evaluating BAK-preserved and BAK-free glaucoma treatments, a Delphi consensus statement was performed. In this study, glaucoma experts and ocular surface disease experts reached consensus on the key factors to consider when designing such studies (II). The hope is to have more studies with comparable endpoints that can systematically show the potentially adverse effects of BAK. The preclinical studies in the current Ph.D. research focus on conjunctival goblet cells (GCs). GCs are important for the ocular surface because they release the mucin MUC5AC, which is an essential component of the inner layer of the tear film. BAK preservation may damage the GCs and result in a low GC density, leading to an unstable tear film and DED. The most commonly used IOP-lowering drugs are prostaglandin analogs (PGAs). Thus, the conducted studies investigate the effect of PGAs preserved in different ways on GCs. BAK-preserved latanoprost is cytotoxic to primary cultured human conjunctival GCs and results in a scattered expression of MUC5AC, in contrast to negative controls, where MUC5AC is localized around the cell nucleus (III). Preservative-free (PF) latanoprost is not cytotoxic and does not affect the MUC5AC expression pattern. Furthermore, BAK-preserved travoprost is found to be cytotoxic in a time-dependent manner, while Polyquad®-preserved travoprost does not affect GC survival at any measured time point (IV). Both Polyquad and BAK induce scattered expression of MUC5AC. The cytotoxicity of BAK-preserved PGA eye drops is higher compared to the safer profile of PF and Polyquad-preserved PGA eye drops (V). Additionally, PF latanoprost does not increase the release of the inflammatory markers interleukin (IL)-6 and IL-8, unlike BAK-preserved latanoprost. A review highlights the active and inactive components of IOP-lowering eye drops (VI). Several preclinical and clinical studies have identified adverse effects of BAK. Although other components, such as the active drug and phosphates, can also cause adverse events, the review clearly states that BAK alone is a major source of decreased tolerability. The conclusion of this thesis is that BAK preservation is unnecessary and harmful to the ocular surface. The preclinical studies demonstrate that GCs die when exposed to BAK. Furthermore, they find that BAK induces a pro-inflammatory response. The review included in the thesis concludes that BAK should be phased out of eye drops for chronic use. Overall, the inclusion of BAK poses a risk of developing DED and poor adherence, which can ultimately lead to disease progression and blindness.

A nerve-goblet cell association promotes allergic conjunctivitis through rapid antigen passage

The penetration of allergens through the epithelial layer is the initial step in the development of allergic conjunctivitis. Although pollinosis patients manifest symptoms within minutes after pollen exposure, the mechanisms of the rapid transport of the allergens remain unclear. In the present study, we found that the instillation of pollen shells rapidly induces a large number of goblet cell-associated antigen passages (GAPs) in the conjunctiva. Antigen acquisition by stromal cells, including macrophages and CD11b+ dendritic cells, correlated with surface GAP formation. Furthermore, a substantial amount of antigen was transported to the stroma during the first 10 minutes of pollen exposure, which was sufficient for the full induction of an allergic conjunctivitis mouse model. This inducible, rapid GAP formation and antigen acquisition were suppressed by topical lidocaine or trigeminal nerve ablation, indicating that the sensory nervous system plays an essential role. Interestingly, pollen shell-stimulated GAP formation was not suppressed by topical atropine, suggesting that the conjunctival GAPs and intestinal GAPs are differentially regulated. These results identify pollen shell-induced GAP as a therapeutic target for allergic conjunctivitis.

A cocktail of small molecules maintains the stemness and differentiation potential of conjunctival epithelial cells

PURPOSE

The conjunctival epithelial cells cultured with bovine serum or feeder cells were not suitable for clinical application. Therefore, we developed a novel serum-free and feeder cell-free culture system containing only a cocktail of three chemicals (3C) to expand the conjunctival epithelial cells.

METHODS

The cell proliferative ability was evaluated by counting, crystal violet staining and Ki67 immunostaining. Co-staining of K7 and MUC5AC was performed to identify goblet cells. PAS staining was used to assess the ability of cells to synthesis and secrete glycoproteins. In vivo, eye drops containing 3C was administered to verify the role of 3C in the mouse conjunctival injury model. PAS, HE and immunofluorescence staining were performed to show conjunctival epithelial repair.

RESULTS

Compared with other small molecule groups and the serum group, the cells in 3C group showed superior morphology and proliferative ability. Meanwhile, 3C maintained the well-proliferative capacity of cells even after fifth passage. The 3C group also exhibited more K7 and MUC5AC double positive cells, and the PAS staining positive areas were present in both the cytoplasm and extracellular matrix. The cell sheets treated with 3C in air-lifted culture were obviously stratified. In vivo, more goblet cells in the conjunctival epithelium were observed in the 3C group.

CONCLUSION

Overall, our culture system can expand the conjunctival epithelial cells and retain their potential to differentiate into mature goblet cells, which provided a promising source of seed cells for conjunctival reconstruction. Furthermore, this system provides new insights for the clinical treatment of ocular surface diseases.

Retinol palmitate in management of chronic Steven-Johnson Syndrome with ocular surface keratinization

PURPOSE

To study the outcomes of topical Retinol Palmitate ophthalmic solution in chronic Stevens-Johnson Syndrome with ocular surface keratinisation.

METHODS

It was a comparative interventional study conducted at Rajendra Prasad Centre for Ophthalmic Sciences, Delhi, India from 2020 to 2022 evaluating outcomes of addition of topical Retinol Palmitate to conventional treatment objectively as well as subjectively from baseline up to 12 weeks.

RESULTS

A statistically significant improvement was seen in patients who received topical Retinol palmitate at 12 weeks in terms of Schirmer-1 test(p=<0.01), tear prism height on ASOCT(p = 0.02), Rose Bengal staining score of cornea(p = 0.01) and conjunctiva (p < 0.01), reduction of ocular surface keratinisation on impression cytology(p = 0.01) and subjective evaluation using OSDI questionnaire(p = 0.04).Impression cytology revealed goblet cells in Retinol palmitate group at 1 week after initiation of therapy, which increased further at 1 month follow up but reduced at 3 months. No goblet cells were seen in control group at any follow-up. No significant difference was noted between the two groups in terms of visual acuity, tear film breakup time, inflammatory cells on impression cytology and inflammatory markers in tears.

CONCLUSION

Topical Retinol palmitate is a safe and effective drug in cases of chronic SJS with ocular surface keratinisation. It has the potential to reverse keratinisation of the ocular surface and promote development of goblet cells. However, the survival of goblet cells is not long lasting.

Experimental study of the mechanism of induction of conjunctival goblet cell hyperexpression using CHIR-99021 in vitro

A component of the tear film, mucin is produced by conjunctival goblet cells and is crucial to preserving the tear film's stability. Severe thermal burns, chemical burns, and severe ocular surface diseases can cause extensive damage to the conjunctiva, destroy the secretory function of goblet cells, and affect the stability of the tear film and integrity of the ocular surface. Currently, the expansion efficiency of goblet cells in vitro is low. In this study, we observed that rabbit conjunctival epithelial cells exhibited dense colony morphology after stimulation with the Wnt/β-catenin signaling pathway activator CHIR-99021 and promoted the differentiation of conjunctival goblet cells and the expression of its specific marker Muc5ac, among which the best induction effect was observed after 72 h in vitro culture with 5 μmol/L CHIR-99021. Under optimal culture conditions, CHIR-99021 increased the expression levels of the Wnt/β-catenin signaling pathway factors Frzb, β-catenin, SAM pointed domain containing ETS transcription factor, and glycogen synthase kinase-3β and the levels of the Notch signaling pathway factors Notch1 and Krüppel-like factor 4 while decreasing the expression levels of Jagged-1 and Hes1. The expression level of ABCG2, a marker of epithelial stem cells, was raised to keep rabbit conjunctival epithelial cells from self-renewing. Our study showed that CHIR-99021 stimulation successfully activated the Wnt/β-catenin signaling pathway and conjunctival goblet cell differentiation was stimulated, in which the Notch signaling pathway played a combined role. Those results provide a novel idea for the expansion of goblet cells in vitro.

Full thickness 3D in vitro conjunctiva model enables goblet cell differentiation

In vitro culture and generation of highly specialized goblet cells is still a major challenge in conjunctival 3D in vitro equivalents. A model comprising all physiological factors, including mucus-secreting goblet cells has the potential to act as a new platform for studies on conjunctival diseases. We isolated primary conjunctival epithelial cells and fibroblasts from human biopsies. 3D models were generated from either epithelial layers or a combination of those with a connective tissue equivalent. Epithelial models were investigated for marker expression and barrier function. Full-thickness models were analyzed for goblet cell morphology and marker expression via immunofluorescence and quantitative real-time PCR. Simple epithelial models cultured at the air-liquid interface showed stratified multi-layer epithelia with pathologic keratinization and without goblet cell formation. The combination with a connective tissue equivalent to generate a full-thickness model led to the formation of a non-keratinized stratified multi-layer epithelium and induced goblet cell differentiation. In our model, a high resemblance to natural conjunctiva was achieved by the combination of conjunctival epithelial cells with fibroblasts embedded in a collagen-hydrogel as connective tissue equivalent. In the future, our conjunctival in vitro equivalent enables the investigation of goblet cell differentiation, conjunctival pathologies as well as drug testing.

Morphological and ultrastructural study of the palpebral conjunctiva of healthy domestic cats

OBJECTIVE

To describe the morphology of the meibomian glands and goblet cells in the palpebral conjunctiva of healthy cats.

ANIMALS STUDIED

Five healthy domestic cats without ocular changes that had died from causes unrelated to the study were evaluated.

PROCEDURES

Forty samples were collected from upper and lower palpebral conjunctiva and 20 from palpebral fornix region in the nasal corner. The samples were processed for scanning electron microscopy (SEM), transmission electron microscopy (TEM), and histopathology.

RESULTS

In the SEM analysis of the palpebral fornix, numerous points of mucous extrusion between the cell junctions were visualized, along with the presence of microvilli in the apical portions with small secretory vesicles. A homogeneous surface was highlighted, formed by the arrangement of cell contours in the form of hexagons. The grouping of goblet cells and their cytoplasmic vesicles filled with homogeneous content was visualized using TEM. Histopathology showed goblet cells interspersed with stratified epithelium accompanied by well-vascularized connective tissue. In the samples stained with hematoxylin and eosin, the meibomian glands, formed by acinar cells and with the presence of individual openings of the ducts in the eyelid margin, were easily visualized in the eyelid margins.

CONCLUSIONS

This study describes the ultrastructural form of goblet cells and the morphology of the palpebral conjunctiva of healthy cats by the histopathology of the meibomian glands. This description can serve as a parameter of normality and aid in the detection of morphological alterations in these structures, as well as a parameter for comparison with other animal species.

The protective role of conjunctival goblet cell mucin sialylation

Gel-forming mucins secreted by conjunctival goblet cells have been implicated in the clearance of allergens, pathogens, and debris. However, their roles remain incompletely understood. Here we show that human and mouse conjunctival goblet cell mucins have Alcian blue-detectable sialic acids, but not sulfates in the steady state. Interestingly, Balb/c mouse strain lacks this sialylation due to a point mutation in a sialyltransferase gene, St6galnac1, which is responsible for sialyl-Tn synthesis. Introduction of intact St6galnac1 to Balb/c restores the sialylation of conjunctival goblet cell mucus. Sialylated mucus efficiently captures and encapsulates the allergen particles in an impenetrable layer, leading to the protection of mice from the development of allergic conjunctivitis. Expression of ST6GALNAC1 and sialyl-Tn is upregulated in humans under conditions with chronic stimuli. These results indicate that the sialylated glycans on the ocular mucins play an essential role in maintaining the conjunctival mucosa by protecting from the incoming foreign bodies such as allergen particles.

Improving ocular bioavailability of hydrophilic drugs through dynamic covalent complexation

The clinical benefits of diquafosol tetrasodium (DQS), a hydrophilic P2Y2 receptor agonist for dry eye, have been hindered by a demanding dosing regimen. Nevertheless, it is challenging to achieve sustained release of DQS with conventional drug delivery vehicles which are mainly designed for hydrophobic small molecule drugs. To address this, we developed an affinity hydrogel for DQS by taking advantage of borate-mediated dynamic covalent complexation between DQS and hydroxypropyl guar. The resultant formulation (3% DQS Gel) was characterized by sustained release, low corneal permeation, and extended ocular retention, which were desirable attributes for ocular surface drug delivery. Both in vitro and in vivo studies had been carried out to verify the biocompatibility of 3% DQS Gel. Using corneal fluorescein staining, the Schirmer's test, PAS staining, quantitative PCR and immunohistological analyses as outcome measures, the superior therapeutic effects of 3% DQS Gel over PBS, the hydrogel vehicle and free DQS were demonstrated in a mouse dry eye model. Our DQS delivery strategy reported herein is readily applicable to other hydrophilic small molecule drugs with cis-diol moieties, thus providing a general solution to improve clinical outcomes of numerous diseases.

The transconjunctival orbitotomy: A versatile approach to the orbit and beyond

In the management of orbital disorders and defects, minimally invasive surgical approaches have become increasingly efficient for their reduction of operative trauma and access without compromise of therapeutic benefit or diagnostic yield. Various approaches have focused on bone- and canthal-sparing techniques and concealed and small skin incisions. We review the current state of knowledge of procedures to enter the orbit via the conjunctiva. Any quadrant of the orbit can be accessed via the conjunctiva. Surgical incisions involve the orbital palpebral, forniceal, and bulbar conjunctiva. According to the location, nature, and size of the lesion, the transconjunctival orbitotomy can be used as a single procedure, in combination with a caruncular approach or as an adjunct in a multidisciplinary procedure for lesions extending deep into or outside the orbit. The working space and field of operating view can be expanded by releasing the horizontal tension of the eyelid with a lateral cantholysis, lateral paracanthal blepharotomy, or medial lid split procedure. Complications related to the conjunctival incision are reduced to dry eye disease.

Suppression of NLRP3/Caspase-1/GSDMD Mediated Corneal Epithelium Pyroptosis Using Melatonin-Loaded Liposomes to Inhibit Benzalkonium Chloride-Induced Dry Eye Disease

Introduction

Benzalkonium chloride (BAC) is widely employed as a preservative in eye drops, which will cause the death of corneal epithelial cells due to ROS production, DNA strand breakage, and mitochondrial dysfunction, resulting in dry eye disease (DED)-like changes in ocular surface tissues. In this study, Melatonin (MT) liposomes (TAT-MT-LIPs) designed by loading MT into TAT-modified liposomes have been developed, characterized, and used for inhibiting BAC-induced DED (BAC-DED).

Methods

The TAT was chemically grafted onto the Mal-PEG₂₀₀₀-DSPE by Michael's addition between the sulfhydryl group in TAT and the maleimide group in Mal-PEG₂₀₀₀-DSPE. TAT-MT-LIPs were prepared using film dispersion followed by the extrusion method and topically treated in rats once a day. BAC-DED was induced in rats by topical administration with 0.2% BAC twice daily. Defects, edema, and inflammation of the corneas, as well as IOP, were examined. Histologic analyses of corneas were performed to assess the change of mitochondrial DNA oxidation and NLRP3/Caspase-1/GSDMD signaling transduction.

Results

After topical administration, TAT-MT-LIPs significantly alleviated DED-clinical symptoms of experimental animals by inhibiting tissue inflammation and preventing the loss of the corneal epithelium and conjunctival goblet cells. Our data suggested continuous ocular surface exposure of BAC-induced NLRP3/Caspase-1/GSDMD mediated corneal epithelium pyroptosis, which was not reported before. BAC caused substantial mt-DNA oxidation, which promoted the transduction of NLRP3/Caspase-1/GSDMD and consequent corneal epithelium pyroptosis. TAT-MT-LIPs could efficiently suppress the BAC-induced corneal epithelium pyroptosis and inflammation by inhibiting mt-DNA oxidation and the subsequent signal transmission.

Conclusion

NLRP3/Caspase-1/GSDMD mediated corneal epithelium pyroptosis is involved in the development of BAC-DED. The present study provided new insights into the adverse effects of BAC, which can serve as a new target for protecting corneal epithelium when applying BAC as a preservative in eye drops. The developed TAT-MT-LIPs can efficiently inhibit BAC-DED and give great potential to be developed as a new DED treatment.

A Single Administration of OC-01 (Varenicline Solution) Nasal Spray Induces Short-Term Alterations in Conjunctival Goblet Cells in Patients with Dry Eye Disease

INTRODUCTION

Dry eye disease is characterized by a persistently unstable or deficient tear film causing discomfort or visual impairment. Varenicline is a small-molecule nicotinic acetylcholine receptor agonist recently approved for use as a preservative-free nasal spray (OC-01 [varenicline solution] nasal spray [OC-01 VNS]) to treat signs and symptoms of dry eye disease, but its effect on conjunctival goblet cells has not been studied.

METHODS

In this phase 2, single-center, vehicle-controlled study, patients aged 18 years or more with a diagnosis of dry eye disease and Ocular Surface Disease Index© score of at least 23 were randomized 2:1 to receive a 50-µL single dose of OC-01 0.06 mg VNS or vehicle nasal spray in each nostril. Image assessments for area and perimeter were performed pre and 10 min post treatment for goblet cells by in vivo confocal microscopy and for meibomian glands by infrared meibography. Non-parametric Wilcoxon signed-rank test compared pre- and post-treatment measurements for each treatment group. Treatment-emergent adverse events (TEAEs) were assessed.

RESULTS

The study randomized 18 patients (mean age 61 years); 6 received vehicle (3/6 [50%] female) and 12 patients received OC-01 VNS (11/12 [92%] female). OC-01 VNS treatment decreased mean goblet cell area (pre-treatment, 106.4 µm2; post-treatment, 67.6 µm2; p = 0.02) and perimeter (pre-treatment, 38.9 µm; post-treatment, 31.2 µm; p = 0.03) but not vehicle did not (p = 0.25). There were no significant changes in mean meibomian gland area with either treatment (p ≥ 0.05). All TEAEs were non-ocular, non-serious, and mild.

CONCLUSIONS

This study demonstrated that a single administration of OC-01 0.06 mg VNS in patients with dry eye disease reduced conjunctival goblet cell area and perimeter, suggesting goblet cell degranulation and associated release of lubricating mucin. By activating the natural tear film, OC-01 VNS may provide benefits over topical medications.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03688802.

The association between visual display terminal use and dry eye: a review

BACKGROUND

Dry eye disease (DED) is a multifactorial disease of the tear film and ocular surface. It causes ocular symptoms, reduced quality of life and a considerable economic burden on society. Prolonged use of visual display terminals (VDTs) has been suggested as an important risk factor for DED.

PURPOSE

This review aims to study the association between DED and VDT use with an emphasis on the prevalence of DED among VDT users and harmful daily duration of VDT use.

METHODS

A PubMed search was conducted and yielded 57 relevant articles based on a set of inclusion and exclusion criteria. The studies were subclassified according to study design.

RESULTS

The far majority of the studies showed an association between VDT use and DED or DED-related signs and symptoms. The prevalence of definite or probable DED in VDT and office workers ranged from 26% to 70%, with as few as 1-2 hr of VDT exposure per day being associated with DED.

CONCLUSION

VDT use is strongly associated with DED. VDT-associated DED is prevalent, but the exact prevalence needs to be further elucidated using standardized DED diagnosis criteria. Furthermore, a safe lower limit of daily VDT use has yet to be established. More research is needed on the effect of digitalization and digital transformation, which are particularly high during the time of the COVID-19 pandemic.

Viscoelastic properties of the human tear film

When considering eye blinking from a tribological perspective, tear viscosity is expected to play a fundamental role. The application of rheological techniques to describe the tear film dates back to the late 1980s, but there has been a continuous need of reappraisal due to new findings in tear film biochemistry and to the development of new methods of physico-chemical characterization. This review provides an overview on tear rheological behavior by analyzing the peer-reviewed literature on this topic. Specifically, examples of in-vitro and in-vivo viscosity measurements are detailed, highlighting experimental criticalities and the need of a standard convention for rheological techniques to compare data across different studies, of analyses on tears of single individuals even within the limits of the low volume available, and of a further development of in-vivo techniques. Then, the controversial role of specific tear components on viscosity is discussed, together with the alterations associated to dry eye disease and contact lens wear. Finally, an updated focus is reported on the viscosity of artificial tears formulations.

Immune regulation of the ocular surface

Despite constant exposure to various environmental stimuli, the ocular surface remains intact and uninflamed while maintaining the transparency of the cornea and its visual function. This 'immune privilege' of the ocular surface is not simply a result of the physical barrier function of the mucosal lining but, more importantly, is actively maintained through a variety of immunoregulatory mechanisms that prevent the disruption of immune homeostasis. In this review, we focus on essential molecular and cellular players that promote immune quiescence in steady-state conditions and suppress inflammation in disease-states. Specifically, we examine the interactions between the ocular surface and its local draining lymphoid compartment, by encompassing the corneal epithelium, corneal nerves and cornea-resident myeloid cells, conjunctival goblet cells, and regulatory T cells (Treg) in the context of ocular surface autoimmune inflammation (dry eye disease) and alloimmunity (corneal transplantation). A better understanding of the immunoregulatory mechanisms will facilitate the development of novel, targeted immunomodulatory strategies for a broad range of ocular surface inflammatory disorders.

Selenium and the 15kDa Selenoprotein Impact Colorectal Tumorigenesis by Modulating Intestinal Barrier Integrity

Selenoproteins play important roles in many cellular functions and biochemical pathways in mammals. Our previous study showed that the deficiency of the 15 kDa selenoprotein (Selenof) significantly reduced the formation of aberrant crypt foci (ACF) in a mouse model of azoxymethane (AOM)-induced colon carcinogenesis. The objective of this study was to examine the effects of Selenof on inflammatory tumorigenesis, and whether dietary selenium modified these effects. For 20 weeks post-weaning, Selenof-knockout (KO) mice and littermate controls were fed diets that were either deficient, adequate or high in sodium selenite. Colon tumors were induced with AOM and dextran sulfate sodium. Surprisingly, KO mice had drastically fewer ACF but developed a similar number of tumors as their littermate controls. Expression of genes important in inflammatory colorectal cancer and those relevant to epithelial barrier function was assessed, in addition to structural differences via tissue histology. Our findings point to Selenof's potential role in intestinal barrier integrity and structural changes in glandular and mucin-producing goblet cells in the mucosa and submucosa, which may determine the type of tumor developing.

Characterisation of Gel-Forming Mucins Produced In Vivo and In Ex Vivo Conjunctival Explant Cultures

One key element to the health of the ocular surface encompasses the presence of gel-forming mucins in the pre-ocular tear film. Conjunctival goblet cells are specialized epithelial cells that secrete mucins necessary for tear film stability and general homeostasis. Their dysfunction can be linked to a range of ocular surface inflammation disorders and chronic injuries. To obtain new perspectives and angles to tackle mucin deficiency, the need for an accurate evaluation of their presence and corresponding mucin secretion in ex vivo conjunctival cultures has become a requisite. In vitro, goblet cells show a significant decrease in the production and secretion of gel-forming mucins, accompanied by signs of dedifferentiation or transdifferentiation. Explant cultures on laminin-treated CLP-PEG hydrogels can, however, support the production of gel-forming mucins. Together, we challenge the current paradigm to evaluate the presence of cultured goblet cells solely based on their general mucin (MUC) content through imaging analyses, showing the need for additional techniques to assess the functionality of goblet cells. In addition, we broadened the gel-forming mucin profile of in vivo goblet cells with MUC5B and MUC6, while MUC2 and MUC6 is added to the profile of cultured goblet cells.

Goblet Cell Differentiation Potential in Human Corneal Limbal Epithelial Progenitor Cells In Vitro

Purpose

The existence of goblet cells has been regarded as a critical differential point to distinguish conjunctival epithelium from corneal epithelium in vivo. We tested differentiation potential of single progenitor cells from corneal limbal epithelium with growth factors in vitro.

Methods

Dissociated single cells from corneal limbal epithelium were cultured in the serum- and feeder cell–free medium containing B27 and various growth factors using nontissue culture dishes. Specific marker expression was examined in the colonies stimulated with growth factors. Differentiation of some mucosal epithelia was tested.

Results

Adherent single cells from dissociated single cells in corneal limbal epithelium did not proliferate in the serum- and feeder cell–free medium containing B27 only and formed corneal epithelium with B27 plus epidermal growth factor, while they gave rise to goblet cell with periodic acid Schiff–positive mucin and cytokeratin-3 and-12 expressing corneal epithelium with fibroblast growth factor (FGF)2 stimulation. Colonies stimulated with FGF2 expressed goblet cell specific MUC5AC and cytokeratin-7 mRNA and protein. FGF receptor 1 was a functional receptor for the differentiation to goblet cells and corneal epithelium.

Conclusions

Single corneal limbal progenitor cells give rise to goblet cells and corneal epithelium by FGF2 stimulation via FGF receptor 1 in vitro.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

Dry eye in rheumatoid arthritis patients under TNF-inhibitors: conjunctival goblet cell as an early ocular biomarker

Dry eye disease (DED) is common in Rheumatoid Arthritis (RA) patients. The application of conjunctival goblet cell count as a clinical biomarker to diagnose and respond to treatment can take place in rheumatoid arthritis patients under TNF-inhibitors (TNFi) therapy. This study aimed to investigate the ocular surface parameters and the long-term effects of TNFi therapy on ocular surface features and goblet cell count of rheumatoid arthritis patients. At baseline, rheumatoid arthritis patients eligible to TNFi were compared to healthy controls (similar age/gender), regarding Ocular Surface Disease Index (OSDI) questionnaire, Schirmer I test, tear break-up time test, vital dye staining of the ocular surface, and conjunctival impression cytology. DED severity grade, impression cytology score, and goblet cell count were analyzed. Rheumatoid arthritis patients were followed after three (3 M) and 12 months (12 M), during TNFi treatment. Sixteen rheumatoid arthritis patients and 24 controls were compared: a higher frequency of abnormal OSDI (68.8% vs. 16.7%, p = 0.002), Schirmer's test < 10 mm (37.5% vs. 8.3%, p = 0.042), meibomian gland dysfunction (50% vs. 8.3%, p = 0.007), abnormal impression cytology (75% vs. 8.3%, p < 0.001), and mild to moderate DED (81.3% vs. 4.2%, p < 0.001) were observed in rheumatoid arthritis patients, who also had lower goblet cell count [325 (274-707) cells/mm² vs. 742 (562-863) cells/mm², p = 0.004]. The presence of Meibomian gland dysfunction was associated with higher disease activity scores (p < 0.05). The prospective early observation of these patients at 3 M showed an increase improvement in tear production by Schirmer's test [13 (7.5-17.5) vs. 23.5 (16-35); p = 0.001], and an improvement in impression cytology score [1 (0.5-2) vs. 1 (0-1), p = 0.031] and in goblet cell count [325 (274-707) vs. 931 (656-1,244), p < 0.001]. Eight RA responders to TNFi were also re-evaluated at 12 M with further improvement in goblet cell count [393 (275-827) vs. 872 (502-1,185) vs. 1,079 (867-1,244), p = 0.047]. Multifactorial DED is frequent in RA patients, comprising aqueous, lipid, and mucin components. TNFi prompt improves tear production and recovers the goblet cells, which can be a biomarker of the pathological process and response to therapy in this population.