Expression of Matrix Metalloproteinases 2 and 9 in Experimental Corneal Injury and Fungal Keratitis

Matrix Metalloproteinases and the Pathogenesis of Recurrent Corneal Erosions and Epithelial Basement Membrane Dystrophy

Matrix metalloproteinases (MMPs) are a group of proteolytic enzymes which are members of the zinc endopeptidase family. They have the ability to degrade extracellular matrix elements, allowing for the release of binding molecules and cell migration. Although metalloproteinases regulate numerous physiological processes within the cornea, overexpression of metalloproteinase genes and an imbalance between the levels of metalloproteinases and their inhibitors can contribute to the inhibition of repair processes, the development of inflammation and excessive cellular proliferation. The involvement of MMPs in the pathogenesis of dystrophic corneal diseases needs clarification. Our analyses focus on the involvement of individual metalloproteinases in the pathogenesis of recurrent corneal erosions and highlight their impact on the development of corneal epithelial basement membrane dystrophy (EBMD). We hypothesize that abnormalities observed in patients with EBMD may result from the accumulation and activation of metalloproteinases in the basal layers of the corneal epithelium, leading to basement membrane degradation. A barrier formed from degradation materials inhibits the normal migration of epithelial cells to the superficial layers, which contributes to the development of the aforementioned lesions. This hypothesis seems to be lent support by the elevated concentrations of metalloproteinases in the corneal epithelium of these patients found in our previous studies on the relationships between MMPs and recurrent corneal erosions.

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.

The role of neutrophils in corneal nerve regeneration

BACKGROUND

To investigate the role of neutrophils in corneal nerve regeneration.

METHODS

A mouse model simulating corneal nerve injury was established and samples from corneal scraping with and without neutrophil closure were collected. These samples were used for corneal nerve staining, ribonucleic acid sequencing, and bioinformatics. Differential expression analysis was used to perform enrichment analysis to identify any significant differences between these two groups. The differential genes were then intersected with neutrophil-associated genes and a protein-protein interaction network was constructed using the intersected genes. The immune infiltration between the two groups was examined along with the immune cell variation between the high and low gene expression groups.

RESULTS

Neutrophil removal delays corneal epithelial and nerve regeneration. A total of 546 differential genes and 980 neutrophil-associated genes, with 27 genes common to both sets were obtained. Molecular Complex Detection analysis yielded five key genes, namely integrin subunit beta 2 (ITGB2), matrix metallopeptidase 9 (MMP9), epidermal growth factor (EGF), serpin family E member 1 (SERPINE1), and plasminogen activator urokinase receptor (PLAUR). Among these genes, ITGB2, SERPINE1, and PLAUR exhibited increased expression in the neutrophil-confined group, while MMP9 and EGF showed decreased expression, with MMP9 and EGF displaying a more significant difference. Immune infiltration was also observed between the two groups, revealing significant differences in the infiltration of M0 macrophages, activated mast cells, and neutrophils. Moreover, the neutrophil levels were lower in the groups with low MMP9 and EGF expressions and higher in the high-expression group.

CONCLUSION

Neutrophil confinement might significantly affect the MMP9 and EGF expression levels. Strategies to inhibit MMP9 could potentially yield therapeutic benefits.

Fungal Keratitis and Corneal Perforation as a Rare Complication of Corneal Collagen Cross-Linking Treatment

PURPOSE

The aim of this study was to report a case of fungal keratitis with subsequent corneal perforation after corneal collagen cross-linking (CXL) treatment performed for keratoconus.

CASE REPORT

A 20-year-old woman presented with redness and discharge in the left eye. She had a history of bilateral CXL procedure performed for keratoconus elsewhere 4 days earlier. The visual acuity was hand motion in the left eye. Slit-lamp examination revealed extended corneal melting with surrounding infiltrates. The patient was hospitalized, and corneal epithelial scraping samples were sent for microbiological assessment. In the meantime, empirical antibiotic therapy (fortified topical antibiotics: vancomycin 50 mg/mL, ceftazidime 50 mg/mL, and fluconazole 2 mg/mL q1 hour) was initiated. In direct microscopy of the corneal scraping, septate hyaline fungal hyphae were detected and topical fluconazole was switched to topical voriconazole (10 mg/mL). Three days after hospitalization, corneal melting progressed to perforation and corneal suturing with 10-0 monofilament was performed to reform the anterior chamber. Complete resolution of keratitis with residual scarring was noticed in 2 weeks. Three months later, penetrating keratoplasty was performed to obtain better visual acuity.

CONCLUSIONS

CXL with riboflavin has become a common procedure to prevent keratoconus progression by strengthening the biomechanical specialties of the cornea. Although the treatment itself has been used in the management of microbial keratitis and related corneal melting, fungal keratitis and corneal perforation after a CXL procedure for keratoconus might also be detected. Clinicians should be aware of this rare but devastating complication of CXL treatment and start prompt treatment when suspected.

Identification of hub genes and pathways of ferroptosis in Fusarium keratitis by bioinformatics methods

Background

Fungal keratitis is a common blinding eye disease, and Fusarium is one of the main species that cause fungal keratitis. As is well known, oxidative stress plays an important role in Fusarium keratitis and it is also a significant initiating factor of ferroptosis. But the relationship between Fusarium keratitis and ferroptosis is currently unclear. This study aimed to speculate and validate potential ferroptosis-related genes in Fusarium keratitis using bioinformatics analysis, which provided ideas for further research on its specific mechanism and new targets for its treatment.

Methods

The microarray expression profiling dataset (GSE58291) came from Gene Expression Omnibus (GEO). The differentially expressed genes (DEGs) were obtained by the limma package of the R software. The DEGs were performed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Then, the DEGs were intersected with the genes in the ferroptosis database. The top 5 hub genes were obtained by the protein-protein interaction (PPI) network analysis and the cytoHubba plug-in of Cytoscape software. The hub genes were subjected to GSEA analysis. Then we analyzed the immune infiltration of the samples by CIBERSORT and ssGSEA algorithm. Finally, we validated the mRNA of hub genes by qPCR.

Results

A total of 1,368 DEGs were identified and 26 ferroptosis-related DEGs were obtained. At the same time, ferroptosis-related pathways were enriched by GO and KEGG using DEGs. HMOX1, CYBB, GPX2, ALOX5 and SRC were obtained by the PPI network analysis and the cytoHubba plug-in of Cytoscape software. The iron metabolism and immune response related pathways were enriched using GSEA. They included hematopoietic cell lineage, lysosome and FC gamma R mediated phagocytosis. T cells follicular helper, monocytes, macrophages and mast cells might play an important role in Fusarium keratitis using analysis of immune infiltration. Finally, qPCR confirmed that the expression of HMOX1, CYBB, ALOX5 mRNA in the DON group was significantly elevated, while the expression of GPX2 were significantly decreased.

Conclusions

Ferroptosis may play an important role in Fusarium keratitis. HMOX1, CYBB, ALOX5 and GPX2 may be key ferroptosis-related genes in the pathogenesis of Fusarium keratitis.

Fusarium Keratitis-Review of Current Treatment Possibilities

In many parts of the world, fungi are the predominant cause of infectious keratitis; among which, Fusarium is the most commonly isolated pathogen. The clinical management of this ophthalmic emergency is challenging. Due to the retardation of the first symptoms from an injury and the inability to differentiate fungal from bacterial infections based on clinical symptoms and difficult microbial diagnostics, proper treatment, in many cases, is postponed. Moreover, therapeutical options of Fusarium keratitis remain limited. This paper summarizes the available treatment modalities of Fusarium keratitis, including antifungals and their routes of administration, antiseptics, and surgical interventions.

Role of Matrix Metalloproteinase 9 in Ocular Surface Disorders

OBJECTIVES

(1) To explore the role and significance of Matrix Metalloproteinase 9 (MMP-9), a proteolytic enzyme, in various ocular surface diseases of inflammatory, infectious, and traumatic etiology (2), to further elucidate the molecular mechanisms responsible for its overexpression in ocular surface disease states, and (3) to discuss possible targets of therapeutic intervention.

METHODS

A literature review was conducted of primary sources from 1995 onward using search results populated from the US National Library of Medicine search database.

RESULTS

MMP-9 overexpression has been found in in vitro and in vivo models of dry eye disease (DED), corneal ulceration, microbial keratitis, corneal neovascularization, ultraviolet light-induced radiation, and a host of additional surface pathologies. MMP-9 is involved in an intricate signal transduction cascade that includes induction by many proinflammatory molecules including interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-a), nuclear factor kappa light chain enhancer of activated B cells (NF-kB), platelet-activating factor, activator protein 1 (AP-1), and transforming growth factor beta (TGF-B). MMP-9 expression is blunted by a diverse array of molecular factors, such as tissue inhibitors of metalloproteinases, cyclosporine A (CyA), PES_103, epigalloccatechin-3-gallate (EGCG), N-acetylcysteine (NaC), ascorbate, tetracyclines, and corticosteroids. Inhibition of MMP-9 frequently led to improvement of ocular surface disease.

CONCLUSIONS

Novel insights into the mechanistic action of MMP-9 provide potential for new therapeutic modulations of ocular surface diseases mediated by its overexpression.

Tissue Inhibitor of Metalloproteinase (TIMP) Peptidomimetic as an Adjunctive Therapy for Infectious Keratitis

Matrix metalloproteinase 9 (MMP-9) has a key role in many biological processes, and while it is crucial for a normal immune response, excessive release of this enzyme can lead to severe tissue damage, as evidenced by proteolytic digestion and perforation of the cornea during infectious keratitis. Current medical management strategies for keratitis mostly focus on antibacterial effects, but largely neglect the role of excess MMP activity. Here, a cyclic tissue inhibitor of metalloproteinase (TIMP) peptidomimetic, which downregulated MMP-9 expression both at the mRNA and protein levels as well as MMP-9 activity in THP-1-derived macrophages, is reported. A similar downregulating effect could also be observed on α smooth muscle actin (α-SMA) expression in fibroblasts. Furthermore, the TIMP peptidomimetic reduced Pseudomonas aeruginosa-induced MMP-9 activity in an ex vivo porcine infectious keratitis model and histological examinations demonstrated that a decrease of corneal thickness, associated with keratitis progression, was inhibited upon peptidomimetic treatment. The presented approach to reduce MMP-9 activity thus holds great potential to decrease corneal tissue damage and improve the clinical success of current treatment strategies for infectious keratitis.

Experimental Models for Fungal Keratitis: An Overview of Principles and Protocols

Fungal keratitis is a potentially blinding infection of the cornea that afflicts diverse patient populations worldwide. The development of better treatment options requires a more thorough understanding of both microbial and host determinants of pathology, and a spectrum of experimental models have been developed toward this end. In vivo (animal) models most accurately capture complex pathological outcomes, but protocols may be challenging to implement and vary widely across research groups. In vitro models allow for the molecular dissection of specific host cell–fungal interactions, but they do so without the appropriate environmental/structural context; ex vivo (corneal explant) models provide the benefits of intact corneal tissue, but they do not provide certain pathological features, such as inflammation. In this review, we endeavor to outline the key features of these experimental models as well as describe key technical variations that could impact study design and outcomes.

Three kinds of corneal host cells contribute differently to corneal neovascularization

Background

Corneal neovascularization (angiogenesis and lymphangiogenesis) compromises corneal transparency and transplant survival, however, the molecular mechanisms of corneal host epithelial and stromal cells in neovascularization have not yet been fully elucidated. Furthermore, the contribution and mechanism of corneal host endothelial cells involved in neovascularization are largely unexplored.

Methods

Liquid chromatography-mass spectrometry, immunoblotting, and ELISA were used to screen and identify potential neovascularization-related factors in human full-thickness vascularized corneal tissues. Lipopolysaccharide was used to induce inflammation in three kinds of corneal host cells in vitro, including corneal epithelial, stromal, and endothelial cells. Fungus was used to establish an animal model of corneal neovascularization in vivo. Tube formation and spheroid sprouting assays were used to evaluate the contribution of three kinds of corneal host cells to the degree of neovascularization under various stimuli. Matrix metalloproteinase (MMP)-2, alpha-crystallin A chain (CRYAA), galectin-8, Bcl-2, neuropilin-2, MMP-9 plasmids, and recombinant human fibronectin were used to identify the key proteins of corneal host cells involved in corneal inflammatory neovascularization.

Findings

All three kinds of corneal host cells influenced corneal neovascularization to varying degrees. MMP-9 in human corneal epithelial cells, MMP-2, and CRYAA in human corneal stromal cells, and MMP-2 and galectin-8 in human corneal endothelial cells are potential key proteins that participate in corneal inflammatory neovascularization.

Interpretation

Our data indicated that both the effects of key proteins and corneal host cells involved should be considered for the treatment of corneal inflammatory neovascularization.

Exocellular extract of Fusarium oxysporum, fungus free, is able to permeate and act selectively in skin

The skin is an important gateway for Fusarium infection in humans. Our hypothesis is that metabolites produced by Fusarium oxysporum should change the barrier structure to permeate the skin. Male Wistar rats received a topical application of a solution (0.05 mg/mL) of Fusarium metabolites. The animals were euthanized 3, 6, 12, 24 h after and the skin was processed for immunostaining by laminin and E-cadherin to investigate whether the Fusarium metabolites can break the barrier of healthy skin. Other techniques were employed: H&E to study the morphology; metalloproteinase-9 (MMP-9), TUNEL, and PCNA immunostaining to evaluate the inflammation, cell death, and proliferation, respectively. There was an inflammatory response mainly centered in the dermis. Qualitatively, the skin of the experimental group showed reduced E-cadherin and laminin immunostaining at 3, 12, and 24 h. Higher intensity staining by TUNEL at 3 h, and PCNA at 6, 12, and 24 h. There was intense MMP-9 activity at 6, 12, and 24 h. None of analyses revealed any changes in the epidermis. It was concluded that the fraction was able to permeate the skin and act selectively in dermis, inducing inflammatory response, increasing MMP-9 immunostaining, inducing apoptosis, and reducing E-cadherin and laminin immunostaining.

Corneal Cross-Linking Has No Effect on Matrix Metalloproteinase 9 and 13 Levels During Fungal Keratitis on the Early Stage

The aim of our study was to investigate matrix metalloproteinases, MMP-9 and MMP-13 levels, in the rabbit model of Fusarium and Candida keratitis treated by corneal cross-linking (PACK-CXL). Rabbit corneas were inoculated with fungal inoculum for keratitis. Each group divided into four subgroups, including un-treated group, PACK-CXL group, voriconazole group and PACK-CXL plus voriconazole group. PACK-CXL was applied with 0.25% riboflavin in accelerated Dresden protocol, and 0.1% voriconazole drops were administered. All corneal buttons excised at tenth day after ophthalmological examination. Fungal cell counts and Scheiber scores were determined in all groups. Corneal tissue MMP mRNA levels were evaluated quantitative reverse transcriptase PCR. The difference in MMP-9 and MMP-13 levels at all groups was not statistically significant (p > 0.05). PACK-CXL with 0.25% riboflavin either alone or combined with antifungal drops was unable to provide decline in inflammatory findings in both macroscopic and microscopic levels similar to medical antifungal treatment.

The Effect of High Intensity Focused Ultrasound Keratoplasty on Rabbit Anterior Segment

Purpose. To evaluate the safety of high-intensity focused ultrasound keratoplasty as a treatment for presbyopia by examining its effect on the rabbit anterior segment. Methods. The right corneas of 36 New Zealand rabbits were treated with HIFU keratoplasty. The animals were sacrificed at 1, 7, 15, 30, 60, and 90 days after operation. Collagen type I, MMP-2, and MMP-9 were evaluated using immunohistochemistry. For the detection of apoptosis, the TUNEL method was applied. The SOD and MDA levels were analyzed with assay kits. Results. Collagen type I, MMP-2, and MMP-9 levels were altered after the operation but returned to normal within 90 days. The apoptotic index (AI) of the corneal cells decreased from 1 to 30 days gradually. No apoptosis was observed in the epithelial cells of the lens, and the SOD and MDA levels were normal at any time point. Conclusion. After HIFU keratoplasty, the histomorphology of the cornea changed, the corneal collagen type I levels decreased, the corneal MMP-2 and MMP-9 levels increased, and the corneal cells underwent apoptosis for a period of time. Ninety days after the operation, the levels returned to normal, and the lenses were not affected. Thus, HIFU presents good biological safety for eyes.

Time-dependent matrix metalloproteinases and tissue inhibitor of metalloproteinases expression change in fusarium solani keratitis

AIM

To investigate matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) expression during the progress of fusarium solani (F.solani) keratitis in a rat model.

METHODS

A rat model of F.solani keratitis was produced using corneal scarification and a hand-made contact lens. MMPs and TIMPs expressiond were explored in this rat model of F.solani keratitis using real-time polymerase chain reaction (PCR) and DIF. GM6001 (400 µmol/mL) was used to treat infected corneas. The keratitis duration, amount and area of corneal neovascularization (CNV) were evaluated.

RESULTS

MMP-3 expression was 66.3 times higher in infected corneas compared to normal corneas. MMP-8, -9, and -13 expressions were significantly upregulated in the mid-period of the infection, with infected-to-normal ratios of 4.03, 39.86, and 5.94, respectively. MMP-2 and -7 expressions increased in the late period, with the infected-to-normal ratios of 5.94 and 16.22, respectively. TIMP-1 expression was upregulated in the early period, and it was 43.17 times higher in infected compared to normal corneas, but TIMP-2, -3, and -4 expressions were mildly downregulated or unchanged. The results of DIF were consistent with the result of real-time PCR. GM6001, a MMPs inhibitor, decreased the duration of F.solani infection and the amount and area of CNV.

CONCLUSION

MMPs and TIMPs contributed into the progress of F.solani keratitis.

MMP-8 Is Critical for Dexamethasone Therapy in Alkali-Burned Corneas Under Dry Eye Conditions

Our previous studies have shown that Dexamethasone (Dex) reduced the expression of matrix-metalloproteinases (MMPs -1,-3,-9,-13), IL-1β and IL-6, while it significantly increased MMP-8 mRNA transcripts in a concomitant dry eye and corneal alkali burn murine model (CM). To investigate if MMP-8 induction is responsible for some of the protective effects of Dex in CM, MMP-8 knock out mice (MMP-8KO) were subjected to the CM for 2 or 5 days and topically treated either with 2 μl of 0.1% Dexamethasone (Dex), or saline QID. A separate group of C57BL/6 mice were topically treated with Dex or BSS and received either 100 nM CAM12 (MMP-8 inhibitor) or vehicle IP, QD. Here we demonstrate that topical Dex treated MMP-8KO mice subjected to CM showed reduced corneal clarity, increased expression of inflammatory mediators (IL-6, CXCL1, and MMP-1 mRNA) and increased neutrophil infiltration at 2D and 5D compared to Dex treated WT mice. C57BL/6 mice topically treated with Dex and CAM12 IP recapitulated findings seen with MMP-8KO mice. These results suggest that some of the anti-inflammatory effects of Dex are mediated through increased MMP-8 expression. J. Cell. Physiol. 231: 2506-2516, 2016. © 2016 Wiley Periodicals, Inc.

Potential role of nuclear receptor ligand all-trans retinoic acids in the treatment of fungal keratitis

Fungal keratitis (FK) is a worldwide visual impairment disease. This infectious fungus initiates the primary innate immune response and, later the adaptive immune response. The inflammatory process is related to a variety of immune cells, including macrophages, helper T cells, neutrophils, dendritic cells, and Treg cells, and is associated with proinflammatory, chemotactic and regulatory cytokines. All-trans retinoic acids (ATRA) have diverse immunomodulatory actions in a number of inflammatory and autoimmune conditions. These retinoids regulate the transcriptional levels of target genes through the activation of nuclear receptors. Retinoic acid receptor α (RAR α), retinoic acid receptor γ (RAR γ), and retinoid X receptor α (RXR α) are expressed in the cornea and immune cells. This paper summarizes new findings regarding ATRA in immune and inflammatory diseases and analyzes the perspective application of ATRA in FK.

Immunohistochemical expression of matrix metalloproteinases in the rabbit corneal epithelium upon UVA and UVB irradiation

Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in tissue remodeling and wound healing. These enzymes degrade and also synthesize components of the extracellular matrix. Overexpression of MMPs results in excessive extracellular matrix degradation and tissue destruction. In the cornea, destructive processes may lead to scarring and loss of vision. In this study MMPs (types 1, 2, 7, 8, 9 and 14) were examined immunohistochemically in the normal rabbit corneal epithelium and in epithelium irradiated in vivo with similar doses of UVB or UVA radiation (UVB rays 312 nm, UVA rays 365 nm, daily dose 1.01 J/cm(2) for four days). Results show that MMPs studied revealed low expression in the normal corneal epithelium, whereas after repeated UVB irradiation the expression of MMPs was significantly increased in the corneal epithelium, in ascending order: MMP-2, MMP-9, MMP-1, and MMP-7 with MMP-8. In contrast, compared to normal corneas, repeated UVA radiation did not significantly change the expression of MMPs in the irradiated corneal epithelium. MMP-14 was expressed at very low levels in all studied corneas, whereas no significant changes were detected upon UV exposure. In conclusion, UV radiation of shorter wavelength (UVB) induced an increase in expression of all MMPs except MMP-14. It is suggested that overexpression of MMPs in the corneal epithelium contributes to the damaging effect of UVB radiation to the cornea.

Novel mucoadhesive polysaccharide isolated from Bletilla striata improves the intraocular penetration and efficacy of levofloxacin in the topical treatment of experimental bacterial keratitis

OBJECTIVES

The objective of the present study was to evaluate a novel mucoadhesive polymer extracted from Bletilla striata for ocular delivery of 0.5% levofloxacin in rabbits, and to determine its improved efficacy against experimental keratitis.

METHODS

B. striata polysaccharide (BsP) was subjected to cell cytotoxicity and ferning tests. The pharmacokinetics and bioavailability of topically applied 0.5% levofloxacin-BsP eye drops was investigated and compared with 0.5% levofloxacin eye drops (Cravit). Experimental Staphylococcus aureus keratitis was induced and treated with levofloxacin or levofloxacin-BsP eye drops.

KEY FINDINGS

BsP markedly increased the proliferative capacity of a human corneal epithelial [corrected] cell line. The ferning test showed that BsP exhibited optimal performance as a tear fluid. The polysaccharides significantly increased intra-aqueous penetration and corneal accumulation in rabbits. Treatment with levofloxacin-BsP reduced the number of organisms more significantly than eye drops containing levofloxacin alone.

CONCLUSIONS

BsP appears to be a promising candidate as a vehicle for topical ophthalmic drug delivery, especially for antibiotics.

Ocular fungal infections

PURPOSE

Microbiology, clinical perspective of ocular fungal infections, and the experimental models were overviewed.

METHODS

Review of published studies were evaluated and personal experience was mentioned. In this review, clinical features of keratitis and endogenous and exogenous endophthalmitis are also mentioned, but this article mainly focused on laboratory diagnosis and the experimental models of ophthalmic mycoses.

RESULTS

Fungal infections were discussed according to the anatomical part of the eye involved in the disease. Trauma is the most important predisposing cause; the species of Fusarium, Aspergillus, and Candida are the most frequently isolated organisms. Laboratory methods, such as culture, remains the cornerstone of diagnosis; direct microscopic detection of fungal structures in ocular samples permits a rapid presumptive diagnosis. New approaches, such as serological and molecular methods, have been widely used in recent years. A variety of antifungals have been evaluated in the therapy of this condition. Experimental models would facilitate investigations exploring the pathophysiology, cell biology, genetics, immunology, and therapy of this disease.

CONCLUSIONS

Fungal infections of the eye continue to be an important cause of ocular morbidity, particularly in the developing world. Understanding ocular infections will improve the outcome of this condition.

Expression of matrix metalloproteinases during experimental Candida albicans keratitis

PURPOSE

This study was designed to investigate the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) during the inception and progression of experimental keratomycosis.

METHODS

Scarified corneas of adult BALB/c mice were topically inoculated with Candida albicans strain SC5314 and monitored for disease severity. Infected and mock-infected corneas were compared at 1 day post inoculation (p.i.) with a murine gene microarray. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) determined MMP and TIMP levels at 1, 3, and 7 days p.i. for infected, mock-infected, and normal corneas. Immunostaining localized target proteins at 1 day p.i.

RESULTS

Eyes inoculated with C. albicans developed corneal infection with a mean clinical score of 8.2+/-0.8 at 1 day p.i. Compared to controls at 1 day p.i., MMP-8, -9, -10, -12, -13, -19, and TIMP-1 were significantly upregulated from fivefold to 375-fold by microarray and from threefold to 78-fold by real-time RT-PCR. Upregulated MMPs and TIMP-1 in the corneal epithelium and stroma of infected eyes correlated with the influx of acute inflammatory cells. Neither MMP-8 nor -13 expression was affected by mechanical trauma, but both increased >100-fold during the week after the onset of fungal keratitis. TIMP-1 expression rose from 21-fold more than controls at 1 day to 46-fold at 7 days p.i. by RT-PCR.

CONCLUSIONS

Transcriptional and translational levels of MMP-8, -9, -13, and TIMP-1 increase during the early stages of C. albicans keratitis, confirming findings for MMP-9 and TIMP-1 in other infectious keratitis models and suggesting roles for MMP-8 and -13.

First aid for complications of infectious keratitis

Infectious keratitis is a fairly common entity in India. However while paying attention to the primary entity, the associated events may be overlooked. Enhanced pain usually suggests a worsening of the condition or development of associated problems like secondary glaucoma. However, contrary to logic, a sudden decrease in pain is also likely to suggest a worsening, e.g. perforation of the corneal ulcer. Various such problems with their management are outlined.