Role of Matrix Metalloproteinase 9 in Ocular Surface Disorders

Restoration of corneal epithelial barrier function: A possible target for corneal neovascularization

Corneal neovascularization (CoNV) is the second leading common cause of vision impairment worldwide and is a blinding pathological alteration brought on by ocular trauma, infection, and other factors. There are some limitations in the treatment of CoNV, hence it's critical to look into novel therapeutic targets. The corneal epithelial barrier, which is the initial barrier of the ocular surface, is an important structure that shields the eye from changes in the internal environment or invasion by the external environment. This study sought to collate evidence on the regulation of corneal epithelial barrier injury on the activation of vascular endothelial cells (VECs), basement membrane (BM) degradation, differentiation, migration, and proliferation of VECs, vascular maturation and stability, and other key processes in CoNV, so as to provide a novel concept for CoNV therapy targeting corneal epithelial barrier repair.

Probiotic LB101 alleviates dry eye in mice by suppressing matrix metalloproteinase-9 expression through the regulation of gut microbiota-involved NF-κB signaling

Tear matrix metalloproteinase (MMP)-9 is an inflammatory signal in patients with dry eye (DE). In the present study, to understand the action mechanism of probiotic LB101 (Lactobacillus plantarum NK151 and Bifidobacterium bifidum NK175 [4:1] mix) against DE, we investigated its effect on tear amount and inflammatory marker expression levels in mice with unilateral exorbital lacrimal gland excision/atropine-benzalkonium chloride application (EB) or fecal microbiota transplantation from mice with EB (eFMT). Oral gavage of LB101 increased EB-suppressed tear amount and decreased EB-induced blinking number. Furthermore, LB101 decreased EB-induced TNF-α, IL-1β, and MMP-9 expression, TNF-α+ and NF-κB+CD11c+ cell populations, and edema in the conjunctiva, while EB-suppressed IL-10 and occludin expression increased. LB101 also decreased EB-induced TNF-α and IL-1β expression and NF-κB+CD11c+ cell population in the colon. eFMT also decreased tear amount and increased blinking number in the transplanted mice. eFMT increased TNF-α, IL-1β, and MMP-9 expression and TNF-α+ and NF-κB+CD11c+ cell populations in the conjunctiva and TNF-α and IL-1β expression and NF-κB+CD11c+ cell populations in the colon. Oral gavage of LB101 increased eFMT-suppressed tear amount and decreased eFMT-induced blinking number. Furthermore, LB101 decreased TNF-α, IL-1β, and MMP-9 expression, TNF-α+ and NF-κB+CD11c+ cell populations, and edema in the conjunctiva and TNF-α and IL-1β expression and NF-κB+CD11c+ cell population in the colon, while eFMT-suppressed IL-10 and occludin expression decreased. Furthermore, LB101 increased eFMT-suppressed Muribaculaceae, Prevotellaceae, and Lactobacillaceae populations in the gut microbiota, while eFMT-induced Bacteroidaceae population decreased. These findings suggest that DE may cause gut dysbiosis, which may be a risk factor for DE, and LB101 may alleviate DE with gut inflammation by suppressing the expression of MMP-9 and proinflammatory cytokines TNF-α and IL-1β with the regulation of gut microbiota-involved NF-κB signaling.

Debulking corneal biopsy with tectonic amniotic membrane transplantation in refractory clinically presumed fungal keratitis

The treatment of fungal keratitis (FK) is challenging due to the subacute indolent course, and initial misdiagnosis. In this retrospective case series, we highlight both the diagnostic and therapeutic roles of corneal biopsy together with amniotic membrane transplantation (AMT) in patients with refractory clinically presumed FK. Debulking biopsy and tectonic AMT were performed during the initial presentation. Biopsy specimens were sent for KOH smears and cultures. After KOH smears confirmed the presence of fungal elements, topical voriconazole 1% was prescribed for the first 72 h then tailored according to the clinical response and the culture results. The outcome measures were complete resolution of infection and restoration of corneal integrity. Cases associated with culture proven bacterial keratitis were excluded. Twelve cases were included in the study. KOH smears confirmed the presence of fungal growth in all specimens. Cultures grew Aspergillus in 6/12 cases, sensitive to voriconazole (5/6) and amphotericin (3/6); Fusarium (4/12), sensitive to both voriconazole and amphotericin; and no growth in 2/12 cases. Amphotericin 0.15% eye drops were added to the 7 cases with proven sensitivity and to the remaining 2 culture negative cases. Gradual resolution of infection was seen in all cases after 35.6 ± 7.8 days. In FK, a debulking biopsy simultaneously with AMT help decrease the microbial load, suppress the inflammatory process, support the corneal integrity, confirm the presence of fungal pathogen.

Comparative Proteomics Reveals Prolonged Corneal Preservation Impaired Ocular Surface Immunity Accompanied by Fibrosis in Human Stroma

Cornea transplantation is one of the most commonly performed allotransplantations worldwide. Prolonged storage of donor corneas leads to decreased endothelial cell viability, severe stromal edema, and opacification, significantly compromising the success rate of corneal transplantation. Corneal stroma, which constitutes the majority of the cornea, plays a crucial role in maintaining its shape and transparency. In this study, we conducted proteomic analysis of corneal stroma preserved in Optisol-GS medium at 4 °C for 7 or 14 days to investigate molecular changes during storage. Among 1923 identified proteins, 1634 were quantifiable and 387 were significantly regulated with longer preservation. Compared to stroma preserved for 7 days, proteins involved in ocular surface immunomodulation were largely downregulated while proteins associated with extracellular matrix reorganization and fibrosis were upregulated in those preserved for 14 days. The increase in extracellular matrix structural proteins together with upregulation of growth factor signaling implies the occurrence of stromal fibrosis, which may compromise tissue clarity and cause vision impairments. This study is the first to provide insights into how storage duration affects corneal stroma from a proteomic perspective. Our findings may contribute to future research efforts aimed at developing long-term preservation techniques and improving the quality of preserved corneas, thus maximizing their clinical application.

The Utilization of Glucagon-like Peptide 1 Agonists and Risk of Following External Eye Diseases in Type 2 Diabetes Mellitus Individuals: A Population-Based Study

The glucagon-like peptide 1 (GLP-1) agonist showed anti-hyperglycemic and anti-inflammatory effects, which may retard the risk of external eye disease. The protective effect of GLP-1 agonist and dry eye disease (DED) was found, while the relationship between GLP-1 agonist and other corneal diseases was not clear. Herein, we aim to evaluate the association between the usage of GLP-1 agonists and the development of the following external eye disease in type 2 diabetes mellitus (T2DM) patients. A retrospective cohort study using the National Health Insurance Research Database (NHIRD) of Taiwan was conducted. The T2DM patients were divided into those with GLP-1 treatment and those without GLP-1 treatment and matched with a 1:2 ratio. The main outcomes were the development of dry eye disease (DED), superficial keratitis, and infectious keratitis. The Cox proportional hazard regression was adopted to produce the adjusted hazard ratio (aHR) with a 95% confidence interval (CI) of external eye diseases between groups. There were 115, 54, and 11 episodes of DED, superficial keratitis, and infectious keratitis in the GLP-1 group. Another 280, 168, and 31 events of DED, superficial keratitis, and infectious keratitis were recorded in the control group. The GLP-1 group demonstrated a significantly lower incidence of DED (aHR: 0.853, 95% CI: 0.668-0.989, p = 0.0356) and superficial keratitis (aHR: 0.670, 95% CI: 0.475-0.945, p = 0.0107) compared to the control group. In the subgroup analyses, the correlation of GLP-1 agonist and DED development was more prominent in patients younger than 60 years old (p = 0.0018). In conclusion, the GLP-1 agonist treatments are significantly associated with a lower incidence of subsequent DED and superficial keratitis, while the relationship was not significant between GLP-1 agonist usage and infectious keratitis.

Ocular surface inflammation and ectatic corneal disorders

PURPOSE OF REVIEW

Inflammatory mediators are a focus of recent corneal ectasia (CE) research and are a profound, modifiable contributor to CE in general and keratoconus (KC) in particular, opening a path to explore new methods of control. As advanced imaging technology and expanded population screening allow for earlier detection, the possibility of early intervention can profoundly change the prognosis of CE.

RECENT FINDINGS

Significant increases in the inflammatory mediators and immune components have been observed in the cornea, tear fluid, and blood of ectasia patients, while inflammation dampeners such as vitamin D and their receptors are reduced. Atopy and allergy have a strong association with KC, known to increase itch factors and stimulate eye rubbing, a risk factor in ectasia pathogenesis. Management of atopy or allergic conditions and topical anti-inflammatories has helped stabilize CE disease.

SUMMARY

Strategies such as monitoring inflammatory factors and using immune or inflammatory modulators, including managing subclinical inflammation, may be clinically beneficial in stabilizing the disease and improving outcomes. The detected factors are biomarkers, but as yet unproven to be sensitive or specific enough to be considered biomarkers for early detection of CE. The establishment of such biomarkers could improve the therapeutic outcome.

The role of matrix metalloproteinases in infectious corneal ulcers

During infectious keratitis, the production of collagenolytic and inflammatory substances, along with increased corneal matrix metalloproteinase (MMP) activity, induces the degradation of corneal collagen and may cause postkeratitis complications, such as opacity, thinning, and corneal perforation. MMPs, especially MMP-2 and MMP-9, are overexpressed in infectious keratitis and sustained over time by inflammatory and nonmicrobial mechanisms. The high MMP levels are correlated with excessive corneal destruction in bacterial, herpetic, fungal, and acanthamoeba infections. Nonspecific treatments, such as tetracyclines, particularly doxycycline, or corticosteroids, are used as adjuvants to antimicrobials to alleviate the disproportionate degradation and inflammation of the corneal layers caused by corneal MMPs and decrease the recruitment and infiltration of inflammatory cells. Treatments showing inhibition of specific MMPs (Galardin, ZHAWOC7726), interfering with pro-MMP activation (EDTA, ascorbic acid), or showing anticytokine effect (epigallocatechin-2-gallate, TRAM-34) have been reported. Other treatments show a direct action over corneal collagen structure such as corneal cross-linking or have been associated with reduction of MMP levels such as amniotic membrane grafting. Although the use of these drugs has been shown in studies to be effective in controlling inflammation, especially in experimental ones, robust studies are still needed based on randomized and randomized clinical trials to demonstrate their potential effect as adjuvants in the management of infectious keratitis.

Diagnosis of Photokeratitis by Tear Ferning Using a Novel Set of SK Grading Criteria in a UVB-Induced Mouse Model

Purpose

Current ocular surface diagnostic methods may not totally meet and implement the clinical demands for early and precise treatments. The tear ferning (TF) test has been known as a quick, simple, and inexpensive procedure. This study aimed to validate the TF test as an alternative method for early determination of photokeratitis status.

Methods

The tear sample was collected from the UVB-induced photokeratitis eyes and processed for TF formation. The TF patterns were graded by both the Masmali and a Sophie-Kevin (SK) grading criteria, a new set of criteria modified from the Masmali grading, for differential diagnoses. In addition, the TF test results were correlated with three clinical ocular surface indicators, including tear volume (TV), tear film break-up time (TBUT), and cornea staining, to evaluate the diagnostic capacity.

Results

Differential diagnosis between the normal and the photokeratitis status was achieved by the TF test. The SK grading reflected earlier photokeratitis status than the Masmali grading criteria. The TF results were strongly correlated with the three clinical ocular surface indicators, particularly for the TBUT and cornea staining.

Conclusions

The TF test was proven to have a capacity to distinguish photokeratitis from the normal status at an early stage by using the SK grading criteria. It is therefore potentially useful for photokeratitis diagnosis in the clinical settings.

Translational Relevance

The TF test may fulfill the demands of precise and early diagnosis to facilitate in time the intervention for photokeratitis.

Collagen membrane loaded with doxycycline through hydroxypropyl chitosan microspheres for the early reconstruction of alkali-burned cornea

Corneal alkali burn is one of the most devastating ophthalmic emergencies correlated with remarkable morbidity resulting in severe visual impairment. Appropriate intervention in the acute phase determines the eventual outcome for later corneal restoration treatment. Since the epithelium plays an essential role in inhibiting inflammation and promoting tissue repair, sustained anti-matrix metalloproteinases (MMPs) and pro-epithelialization are the prior remedies during the first week. In this study, a drug-loaded collagen membrane (Dox-HCM/Col) that could be sutured to overlay the burned cornea was developed to accelerate the early reconstruction. Doxycycline (Dox), a specific inhibitor of MMPs, was encapsulated in collagen membrane (Col) through hydroxypropyl chitosan microspheres (HCM) to develop Dox-HCM/Col, affording a preferable pro-epithelialization microenvironment and an in-situ controlled release. Results showed that loading HCM into Col prolonged the release time to 7 days, and Dox-HCM/Col could significantly suppress the expression of MMP-9 and -13 in vitro and in vivo. Furthermore, the membrane accelerated the corneal complete re-epithelialization and promoted early reconstruction within the first week. Overall, Dox-HCM/Col was a promising biomaterial membrane for treating alkali-burned cornea in the early stage, and our attempt may provide a clinically feasible method for the ocular surface reconstruction.

Epigenetic Activation of Circadian Clock Genes Elicits Inflammation in Experimental Murine Dry Eye

PURPOSE

To explore whether circadian clock genes contribute to elicit inflammation in experimental dry eye (EDE).

METHODS

RNA sequencing analyzed mRNA expression patterns in EDE model. RT-qPCR and/or Western blot determined the expression of inflammatory factors and circadian genes during EDE. MethylTarget™ assays determined the promoter methylation levels of Per genes in vivo. Per2 or Per3 knockdown assessed their effects on inflammatory factors in vitro.

RESULTS

We utilized an intelligently controlled environmental system (ICES) to establish a mouse EDE model. The significant upregulated genes were enriched for circadian rhythms. Therein lied oscillatory and time-dependent upregulation of PER2 and PER3, as well as their promoter hypomethylation during EDE. Silencing PER2 or PER3 significantly decreased inflammatory factor expression and also reversed such increased inflammatory response in azacitidine (AZA) treatment in vitro model.

CONCLUSIONS

Our findings suggest that DNA methylation mediated the upregulation of PER2 and PER3, leading to inflammatory response in EDE.

In Silico and In Vitro Approach for Validating the Inhibition of Matrix Metalloproteinase-9 by Quercetin

PURPOSE

To validate the mechanism and inhibitory activity of quercetin against matrix metalloproteinase-9 (MMP-9) using a hybrid in silico and in vitro approach.

METHODS

The structure of MMP-9 was obtained from the Protein Data Bank, and the active site was identified using previous annotations from the Universal Protein Resource. The structure of quercetin was obtained from ZINC15. Molecular docking was performed to quantify the binding affinity of quercetin to the active site of MMP-9. The inhibitory effect of various concentrations of quercetin (0.0025, 0.025, 0.25, 1.0, and 1.5 mM) on MMP-9 was quantified using a commercially available fluorometric assay. The cytotoxicity of quercetin to immortalized human corneal epithelial cells (HCECs) was quantified by obtaining the metabolic activities of the cells exposed to various concentrations of quercetin for 24 hr.

RESULTS

Quercetin interacts with MMP-9 by binding within the active site pocket and interacting with residues LEU 188, ALA 189, GLU 227, and MET 247. The binding affinity predicted by molecular docking was -9.9 kcal/mol. All concentrations of quercetin demonstrated significant inhibition of MMP-9 enzyme activity (all P <0.03). There was little to no reduction of HCEC metabolic activity after a 24-hr exposure to all concentrations of quercetin ( P >0.99).

CONCLUSIONS

Quercetin inhibited MMP-9 in a dose-dependent manner and was well-tolerated by HCECs, suggesting a potential role in therapy for diseases with upregulated MMP-9 as part of its pathogenesis.

A Pilot Study to Evaluate Genipin in Staphylococcus aureus and Pseudomonas aeruginosa Keratitis Models: Modulation of Pro-Inflammatory Cytokines and Matrix Metalloproteinases

Infectious keratitis is a vision-threatening microbial infection. The increasing antimicrobial resistance and the fact that severe cases often evolve into corneal perforation necessitate the development of alternative therapeutics for effective medical management. Genipin, a natural crosslinker, was recently shown to exert antimicrobial effects in an ex vivo model of microbial keratitis, highlighting its potential to serve as a novel treatment for infectious keratitis. This study aimed to evaluate the antimicrobial and anti-inflammatory effects of genipin in an in vivo model of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) keratitis. Clinical scores, confocal microscopy, plate count, and histology were carried out to evaluate the severity of keratitis. To assess the effect of genipin on inflammation, the gene expression of pro- and anti-inflammatory factors, including matrix metalloproteinases (MMPs), were evaluated. Genipin treatment alleviated the severity of bacterial keratitis by reducing bacterial load and repressing neutrophil infiltration. The expression of interleukin 1B (IL1B), interleukin 6 (IL6), interleukin 8 (IL8), interleukin 15 (IL15), tumor necrosis factor-α (TNF-α), and interferon γ (IFNγ), as well as MMP2 and MMP9, were significantly reduced in genipin-treated corneas. Genipin promoted corneal proteolysis and host resistance to S. aureus and P. aeruginosa infection by suppressing inflammatory cell infiltration, regulating inflammatory mediators, and downregulating the expression of MMP2 and MMP9.

A Pilot Study of a Panel of Ocular Inflammation Biomarkers in Patients with Primary Sjögren’s Syndrome

Ocular diseases have a strong impact on individuals, the effects of which extend from milder visual impairment to blindness. Due to this and to their prevalence, these conditions constitute important health, social and economic challenges. Thus, improvements in their early detection and diagnosis will help dampen the impact of these conditions, both on patients and on healthcare systems alike. In this sense, identifying tear biomarkers could establish better non-invasive approaches to diagnose these diseases and to monitor responses to therapy. With this in mind, we developed a solid phase capture assay, based on antibody microarrays, to quantify S100A6, MMP-9 and CST4 in human tear samples, and we used these arrays to study tear samples from healthy controls and patients with Sjögren’s Syndrome, at times concomitant with rheumatoid arthritis. Our results point out that the detection of S100A6 in tear samples seems to be positively correlated to rheumatoid arthritis, consistent with the systemic nature of this autoinflammatory pathology. Thus, we provide evidence that antibody microarrays may potentially help diagnose certain pathologies, possibly paving the way for significant improvements in the future care of these patients.

Evaluation of delaying effects of different short-term dosage regimens of topical ciprofloxacin on corneal ulcer healing in an avian model

BACKGROUND

Knowledge on possible delaying effects of topical ciprofloxacin on corneal ulcer healing is scarce in avian patients.

OBJECTIVES

The study evaluates effects of different dosage regimens of topical ciprofloxacin on healing of corneal ulcer in an avian model.

METHODS

One hundred and fifty adult layers were randomly allocated into two equal categories each consisted of 5 groups (n = 15): 1, negative control (NC, normal cornea); 2, positive control (PC) (birds with experimental corneal ulcer); and 3, 4 and 5, birds with corneal injury that received ciprofloxacin 0.3% topically q6h, q8h and q12h, respectively for 3 (category 1) or 5 days (category 2). Corneas were excised for histopathological evaluation and determination of MMP-9 expression.

RESULTS

While no significant difference was observed in daily-measured fluorescein-stained ulcer size among ciprofloxacin-treated birds and PC group in category 1, birds in PC group of category 2 had significantly smaller ulcers as compared to antibiotic-treated birds at the end of experiment (p < 0.01 for all cases). Histopathological evaluations at the end of the experiment showed no significant difference among PC and ciprofloxacin-treated birds of both categories for almost all of the assayed parameters. Over expression of MMP-9 mRNA was observed in PC group after 3 and 5 days of ulcer induction compared to NC groups. Its expression in ciprofloxacin-treated birds of both categories remained close to PC groups.

CONCLUSIONS

While ciprofloxacin administration for 3 days does not affect ulcer healing, it delays healing process at the end of 5 days of treatments in an avian model of corneal ulcer injury. This delaying effect is not associated with a drastic change in MMP-9 expression.

Ocular Surface Disease in Glaucoma Patients

PURPOSE

To review the most recent studies in the literature regarding the ocular surface in glaucoma patients and treatment options aimed to reduce ocular surface disease in this population.

METHODS

We performed a literature search in the electronic databases of PubMed CENT RAL, Google Scholar, EMBASE the Register of Controlled Trials, and Ovid MEDLINE using the following terms: "ocular surface", "dry eye", "glaucoma", "selective laser trabeculoplasty", "glaucoma surgery", "preservatives", "preservative free", "ocular surface disease index", "tear break up time", "MMP-9" and "conjunctival hyperemia".

RESULTS

Over the last several years, several studies have demonstrated the changes to the ocular surface in the setting of glaucoma, the best tests for markers of dry eye, and how management can be altered to help address ocular surface disease routinely or in preparation for glaucoma surgery.

CONCLUSION

Ocular surface disease in the glaucoma patient population is widely recognized. It should be addressed to maximize patient compliance and quality of life.

Enzyme-triggered smart antimicrobial drug release systems against bacterial infections

The rapid emergence and spread of drug-resistant bacteria, as one of the most pressing public health threats, are declining our arsenal of available antimicrobial drugs. Advanced antimicrobial drug delivery systems that can achieve precise and controlled release of antimicrobial agents in the microenvironment of bacterial infections will retard the development of antimicrobial resistance. A variety of extracellular enzymes are secreted by bacteria to destroy physical integrity of tissue during their invasion of host body, which can be utilized as stimuli to trigger "on-demand" release of antimicrobials. In the past decade, such bacterial enzyme responsive drug release systems have been intensively studied but few review has been released. Herein, we systematically summarize the recent progress of smart antimicrobial drug delivery systems triggered by bacteria secreted enzymes such as lipase, hyaluronidase, protease and antibiotic degrading enzymes. The perspectives and existing key issues of this field will also be discussed to fuel the innovative research and translational application in the future.

Tear matrix metalloproteinase-9 levels may help to follow a ocular surface injury in lagophthalmic eyes

The preocular tear film is critically important for maintaining healthy ocular surface. In lagophthalmos, increased evaporation and tear film instability can occur. The level of tear matrix metalloproteinase 9 (MMP-9) is considered as a possible marker of ocular surface damage and inflammation. The aim of this study was to evaluate the possible usefulness of measuring tear film levels of MMP-9 in patients with lagophthalmos. Sixteen adult patients with unilateral lagophthalmos due to cerebellopontine angle mass surgery were included. Basic clinical examination including tear film osmolarity, degree of lagophthalmos, ocular surface sensitivity testing, corneal fluorescein staining, and tear break-up time (TBUT) were performed. Furthermore, tear MMP-9 quantification was performed and the values from lagophthalmic and contralateral healthy eye were compared. Possible correlations between tear MMP-9 levels and other parameters were analyzed. The Oxford score was higher in lagophthalmic eyes in comparison to healthy eyes. TBUT and corneal sensitivity were lower in lagophthalmic eyes. There was no difference in osmolarity between the two groups. Tear MMP-9 values were higher in lagophthalmic eyes. A higher MMP-9 value was associated with an increase in ocular surface fluorescein staining and a decrease of TBUT in lagophthalmic eyes. Tear MMP-9 may be used for monitoring ocular surface damage, contribute to early detection of inflammation progression and facilitate treatment adjustments.

Research Progress and Potential Applications of Spermidine in Ocular Diseases

Spermidine, a natural polyamine, exists in almost all human tissues, exhibiting broad properties like anti-aging, autophagy induction, anti-inflammation, anti-oxidation, cell proliferation activation, and ion channel regulation. Considering that spermidine is already present in human nutrition, recent studies targeting supplementing exogenous sources of this polyamine appear feasible. The protective role of spermidine in various systems has been illuminated in the literature, while recent progress of spermidine administration in ocular diseases remains to be clarified. This study shows the current landscape of studies on spermidine and its potential to become a promising therapeutic agent to treat ocular diseases: glaucoma, optic nerve injury, age-related macular degeneration (AMD), cataracts, dry eye syndrome, and bacterial keratitis. It also has the potential to become a potent biomarker to predict keratoconus (KC), cataracts, uveitis, glaucoma, proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and retinopathy of prematurity (ROP). We also summarize the routes of administration and the effects of spermidine at different doses.

MiRNA 24-3p-rich exosomes functionalized DEGMA-modified hyaluronic acid hydrogels for corneal epithelial healing

The damage of corneal epithelium may lead to the formation of irreversible corneal opacities and even blindness. The migration rate of corneal epithelial cells directly affects corneal repair. Here, we explored ocu-microRNA 24-3p (miRNA 24-3p) that can promote rabbit corneal epithelial cells migration and cornea repair. Exosomes, an excellent transport carrier, were exacted from adipose derived mesenchymal stem cells for loading with miRNA 24-3p to prepare miRNA 24-3p-rich exosomes (Exos-miRNA 24-3p). It can accelerate corneal epithelial migration in vitro and in vivo. For application in cornea alkali burns, we further modified hyaluronic acid with di(ethylene glycol) monomethyl ether methacrylate (DEGMA) to obtain a thermosensitive hydrogel, also reported a thermosensitive DEGMA-modified hyaluronic acid hydrogel (THH) for the controlled release of Exos-miRNA 24-3p. It formed a highly uniform and clear thin layer on the ocular surface to resist clearance from blinking and extended the drug-ocular-epithelium contact time. The use of THH-3/Exos-miRNA 24-3p for 28 days after alkali burn injury accelerated corneal epithelial defect healing and epithelial maturation. It also reduced corneal stromal fibrosis and macrophage activation. MiRNA 24-3p-rich exosomes functionalized DEGMA-modified hyaluronic acid hydrogel as a multilevel delivery strategy has a potential use for cell-free therapy of corneal epithelial regeneration.

Elevation of Tear MMP-9 Concentration as a Biomarker of Inflammation in Ocular Pathology by Antibody Microarray Immunodetection Assays

Matrix metalloproteinases are a family of enzymes fundamental in inflammatory processes. Between them, MMP-9 is up-regulated during inflammation; thus, its quantification in non-invasive fluids is a promising approach for inflammation identification. To this goal, a biomarker quantification test was developed for ocular inflammation detection using anti-MMP-9 antibody microarrays (AbMAs). After validation with eight healthy control tear samples characterized by ELISA, 20 samples were tested from individuals diagnosed with ocular inflammation due to: cataracts, glaucoma, meibomian gland dysfunction, allergy, or dry eye. Concentration values of tear MMP-9 were obtained for each sample, and 12 patients surpassed the pathological threshold (30 ng/mL). A significant elevation of MMP-9 concentration in the tears of glaucoma patients compared with healthy controls was observed. In order to evaluate the diagnostic ability, an ROC curve analysis was performed using our data, determining the optimal threshold for the test at 33.6 ng/mL of tear MMP-9. In addition, a confusion matrix was applied, estimating sensitivity at 60%, specificity at 88%, and accuracy at 68%. In conclusion, we demonstrated that the AbMAs system allows the quantification of MMP-9 in pathologies that involve inflammation of the ocular surface.

The Role of Metalloproteinases and Their Tissue Inhibitors on Ocular Diseases: Focusing on Potential Mechanisms

Eye diseases are associated with visual impairment, reduced quality of life, and may even lead to vision loss. The efficacy of available treatment of eye diseases is not satisfactory. The unique environment of the eye related to anatomical and physiological barriers and constraints limits the bioavailability of existing agents. In turn, complex ethiopathogenesis of ocular disorders that used drugs generally are non-disease specific and do not act causally. Therefore, there is a need for the development of a new therapeutic and preventive approach. It seems that matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) have a significant role in the development and progression of eye diseases and could be used in the therapy of these disorders as pharmacological targets. MMPs and TIMPs play an important role in the angiogenesis, epithelial-mesenchymal transition, cell invasion, and migration, which occur in ocular diseases. In this review, we aim to describe the participation of MMPs and TIMPs in the eye diseases, such as age-related macular degeneration, cataract, diabetic retinopathy, dry eye syndrome, glaucoma, and ocular cancers, posterior capsule opacification focusing on potential mechanisms.

Therapeutic Effects of Topical Application of Lycium barbarum Polysaccharide in a Murine Model of Dry Eye

Purpose

To evaluate the safety and efficacy of Lycium barbarum polysaccharide (LBP) eye drops in a murine model of dry eye disease (DED).

Methods

Six- to eight-week-old female C57BL/6 mice were subjected to a combination of desiccating stress (DS) and topical benzalkonium chloride (BAC) to induce DED. Five microliters of LBP eye drops (0.625, 2.5, or 12.5 mg/ml) or PBS was applied topically 3 times per day for 10 days to subsequently test their efficacy. Tear secretion, tear breakup time (TBUT), corneal irregularity, and corneal fluorescein staining scores were measured on days 3 and 10 after treatment. The expression of tumor necrosis factor-alpha (TNF-α) in the cornea was assessed by quantitative (q) RT–PCR on days 10. The ocular irritation of LBP eye drops of corresponding concentrations was evaluated on 10- to 12-week-old female Sprague–Dawley rats.

Results

Compared with PBS-treated groups, mice treated with 0.625, 2.5, and 12.5 mg/ml LBP showed a significant improvement in the clinical signs of DED in a dose-dependent manner, including corneal epithelial integrity, corneal regularity, and tear production, as well as significant inhibition of inflammatory cell infiltration and TNF-α expression levels in the cornea. All corresponding concentrations of LBP eye drops revealed no obvious ocular irritation.

Conclusion

Topical application of LBP could ameliorate dry eye in a murine model of DED without obvious ocular irritation.

A review of meibomian gland structure, function, and contact lens wear

PURPOSE

To provide a balanced literature review of the studies that have evaluated the effect of contact lenses on meibomian gland (MG) health.

METHODS

A PubMed.gov literature search was conducted on or before May 15, 2021. No other time constraints were applied. Search terms included the following: "meibomian gland(s)" plus "contact lens(es)" or "meibography" plus "contact lens(es)". Only full text articles written in English were considered. The reference lists of recovered papers were used to identify articles missed during the primary search. Included articles were required to discuss the impact of contact lenses on MG morphology or function and were graded according to the level of evidence presented.

RESULTS

The literature indicates that contact lenses impact MG function; however, the data are equivocal regarding contact lenses inducing MG structural changes. The literature likewise indicates that the mechanism(s) by which contact lenses impact the MGs are likely multifactorial. Recent data suggests that MGs may have some plasticity. Detected differences between studies likely stem from varied populations evaluated, study designs, and the duration of the evaluation periods.

CONCLUSIONS

With this literature review finding conflicting relationships between MG health and contact lens use, future longitudinal studies with standardized clinical MG assessments are needed to determine the true impact of contact lenses on MG health. Until these data are obtained, contact lens wearers should undergo a full MG evaluation, especially because recent data suggest that MG treatments may restore MG structure and function.

Efficacy of Artificial Tears Based on an Extract of Artemia salina Containing Dinucleotides in a Rabbit Dry Eye Model

(1) Background: Artemia salina is a brine shrimp containing high concentrations of dinucleotides, molecules with properties for dry eye treatment. For this reason, the purpose of the study was to evaluate the effect of the artificial tears based on an extract of Artemia salina in a rabbit dry eye model. (2) Methods: A prospective and randomized study was carried out. Twenty rabbits were divided into 4 groups (n = 5, each group): healthy rabbits, dry eye rabbits, dry eye rabbits treated with hypromellose (HPMC), and dry eye rabbits treated with Artemia salina. Dry eye was induced by the topical instillation of 0.2% benzalkonium chloride. The measurements were performed before and after the treatment for 5 consecutive days. (3) Results: The topical instillation of artificial tears containing Artemia salina showed beneficial effects on tear secretion, tear break-up time, corneal staining, the density of Goblet cells, heigh of mucin cloud secreted by these cells, and mRNA levels of IL-1β and MMP9 in conjunctival cells. Compared with the HPMC, there was a statistically significant improvement (p < 0.05) with the Artemia salina in all the variables under study, except for the conjunctival hyperemia, density of Goblet cells, and mRNA levels of IL-6. (4) Conclusions: The potential of artificial tears based on Artemia salina as a secretagogue agent for dry eye treatment was confirmed, opening the door for future clinical trials and studies to extrapolate the findings for dry eye patients.

Stimuli-Responsive Nanoplatform-Assisted Photodynamic Therapy Against Bacterial Infections

Bacterial infections are common diseases causing tremendous deaths in clinical settings. It has been a big challenge to human beings because of the antibiotics abuse and the newly emerging microbes. Photodynamic therapy (PDT) is a reactive oxygen species-based therapeutic technique through light-activated photosensitizer (PS). Recent studies have highlighted the potential of PDT as an alternative method of antibacterial treatment for its broad applicability and high efficiency. However, there are some shortcomings due to the low selectivity and specificity of PS. Growing evidence has shown that drug delivery nanoplatforms have unique advantages in enhancing therapeutic efficacy of drugs. Particularly, stimuli-responsive nanoplatforms, as a promising delivery system, provide great opportunities for the effective delivery of PS. In the present mini-review, we briefly introduced the unique microenvironment in bacterial infection tissues and the application of PDT on bacterial infections. Then we review the stimuli-responsive nanoplatforms (including pH-, enzymes-, redox-, magnetic-, and electric-) used in PDT against bacterial infections. Lastly, some perspectives have also been proposed to further promote the future developments of antibacterial PDT.

Effects of intense pulsed light treatment on tear cytokines and clinical outcomes in meibomian gland dysfunction

Meibomian gland dysfunction (MGD) has become a prevalent ocular surface disorder. Its pathogenesis is regarded as a self-perpetuating inflammatory vicious circle. Intense Pulsed Light (IPL) treatment was recently applied to improve the meibomian gland function and reduce symptoms of MGD. However, studies investigating the change of specific inflammatory cytokines during IPL treatment remained sparse. To further figure out how IPL treatment modulates the inflammatory cytokines in tears of MGD, we therefore performed a cross-sectional study and enrolled 32 patients from March 2019 to December 2020. The patients received 3 sessions of IPL treatment (10 to 16 J/cm²) at 4-week interval. The signs and symptoms of MGD were evaluated by ocular surface disease index (OSDI), tear film breakup time (TBUT), and meibomian gland yield secretion score (MGYSS). The clinical evaluators and tear samples were analyzed at baseline and at each IPL treatment session. Concentrations of (chemokine ligand) CXCL1, (C-C motif chemokine) CCL11, (tumor necrosis factor) TNF-α, (interferon) IFN-γ, (interleukin) IL-2, IL-6 and (tissue inhibitor of metalloproteinase) TIMP-1were measured by Quantibody Human Dry Eye Disease Array1. OSDI significantly decreased after IPL treatment compared with baseline. TBUT and MGYSS increased consecutively during treatment. CXCL1, CCL11, TNF-α, IFN-γ, IL-2, IL-6 presented significantly decrease and TIMP-1 showed significantly increase from the pretreatment baseline. The changed concentrations of TNF-α, IFN-γ, IL-2, TIMP-1 correlated with TBUT, the changed values of CXCL1, TNF-α, IFN-γ, CCL11, IL-2, IL-6, TIMP-1 correlated with MGYSS, and the changed concentrations of CXCL1, IFN-γ, CCL11, IL-2, IL-6 correlated with TIMP-1. The data supported IPL treatment could significantly relieve both signs and symptoms of MGD. The therapeutic effect of IPL treatment may originate from regulation of inflammatory cytokines including CXCL1, TNF-α, IFN-γ, CCL11, IL-2, IL-6, and TIMP-1.

Pharmacological evaluation of innovative eye drop formulations containing TS-polysaccaride, hyaluronic acid and glycyrrhizin for irritative ocular diseases using in vitro reconstituted human corneal epithelium model

In vitro reconstructed human corneal tissue models are closer to in vivo human corneal tissue in term of morphology, biochemical and physiological properties, and represent a valid alternative to animal use for evaluating the pharmacological effects ophthalmic topically applied medical devices. In this experimental work the in vitro reconstructed human corneal tissues have been used for assessing the potential beneficial effects of an innovative ophthalmic formulation containing hyaluronic acid, glycyrrhizin and TS-polysaccharide for the treatment of symptomatic states on the eye surface including dry eye, itching, foreign body sensation and redness due allergic reaction. Corneal tissues have been treated with benzalkonium chloride for 24 h to induce cell damage and then treated with the tested items for 16 h. After the incubation period, tissue viability, TNF-α, IL-6 and MMP-9 have been assessed. Diclofenac has been used as reference anti-inflammatory drug. The novel formulation protected the tissues against benzalkonium chloride damage, while exerted a mild but not significant reduction of the anti-inflammatory mediator TNF-α.

CLEAR - Contact lens technologies of the future

Contact lenses in the future will likely have functions other than correction of refractive error. Lenses designed to control the development of myopia are already commercially available. Contact lenses as drug delivery devices and powered through advancements in nanotechnology will open up further opportunities for unique uses of contact lenses. This review examines the use, or potential use, of contact lenses aside from their role to correct refractive error. Contact lenses can be used to detect systemic and ocular surface diseases, treat and manage various ocular conditions and as devices that can correct presbyopia, control the development of myopia or be used for augmented vision. There is also discussion of new developments in contact lens packaging and storage cases. The use of contact lenses as devices to detect systemic disease has mostly focussed on detecting changes to glucose levels in tears for monitoring diabetic control. Glucose can be detected using changes in colour, fluorescence or generation of electric signals by embedded sensors such as boronic acid, concanavalin A or glucose oxidase. Contact lenses that have gained regulatory approval can measure changes in intraocular pressure to monitor glaucoma by measuring small changes in corneal shape. Challenges include integrating sensors into contact lenses and detecting the signals generated. Various techniques are used to optimise uptake and release of the drugs to the ocular surface to treat diseases such as dry eye, glaucoma, infection and allergy. Contact lenses that either mechanically or electronically change their shape are being investigated for the management of presbyopia. Contact lenses that slow the development of myopia are based upon incorporating concentric rings of plus power, peripheral optical zone(s) with add power or non-monotonic variations in power. Various forms of these lenses have shown a reduction in myopia in clinical trials and are available in various markets.

Evidence of Polyphenols Efficacy against Dry Eye Disease

Dry eye disease is a multifactorial pathology compromising the quality of life of patients, resulting in significant damage of the ocular surface and discomfort. The current therapeutical strategies are not able to definitively resolve the underlying causes and stop the symptoms. Polyphenols are promising natural molecules that are receiving increasing attention for their activity/effects in counteracting the main pathologic mechanisms of dry eye disease and reducing its symptoms. In the present review, a deep literature search focusing on the main polyphenols tested against dry eye disease was conducted, analyzing related in vitro, in vivo, and clinical studies to provide a comprehensive and current review on the state of the art. Polyphenols present multiple effects against dry eye diseases-related ocular surface injury. In particular, the observed beneficial effects of polyphenols on corneal cells are the reduction of the pathological processes of inflammation, oxidative stress, and apoptosis and modulation of the tear film. Due to numerous studies reporting that polyphenols are effective and safe for treating the pathological mechanisms of this ocular surface disease, we believe that future studies should confirm and extend the evidence of polyphenols efficacy in clinical practice against dry eye disease and help to develop new ophthalmic drug(s).

Circ-ITCH restrains the expression of MMP-2, MMP-9 and TNF-α in diabetic retinopathy by inhibiting miR-22

Diabetic retinopathy (DR), the most frequent complication of diabetes mellitus, is the principal cause of acquired blindness worldwide. Although the roles of circRNAs have been extensively explored, the detailed physiological and pathological functions of circRNAs in DR are less understood. Here, we studied the biological effects of circ-ITCH in diabetic retinal pigment epithelial cells (RPEs) and explored the underlying mechanisms. As our results shown, the RNA expression of circ-ITCH was significantly lower in RPEs isolated from diabetic rats than they were in those isolated from normal rats. While diabetes induced an increase in MMP-2, MMP-9 and TNF-α in RPEs, circ-ITCH overexpression exerted an inhibitory on these increases and knockdown of circ-ITCH reversed the inhibitory. In addition, increased expression of miR-22 in RPEs correlated with diabetes and downregulation of circ-ITCH. Remarkably, in the presence of miR-22 mimics, the effects of circ-ITCH on the MMP-2 and MMP-9 were both antagonized. Collectively, our data supports a cellular signaling cascade in which circ-ITCH-inhibited miR-22 activity modulates the expression of MMP-2, MMP-9 and TNF-α in DR.

Alpha-lipoic acid: A possible pharmacological agent for treating dry eye disease and retinopathy in diabetes

Alpha-lipoic acid (ALA) is a naturally occurring dithiol micronutrient which acts as a cofactor for mitochondrial enzyme activity. Due to its potential antioxidant activity, it is considered as "universal antioxidant". Previous studies reported the pharmacological benefits of ALA such as glycaemic control, improved insulin sensitivity and alleviation of diabetic complications such as neuropathy and cardiovascular diseases. Dry eye disease and retinopathy are prevalent in diabetic patients. Experimental studies demonstrated the beneficial effects of ALA in dry eye and diabetic retinopathy. ALA can prevent the dry eye by down regulating the expression of matrix metalloproteinase-9 in the corneal epithelial cells and activating the antioxidant status of the ocular surface. Furthermore, its direct antioxidant effect can also prevent oxidative stress-induced corneal surface erosion and lachrymal gland damage. ALA prevents diabetic retinopathy through inhibition of O-linked β-N-acetylglucosamine transferase and nuclear factor-kappa B activity and alleviation of oxidative stress. It can activate the nuclear factor erythroid-2-related factor 2 and AMP-activated protein kinase in retinal ganglion cells. Clinical trials conducted in pre-retinopathic diabetic patients showed ALA with genistein and vitamins could protect the retinal cells and decline the inflammatory effect in diabetic patients. However, studies are scant to explore its beneficial effects in dry eye disease and diabetic retinopathy. Therefore, this review article discusses an update on the role of ALA in dry eye disease and diabetic retinopathy, two ocular diseases prevalent in diabetic patients.

Ocular Surface Potential Difference Measured in Human Subjects to Study Ocular Surface Ion Transport

Purpose

The epithelium lining the ocular surface, which includes corneal and conjunctival epithelia, expresses the prosecretory chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) and the proabsorptive epithelial sodium channel (ENaC). Here, methodology was established to measure the millivolt (mV) potential differences at the ocular surface, called ocular surface potential difference (OSPD), in human subjects produced by ion transport.

Methods

OSPD was measured in human subjects in which a fluid-filled measuring electrode contacted a fluid pool created by eversion of the lateral lower eyelid, with a reference electrode placed subcutaneously in the forearm. Through the use of a high-impedance voltmeter, OSPD was measured continuously over 10 to 15 minutes in response to a series of perfusate fluid exchanges.

Results

Baseline OSPD (± SEM) in six normal human subjects was -21.3 ± 3.6 mV. OSPD depolarized by 1.7 ± 0.6 mV following the addition of the ENaC inhibitor amiloride, hyperpolarized by 6.8 ± 1.5 mV with a zero chloride solution, and further hyperpolarized by 15.9 ± 1.6 mV following CFTR activation by isoproterenol. The isoproterenol-induced hyperpolarization was absent in two cystic fibrosis subjects lacking functional CFTR. OSPD measurement produced minimal epithelial injury.

Conclusions

Our results establish the feasibility and safety of OSPD measurement in humans and demonstrate robust CFTR activity, albeit minimal ENaC activity, at the ocular surface. OSPD measurement may be broadly applicable to investigate fluid transport mechanisms and test drug candidates to treat ocular surface disorders.

Translational Relevance

To the best of our knowledge, this is the first measurement of the electrical potential generated by the ocular surface epithelium in human subjects, offering a new approach to study ocular surface function and health.

Case Series of Perforated Keratomycosis after Laser-Assisted In Situ Keratomileusis

Background

Fungal keratitis is an extremely rare complication of laser vision correction resulting in poor visual outcomes. Amniotic membrane transplantation should be kept in mind in eyes with corneal perforation prior to penetrating keratoplasty.

Aim

To assess the outcomes of multilayered fresh amniotic membrane transplantation (MLF-AMT) in patients with severe keratomycosis after laser-assisted in situ keratomileusis (LASIK). Study design. Hospital-based prospective interventional case series.

Methods

Five eyes of 5 patients were included in the study. All cases underwent microbiological scrapings from residual bed and intrastromal injections of amphotericin (50 mcg/mL), with flap amputation if needed, followed by topical 5% natamycin and 0.15% amphotericin. MLF-AMT was performed after corneal perforation. Later, penetrating keratoplasty (PK) was performed when corneal opacity compromised visual acuity. The outcome measures were complete resolution of infection, corneal graft survival, and best-corrected visual acuity (BCVA).

Results

The mean age of patients was 22 ± 1.2 years with 4/5 (80%) were females. The mean interval between LASIK and symptom onset was 8.8 ± 1 day, and the mean interval between symptom onset and referral was 14 ± 1.4 days. Potassium hydroxide (KOH) smears showed filamentous fungi, and Sabouraud's medium grew Aspergillus in all cases. Melted flaps were amputated in 4 (80%) cases. MLF-AMT was performed in all cases due to corneal perforation after a mean time of 12.4 ± 1.2 days of antifungals. In all cases, complete resolution of infection was seen 26 ± 1.8 days after MLF-AMT, and optical PK was done at a mean of 2.4 months later. No postoperative complications after MLF-AMT or PK were observed, with a 0% incidence of corneal graft rejection, and a final BCVA ranged from 20/20 to 20/80 after a mean follow-up of 14 ± 1.1 months.

Conclusion

MLF-AMT is a safe and valid option to manage corneal perforation during keratmycosis treatment to avoid emergency therapeutic keratoplasty.

Case Series of Brittle Cornea Syndrome

Purpose

This case series demonstrate diagnostic features, treatment options, and challenges for Brittle Cornea Syndrome. Observations. Three cases presented with bluish sclera and extremely thin cornea. Genetic workup was performed and confirmed the diagnosis of Brittle Cornea Syndrome, a rare autosomal recessive disorder characterized by corneal thinning and blue sclera. Case 1 was a 4-year-old boy who developed cataract and glaucoma after undergoing right tectonic penetrating keratoplasty (PK) secondary to a spontaneous corneal rupture. Glaucoma was controlled medically. Later, the kid underwent right transcorneal lensectomy and vitrectomy with synechiolysis. After 6 weeks, he sustained graft dehiscence that was repaired using onlay patch graft. Case 2 was a 7-year-old boy who underwent PK in the right eye, then a pericardial patch graft in the left eye following spontaneous corneal rupture. Glaucoma in both eyes was controlled medically. Case 3 was the 2-year-old sister of the 2^nd case. She had a pachymetry of 238 μm OD and 254 μm OD and 254 

Conclusions

Long-term follow-up of children diagnosed with Brittle Cornea Syndrome is paramount to minimize the morbidity of corneal rupture and late-onset extraocular conditions.