Expression of matrix metalloproteinase 2 and 9 in experimentally wounded canine corneas and spontaneous chronic corneal epithelial defects

Squishy matters - Corneal mechanobiology in health and disease

The cornea, as a dynamic and responsive tissue, constantly interacts with mechanical forces in order to maintain its structural integrity, barrier function, transparency and refractive power. Cells within the cornea sense and respond to various mechanical forces that fundamentally regulate their morphology and fate in development, homeostasis and pathophysiology. Corneal cells also dynamically regulate their extracellular matrix (ECM) with ensuing cell-ECM crosstalk as the matrix serves as a dynamic signaling reservoir providing biophysical and biochemical cues to corneal cells. Here we provide an overview of mechanotransduction signaling pathways then delve into the recent advances in corneal mechanobiology, focusing on the interplay between mechanical forces and responses of the corneal epithelial, stromal, and endothelial cells. We also identify species-specific differences in corneal biomechanics and mechanotransduction to facilitate identification of optimal animal models to study corneal wound healing, disease, and novel therapeutic interventions. Finally, we identify key knowledge gaps and therapeutic opportunities in corneal mechanobiology that are pressing for the research community to address especially pertinent within the domains of limbal stem cell deficiency, keratoconus and Fuchs' endothelial corneal dystrophy. By furthering our understanding corneal mechanobiology, we can contextualize discoveries regarding corneal diseases as well as innovative treatments for them.

Ferrostatin-1-loaded liposome for treatment of corneal alkali burn via targeting ferroptosis

Alkali burn is a potentially blinding corneal injury. During the progression of alkali burn-induced injury, overwhelmed oxidative stress in the cornea triggers cell damage, including oxidative changes in cellular macromolecules and lipid peroxidation in membranes, leading to impaired corneal transparency, decreased vision, or even blindness. In this study, we identified that ferroptosis, a type of lipid peroxidation-dependent cell death, mediated alkali burn-induced corneal injury. Ferroptosis-targeting therapy protected the cornea from cell damage and neovascularization. However, the specific ferroptosis inhibitor ferrostatin-1 (Fer-1) is hydrophobic and cannot be directly applied in the clinic. Therefore, we developed Fer-1-loaded liposomes (Fer-1-NPs) to improve the bioavailability of Fer-1. Our study demonstrated that Fer-1-NPs exerted remarkable curative effects regarding corneal opacity and neovascularization in vivo. The efficacy was comparable to that of dexamethasone, but without appreciable side effects. The significant suppression of ferroptosis (induced by lipid peroxidation and mitochondria disruption), inflammation, and neovascularization might be the mechanisms underlying the therapeutic effect of Fer-1-NPs. Moreover, the Fer-1-NPs treatment showed no signs of cytotoxicity, hematologic toxicity, or visceral organ damage, which further confirmed the biocompatibility. Overall, Fer-1-NPs provide a new prospect for safe and effective therapy for corneal alkali burn.

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.

Topical Application of Hyaluronic Acid-RGD Peptide-Coated Gelatin/Epigallocatechin-3 Gallate (EGCG) Nanoparticles Inhibits Corneal Neovascularization Via Inhibition of VEGF Production

Neovascularization (NV) of the cornea disrupts vision which leads to blindness. Investigation of antiangiogenic, slow-release and biocompatible approaches for treating corneal NV is of great importance. We designed an eye drop formulation containing gelatin/epigallocatechin-3-gallate (EGCG) nanoparticles (NPs) for targeted therapy in corneal NV. Gelatin-EGCG self-assembled NPs with hyaluronic acid (HA) coating on its surface (named GEH) and hyaluronic acid conjugated with arginine-glycine-aspartic acid (RGD) (GEH-RGD) were synthesized. Human umbilical vein endothelial cells (HUVECs) were used to evaluate the antiangiogenic effect of GEH-RGD NPs in vitro. Moreover, a mouse model of chemical corneal cauterization was employed to evaluate the antiangiogenic effects of GEH-RGD NPs in vivo. GEH-RGD NP treatment significantly reduced endothelial cell tube formation and inhibited metalloproteinase (MMP)-2 and MMP-9 activity in HUVECs in vitro. Topical application of GEH-RGD NPs (once daily for a week) significantly attenuated the formation of pathological vessels in the mouse cornea after chemical cauterization. Reduction in both vascular endothelial growth factor (VEGF) and MMP-9 protein in the GEH-RGD NP-treated cauterized corneas was observed. These results confirm the molecular mechanism of the antiangiogenic effect of GEH-RGD NPs in suppressing pathological corneal NV.

Risk factors influencing survival of acellular porcine corneal stroma in infectious keratitis: a prospective clinical study

Background

A worldwide lack of donor corneas demands the bioengineered corneas be developed as an alternative. The primary objective of the current study was to evaluate the efficacy of acellular porcine corneal stroma (APCS) transplantation in various types of infectious keratitis and identify risk factors that may increase APCS graft failure.

Methods

In this prospective interventional study, 39 patients with progressive infectious keratitis underwent therapeutic lamellar keratoplasty using APCS and were followed up for 12 months. Data collected for analysis included preoperative characteristics, visual acuity, graft survival and complications. Graft survival was evaluated by the Kaplan–Meier method and compared with the log-rank test.

Results

The percentage of eyes that had a visual acuity of 20/40 or better increased from 10.3% preoperatively to 51.2% at 12 months postoperatively. Twelve patients (30.8%) experienced graft failure within the follow-up period. The primary reasons given for graft failure was noninfectious graft melting (n = 5), and the other causes included recurrence of primary infection (n = 4) and extensive graft neovascularization (n = 3). No graft rejection was observed during the follow-up period. A higher relative risk (RR) of graft failure was associated with herpetic keratitis (RR = 8.0, P = 0.046) and graft size larger than 8 mm (RR = 6.5, P < 0.001).

Conclusions

APCS transplantation is an alternative treatment option for eyes with medically unresponsive infectious keratitis. Despite the efficacy of therapeutic lamellar keratoplasty with APCS, to achieve a good prognosis, restriction of surgical indications, careful selection of patients and postoperative management must be emphasized.

Trial registration Prospective Study of Deep Anterior Lamellar Keratoplasty Using Acellular Porcine Cornea, NCT03105466. Registered 31 August 2016, ClinicalTrails.gov

Case Reports for Topical Treatment of Corneal Ulcers with a New Matrix Therapy Agent or RGTA® in Dogs

Superficial corneal ulcers that fail to heal within a normal time period and are refractory to conventional therapy in dogs are common in veterinary practice. Different etiologies can lead to this result, including spontaneous chronic corneal epithelial defects (SCCEDs) and ulcerative keratitis associated with bullous keratopathy. Thus, there is an urgent need to find new therapeutic approaches such as matrix therapy replacement. To determine the efficacy of a new ophthalmic treatment (Clerapliq^®) for SCCEDs and ulcerative keratitis associated with bullous keratopathy, a total of 11 dogs referred to the clinic because of nonhealing erosive ulcers after a classic primary treatment were enrolled to get this new treatment. Dogs underwent ophthalmic exams and 7 dogs (10 eyes) were diagnosed with superficial ulceration and 4 dogs (5 eyes) with bullous keratopathy due to endothelial dystrophy/degeneration. They received eye drops of Clerapliq^® every 3 days until recovery. The results showed that the corneas with recurrences of the ulcers were resolved predominantly by using Clerapliq^® every 3 days in 83.3% of the cases during a period of treatment ranging between 6 to 35 days. Therefore, this new approach using matrix therapy regenerating technology in treating superficial ulcers and bullous keratopathy in dogs can be successfully considered as an adjunctive therapy.

Clinical trial of adjunctive autologous platelet-rich plasma treatment following diamond-burr debridement for spontaneous chronic corneal epithelial defects in dogs

OBJECTIVE To evaluate the effects of adjunctive treatment with autologous platelet-rich plasma (PRP) on corneal reepithelialization, vascularization, and fibrosis in dogs with spontaneous chronic corneal epithelial defects (SCCEDs). DESIGN Randomized, controlled, double-masked clinical trial. ANIMALS 40 client-owned dogs with uncomplicated SCCEDs. PROCEDURES All dogs were treated with diamond-burr epithelial debridement (DBD) of affected eyes, topical tobramycin solution and atropine sulfate ointment application, and Elizabethan collar placement for 4 weeks. Dogs were randomly assigned to topical ocular administration of autologous PRP (n = 20) or artificial tear solution (control group; 20) 4 times daily for 28 days. Recheck examinations were performed approximately 2 and 4 weeks after treatment began to evaluate SCCEDs for corneal reepithelialization, and semiquantitative corneal vascularization and corneal fibrosis scores were assigned according to affected corneal surface area. Results were compared between groups. RESULTS All dogs completed the study. The SCCEDs had completely reepithelialized in 11 (55%) control dogs and 12 (60%) PRP-treated dogs by the 2-week reevaluation, and in 15 (75%) control dogs and 18 (90%) PRP-treated dogs by the 4-week reevaluation. No significant differences were identified between groups in these proportions nor in mean differences from pretreatment scores for corneal vascularization and fibrosis. CONCLUSIONS AND CLINICAL RELEVANCE In this preliminary study involving dogs with uncomplicated SCCEDs, topical PRP administered as an adjunctive treatment following DBD had no significant effect on healing. A larger study is warranted to support or refute these findings and to determine the effects of adjunctive PRP treatment for dogs with complicated SCCEDs.

Susceptibilidade antibiótica de isolados bacterianos em diferentes tipos de ceratites ulcerativas de cães na cidade de Cuiabá

RESUMO: Objetivou-se identificar microrganismos isolados de diferentes tipos de ceratite ulcerativa em cães, juntamente com a sua susceptibilidade a antimicrobianos. O resultado do tratamento médico e cirúrgico também foi correlacionado com o tipo de isolado. Amostras para microbiologia foram obtidas com auxílio de swab estéril em 104 olhos de 72 pacientes sem histórico prévio de tratamento com antibióticos tópicos, atendidos no período de maio de 2012 a março de 2015. Os antibióticos testados foram: neomicina, gentamicina, tobramicina, cloranfenicol, polimixina B, ciprofloxacino, ofloxacino e moxifloxacina. No total, 131 bactérias foram isoladas de 96/104 olhos estudados, sendo o gênero Staphylococcus (48,09%) predominante, seguido por Pseudomonas aeruginosa (16,01%). O Shih Tzu foi a raça mais prevalente (33,33%) e o número de isolados gram-negativos foi significativamente maior nessa raça, comparativamente aos Pinschers (p=0,003), aos Filas, aos Poodles e aos sem raça definida (p=0,046). As bactérias isoladas neste estudo apresentaram maior susceptibilidade ao ofloxacino (84,55%), que foi significativamente mais eficaz em relação a neomicina e a polimixina B (p<0,0001), ao cloranfenicol (p=0,0001), a tobramicina (p=0,0007), a gentamicina (p=0,0021) e as outras fluorquinolonas, ciprofloxacino (p=0,0004) e moxifloxacino (p<0,0001). Os organismos gram-positivos foram isolados de um número significativamente maior de olhos que apresentavam ceratite ulcerativa não complicada, comparativamente àqueles com olhos acometidos por ceratite ulcerativa complicada (p=0,011). Igualmente, o número de bactérias gram-positivas foi maior que o de gram-negativas, tanto nos casos que receberam tratamento médico, como nos que foram operados, sem significativa estatística (p=0,745). Na presente pesquisa, Staphylococcus sp. foi a bactéria mais encontrada nas ceratites ulcerativas não complicadas. Já nos olhos com ceratites complicadas, embora a Pseudomonas aeruginosa tenha sido a bactéria mais predominante, o tratamento clínico foi suficiente para cura da afecção corneal na maior parte dos casos. O ofloxacino e a gentamicina foram os agentes mais eficazes contra a maioria dos isolados, com exceção do Streptococcus sp., onde o cloranfenicol se mostrou o mais eficaz. Ceratites ulcerativas sem complicações que apresentem culturas negativas podem evoluir para ceratites ulcerativas complicadas, salientando a necessidade de tratamento anti-colagenolítico em todos os casos.

Involvement of NADPH oxidases in alkali burn-induced corneal injury

Chemical burns are a major cause of corneal injury. Oxidative stress, inflammatory responses and neovascularization after the chemical burn aggravate corneal damage, and lead to loss of vision. Although NADPH oxidases (Noxs) play a crucial role in the production of reactive oxygen species (ROS), the role of Noxs in chemical burn-induced corneal injury remains to be elucidated. In the present study, the transcription and expression of Noxs in corneas were examined by RT-qPCR, western blot analysis and immunofluorescence staining. It was found that alkali burns markedly upregulated the transcription and expression of Nox2 and Nox4 in human or mouse corneas. The inhibition of Noxs by diphenyleneiodonium (DPI) or apocynin (Apo) effectively attenuated alkali burn-induced ROS production and decreased 3-nitrotyrosine (3-NT) protein levels in the corneas. In addition, Noxs/CD11b double-immunofluorescence staining indicated that Nox2 and Nox4 were partially co-localized with CD11b. DPI or Apo prevented the infiltration of CD11b-positive inflammatory cells, and inhibited the transcription of inflammatory cytokines following alkali burn-induced corneal injury. In our mouse model of alkali burn-induced corneal injury, corneal neovascularization (CNV) occurred on day 3, and it affected 50% of the whole area of the cornea on day 7, and on day 14, CNV coverage of the cornea reached maximum levels. DPI or Apo effectively attenuated alkali burn-induced CNV and decreased the mRNA levels of angiogenic factors, including vascular endothelial growth factor (VEGF), VEGF receptors and matrix metalloproteinases (MMPs). Taken together, our data indicate that Noxs play a role in alkali burn-induced corneal injury by regulating oxidative stress, inflammatory responses and CNV, and we thus suggest that Noxs are a potential therapeutic target in the future treatment of chemical-induced corneal injury.

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.

Involvement of YAP, TAZ and HSP90 in contact guidance and intercellular junction formation in corneal epithelial cells

The extracellular environment possesses a rich milieu of biophysical and biochemical signaling cues that are simultaneously integrated by cells and influence cellular phenotype. Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (WWTR1; TAZ), two important signaling molecules of the Hippo pathway, have been recently implicated as nuclear relays of cytoskeletal changes mediated by substratum rigidity and topography. These proteins intersect with other important intracellular signaling pathways (e.g. Wnt and TGFβ). In the cornea, epithelial cells adhere to the stroma through a 3-dimensional topography-rich basement membrane, with features in the nano-submicron size-scale that are capable of profoundly modulating a wide range of fundamental cell behaviors. The influences of substratum-topography, YAP/TAZ knockdown, and HSP90 inhibition on cell morphology, YAP/TAZ localization, and the expression of TGFβ2 and CTGF, were investigated. The results demonstrate (a) that knockdown of TAZ enhances contact guidance in a YAP dependent manner, (b) that CTGF is predominantly regulated by YAP and not TAZ, and (c) that TGFβ2 is regulated by both YAP and TAZ in these cells. Additionally, inhibition of HSP90 resulted in nuclear localization and subsequent transcriptional-activation of YAP, formation of cell-cell junctions and co-localization of E-cadherin and β-catenin at adherens junctions. Results presented in this study reflect the complexities underlying the molecular relationships between the cytoskeleton, growth factors, heat shock proteins, and co-activators of transcription that impact mechanotransduction. The data reveal the importance of YAP/TAZ on the cell behaviors, and gene and protein expression.

Effect of corneal contact lens wear on healing time and comfort post LGK for treatment of SCCEDs in boxers

PURPOSE

To determine whether dogs with spontaneous chronic corneal epithelial defects (SCCEDs) would heal faster and with an improved comfort score following linear grid keratotomy (LGK) combined with corneal contact lens (Acrivet(™) ) wear when compared to dogs having the LGK procedure alone.

STUDY DESIGN

Prospective study.

METHODS

Twenty-seven boxer dogs (27 eyes) diagnosed with a SCCEDs were enrolled in the study. A LGK was performed on all dogs under dexmedetomidine and butorphanol sedation. Fourteen eyes were randomly assigned to receive a corneal contact lens. The dogs were evaluated typically at 7, 10, and 14 days or until the ulceration was healed. Client surveys were completed by the owners to subjectively assess comfort level and contact lens retention. Statistical analyses were performed utilizing generalized linear models and survival analysis with the Wilcoxon-Gehan test to evaluate group differences.

RESULTS

All ulcers healed after the LGK procedure. Dogs with bandage contact lenses had a statistically significant (P = 0.035) decrease in median healing time (7 days (95% CI [7,9]) compared to those without contact lenses (10 days (95% CI [7,12])). There was no difference in subjective comfort score between treatment groups. Early contact loss occurred in 28.6% (95% CI [8.4%, 58.1%]) of dogs. All of the Acrivet(™) ruler corneal measurements agreed to within 1 mm (95% CI [87.2%, 100%]) of the Jameson caliper measurements of horizontal corneal diameter.

CONCLUSIONS

The use of corneal bandage contact lenses significantly decreased median healing time although there was no effect on subjective comfort score. The Acrivet(™) ruler measurements were accurate in determining corneal diameter and therefore contact lens size.

Epigalloccatechin-3-gallate inhibits ocular neovascularization and vascular permeability in human retinal pigment epithelial and human retinal microvascular endothelial cells via suppression of MMP-9 and VEGF activation

Epigalloccatechin-3-gallate (EGCG) is the main polyphenol component of green tea (leaves of Camellia sinensis). EGCG is known for its antioxidant, anti-inflammatory, antiviral, and anti-carcinogenic properties. Here, we identify EGCG as a new inhibitor of ocular angiogenesis and its vascular permeability. Matrix metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF) play a key role in the processes of extracellular matrix (ECM) remodeling and microvascular permeability during angiogenesis. We investigated the inhibitory effects of EGCG on ocular neovascularization and vascular permeability using the retina oriented cells and animal models induced by VEGF and alkaline burn. EGCG treatment significantly decreased mRNA and protein expression levels of MMP-9 in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA) and tumor necrosis factor alpha (TNF-α) in human retinal pigment epithelial cells (HRPECs). EGCG also effectively protected ARPE-19 cells from cell death and attenuated mRNA expressions of key angiogenic factors (MMP-9, VEGF, VEGF Receptor-2) by inhibiting generation of reactive oxygen species (ROS). EGCG significantly inhibited proliferation, vascular permeability, and tube formation in VEGF-induced human retinal microvascular endothelial cells (HRMECs). Furthermore, EGCG significantly reduced vascular leakage and permeability by blood-retinal barrier breakdown in VEGF-induced animal models. In addition, EGCG effectively limited upregulation of MMP-9 and platelet endothelial cell adhesion molecule (PECAM/CD31) on corneal neovascularization (CNV) induced by alkaline burn. Our data suggest that MMP-9 and VEGF are key therapeutic targets of EGCG for treatment and prevention of ocular angiogenic diseases such as age-related macular degeneration, diabetic retinopathy, and corneal neovascularization.

The beneficial effects of doxycycline, an inhibitor of matrix metalloproteinases, on sulfur mustard-induced ocular pathologies depend on the injury stage

PURPOSE

Sulfur mustard (SM) induces acute ocular lesions, including erosions and inflammation that may be followed by delayed injuries expressed by epithelial defects and neovascularization (NV). Based on the matrix metalloproteinases (MMPs) activity, we evaluated the clinical and biochemical effects of topical treatment with doxycycline, an MMP inhibitor, targeted to the various injury stages.

METHODS

Rabbit eyes were exposed to SM vapor. A clinical follow-up was carried out up to 2 months. Tear fluid and cornea samples were collected at different time points for measurements of MMPs activity by zymography. Efficacy of a post-exposure topical doxycycline (2 mg/ml in phosphate buffer saline, ×4/d), targeted to the different phases of the clinical injury, was evaluated.

RESULTS

Elevated MMP-9 and MMP-2 activities were found in all corneas during the acute injury and in vascularized corneas during the delayed pathology. In the tear fluid, high MMP-9 activity and negligible MMP-2 activity were found in all the exposed eyes until after the appearance of the delayed pathology symptoms. Prolonged doxycycline treatment reduced MMP-9 activity in the tear fluid. During the acute phase, doxycycline treatment reduced corneal MMP-9 activity and the severity of the injury. Targeting the delayed pathology, doxycycline was clinically efficient only when treatment began before NV appearance.

CONCLUSIONS

This in vivo study showed the involvement of MMP-9 and MMP-2 during different phases of the SM-induced ocular injury, and the potential of doxycycline treatment as a post exposure measure for reducing the acute injury and as a preventive therapy for ameliorating the delayed pathology. The tear fluid provided a non-invasive method for continuous follow-up of MMPs activity and revealed additional beneficial aspects of injury and the treatment.

Contributions of ocular surface components to matrix-metalloproteinases (MMP)-2 and MMP-9 in feline tears following corneal epithelial wounding

Purpose

This study investigated ocular surface components that contribute to matrix-metalloproteinase (MMP)-2 and MMP-9 found in tears following corneal epithelial wounding.

Methods

Laboratory short-haired cats underwent corneal epithelial debridement in one randomly chosen eye (n = 18). Eye-flush tears were collected at baseline and during various healing stages. Procedural control eyes (identical experimental protocol as wounded eyes except for wounding, n = 5) served as controls for tear analysis. MMP activity was analyzed in tears using gelatin zymography. MMP staining patterns were evaluated in ocular tissues using immunohistochemistry and used to determine MMP expression sites responsible for tear-derived MMPs.

Results

The proMMP-2 and proMMP-9 activity in tears was highest in wounded and procedural control eyes during epithelial migration (8 to 36 hours post-wounding). Wounded eyes showed significantly higher proMMP-9 in tears only during and after epithelial restratification (day 3 to 4 and day 7 to 28 post-wounding, respectively) as compared to procedural controls (p<0.05). Tears from wounded and procedural control eyes showed no statistical differences for pro-MMP-2 and MMP-9 (p>0.05). Immunohistochemistry showed increased MMP-2 and MMP-9 expression in the cornea during epithelial migration and wound closure. The conjunctival epithelium exhibited highest levels of both MMPs during wound closure, while MMP-9 expression was reduced in conjunctival goblet cells during corneal epithelial migration followed by complete absence of the cells during wound closure. The immunostaining for both MMPs was elevated in the lacrimal gland during corneal healing, with little/no change in the meibomian glands. Conjunctival-associated lymphoid tissue (CALT) showed weak MMP-2 and intense MMP-9 staining.

Conclusions

Following wounding, migrating corneal epithelium contributed little to the observed MMP levels in tears. The major sources assessed in the present study for tear-derived MMP-2 and MMP-9 following corneal wounding are the lacrimal gland and CALT. Other sources included stromal keratocytes and conjunctiva with goblet cells.

Minocycline inhibits alkali burn-induced corneal neovascularization in mice

The purpose of this study was to investigate the effects of minocycline on alkali burn-induced corneal neovascularization (CNV). A total of 105 mice treated with alkali burns were randomly divided into three groups to receive intraperitoneal injections of either phosphate buffered saline (PBS) or minocycline twice a day (60 mg/kg or 30 mg/kg) for 14 consecutive days. The area of CNV and corneal epithelial defects was measured on day 4, 7, 10, and14 after alkali burns. On day 14, a histopathological examination was performed to assess morphological change and the infiltration of polymorphonuclear neutrophils (PMNs). The mRNA expression levels of vascular endothelial growth factor (VEGF) and its receptors (VEGFRs), basic fibroblast growth factor (bFGF), matrix metalloproteinases (MMPs), interleukin-1α, 1β, 6 (IL-1α, IL-1β, IL-6) were analyzed using real-time quantitative polymerase chain reaction. The expression of MMP-2 and MMP-9 proteins was determined by gelatin zymography. In addition, enzyme-linked immunosorbent assay was used to analyze the protein levels of VEGFR1, VEGFR2, IL-1β and IL-6. Minocycline at a dose of 60 mg/kg or 30 mg/kg significantly enhanced the recovery of the corneal epithelial defects more than PBS did. There were significant decreases of corneal neovascularization in the group of high-dosage minocycline compared with the control group at all checkpoints. On day 14, the infiltrated PMNs was reduced, and the mRNA expression of VEGFR1, VEGFR2, bFGF, IL-1β, IL-6, MMP-2, MMP-9, -13 as well as the protein expression of VEGFR2, MMP-2, -9, IL-1β, IL-6 in the corneas were down-regulated with the use of 60 mg/kg minocycline twice a day. Our results showed that the intraperitoneal injection of minocycline (60 mg/kg b.i.d.) can significantly inhibit alkali burn-induced corneal neovascularization in mice, possibly by accelerating corneal wound healing and by reducing the production of angiogenic factors, inflammatory cytokines and MMPs.

A comparison of basal and eye-flush tears for the analysis of cat tear proteins

PURPOSE

To identify a rapid and effective tear collection method providing sufficient tear volume and total protein content (TPC) for analysis of individual proteins in cats.

METHODS

Domestic adult short-haired cats (12-37 months; 2.7-6.6 kg) were used in the study. Basal tears without stimulation and eye-flush tears after instillation of saline (10 μl) were collected using microcapillary tubes from animal eyes either unwounded control or wounded with 9-mm central epithelial debridement giving four groups with n = 3. Tear comparisons were based on total time and rate for tear collection, TPC using micro bicinchoninic acid (BCA), tear immunoglobulin A (IgA), total matrix-metalloproteinase (MMP)-9 concentration using sandwich enzyme-linked immunosorbent assay (ELISA) and MMP-9 activity.

RESULTS

Eye-flush tears were collected significantly faster than basal tears in wounded eyes with higher rates for tear collection in unwounded control and wounded eyes. TPC was significantly lower in eye-flush tears compared to basal tears. The relative proportion of tear IgA normalized to TPC (% IgA of TPC) was not significantly different between basal and eye-flush tears. In unwounded control eyes, MMP-9 was slightly higher in eye-flush than in basal tears; activity of MMP-9 in both tear types was similar. In wounded eyes, eye-flush tears showed highest MMP-9 levels and activity on Day 1, which subsequently decreased to Day 7. MMP-9 activity in basal tears from wounded eyes did not display changes in expression.

CONCLUSIONS

Eye-flush tears can be collected rapidly providing sufficient tear volume and TPC. This study also indicates that eye-flush tears may be more suitable than basal tears for the analysis of MMPs following corneal wounding.

In vivo effects of adjunctive tetracycline treatment on refractory corneal ulcers in dogs

OBJECTIVE

To evaluate effect of adjunctive treatment with tetracycline analogues on time to complete corneal reepithelialization in dogs with nonhealing (ie, refractory) corneal ulcers.

DESIGN

Randomized controlled clinical trial.

ANIMALS

89 dogs with refractory corneal ulcers.

PROCEDURES

Corneal ulcers were treated via debridement and grid keratotomy. Dogs were assigned to receive 1 of 3 treatment regimens for up to 6 weeks: doxycycline (5 mg/kg [2.27 mg/lb], PO, q 12 h) with topically applied ophthalmic ointment containing neomycin, polymyxin B, and bacitracin (ie, triple antibiotic ointment; q 8 h); cephalexin (22 mg/kg [10 mg/lb], PO, q 12 h) with topically applied oxytetracycline ophthalmic ointment (q 8 h); or a control treatment of cephalexin (22 mg/kg, PO, q 12 h) with topically applied triple antibiotic ointment (q 8 h). Healing was monitored via measurements of the wound with calipers and evaluation of photographs obtained every 2 weeks. Treatment effectiveness was evaluated by wound healing and decreased signs of pain.

RESULTS

The Boxer breed was overrepresented in all groups. At the 2-week time point, wound healing was significantly more common in small-breed dogs, compared with large-breed dogs. Dogs treated with oxytetracycline ophthalmic ointment had a significantly shorter healing time than did dogs receiving the control treatment. Corneal ulcers in dogs that received doxycycline PO healed more rapidly than did ulcers in dogs in the control treatment group; however, this difference was not significant.

CONCLUSIONS AND CLINICAL RELEVANCE

Topical tetracycline ophthalmic ointment was a safe, inexpensive, and effective adjunctive treatment for refractory corneal ulcers in dogs.

Immunohistochemical study of matrix metalloproteinases-2 and -9, macrophage inflammatory protein-2 and tissue inhibitors of matrix metalloproteinases-1 and -2 in normal, purulonecrotic and fungal infected equine corneas

OBJECTIVE

Determine the effects of matrix metalloproteinases (MMPs)-2, -9, macrophage inflammatory protein-2 (MIP-2), tissue inhibitors of matrix metalloproteinase (TIMP)-1 and -2 by immunohistochemical expression in fungal affected and purulonecrotic corneas.

PROCEDURE

Paraffin-embedded equine corneal samples; normal (n = 9), fungal affected (FA; n = 26), and purulonecrotic without fungi (PN; n = 41) were evaluated immunohistochemically for MMP-2, -9, MIP-2, TIMP-1 and -2. The number of immunoreactive inflammatory cells was counted and statistics analyzed. Western blot was performed to detect MMP-2, MMP-9, TIMP-1 and TIMP-2 proteins.

RESULTS

Matrix metalloproteinases-2, -9, MIP-2, TIMP-1 and -2 immunoreactivity was identified in corneal epithelium of normal corneas, and in corneal epithelium, inflammatory cells, keratocytes, and vascular endothelial cells of both FA and PN samples. Inflammatory cell immunoreactivity was significantly higher in FA and PN samples than in the normal corneas. There was positive correlation between MMP-2 and MIP-2, MMP-9 and MIP-2, and MMP-9 and TIMP-1 in inflammatory cell immunoreactivity in FA samples. There was positive correlation between MMP-9 and MIP-2, MMP-9 and TIMP-2, MIP-2 and TIMP-1, and MIP-2 and TIMP-2 in inflammatory cell immunoreactivity in PN samples. Western blot confirmed the presence of all four proteins in equine corneal samples.

CONCLUSION

Increased immunoreactivity of MMP-2 and -9 in FA and PN samples is indirectly related to MIP-2 through its role in neutrophil chemo-attraction. Tissue inhibitors of matrix metalloproteinase-1 and TIMP-2 are up-regulated in equine purulonecrotic and fungal keratitis secondary to MMP-2 and MMP-9 expression. The correlation between MMPs -2 and -9, MIP-2, TIMPs -1 and -2 suggests that these proteins play a specific role in the pathogenesis of equine fungal keratitis.

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.