Evaluation of various compounds to inhibit activity of matrix metalloproteinases in the tear film of horses with ulcerative keratitis

Extracellular Vesicles Isolated from Equine Adipose-Derived Stromal Stem Cells (ASCs) Mitigate Tunicamycin-Induced ER Stress in Equine Corneal Stromal Stem Cells (CSSCs)

Corneal ulcers, characterized by severe inflammation of the cornea, can lead to serious, debilitating complications and may be vision-threatening for horses. In this study, we aimed to investigate the role of endoplasmic reticulum (ER) stress in corneal stem progenitor cell (CSSC) dysfunction and explore the potential of equine adipose-derived stromal stem cell (ASC)-derived extracellular vesicles (EVs) to improve corneal wound healing. We showed that CSSCs expressed high levels of CD44, CD45, and CD90 surface markers, indicating their stemness. Supplementation of the ER-stress-inducer tunicamycin to CSSCs resulted in reduced proliferative and migratory potential, accumulation of endoplasmic reticulum (ER)-stressed cells in the G0/G1 phase of the cell cycle, increased expression of proinflammatory genes, induced oxidative stress and sustained ER stress, and unfolded protein response (UPR). Importantly, treatment with EVs increased the proliferative activity and number of cells in the G2/Mitosis phase, enhanced migratory ability, suppressed the overexpression of proinflammatory cytokines, and upregulated the anti-inflammatory miRNA-146a-5p, compared to control and/or ER-stressed cells. Additionally, EVs lowered the expression of ER-stress master regulators and effectors (PERK, IRE1, ATF6, and XBP1), increased the number of mitochondria, and reduced the expression of Fis-1 and Parkin, thereby promoting metabolic homeostasis and protecting against apoptosis in equine CSSCs. Our findings demonstrate that MSCs-derived EVs represent an innovative and promising therapeutic strategy for the transfer of bioactive mediators which regulate various cellular and molecular signaling pathways.

In Vitro Antimicrobial Activity of N-Acetylcysteine against Pathogens Most Commonly Associated with Infectious Keratitis in Dogs and Cats

To determine the in vitro antimicrobial activity of N-acetylcysteine (NAC) against common pathogens associated with infectious keratitis in dogs and cats, clinical isolates of Staphylococcus (S.) pseudintermedius (n = 20), Streptococcus (St.) canis (n = 10) and Pseudomonas (P.) aeruginosa (n = 7) of canine and feline infectious ulcerative keratitis and a quality control strain (P. aeruginosa DSM 19880) were tested. The minimal inhibitory concentration (MIC) of NAC concentrations was determined using microdilution methodology. For S. pseudintermedius and P. aeruginosa, NAC concentrations in the range of 1.56 mg/mL (0.156%) to 100 mg/mL (10%), and for St. canis, concentrations ranging from 0.195 mg/mL (0.0195%) to 6.25 mg/mL (0.625%) were tested. For S. pseudintermedius, the MIC was 3.12 mg/mL (0.312%) for all tested isolates. For P. aeruginosa isolates and the quality control strain, the MIC ranged from 3.12 mg/mL (0.312%) to 6.25 mg/mL (0.625%). For St. canis, the MIC ranged from 1.56 mg/mL (0.156%) to 3.12 mg/mL (0.312%). NAC has an in vitro antimicrobial activity against three bacterial species commonly found in infectious keratitis in dogs and cats and therefore may be a promising alternative or adjuvant to topical antibiotics. The results warrant a clinical pilot study to assess the potential of NAC to reduce or replace the use of topical antibiotics in line with the One Health approach.

The bactericidal effect of two photoactivated chromophore for keratitis-corneal crosslinking protocols (standard vs. accelerated) on bacterial isolates associated with infectious keratitis in companion animals

Background

Bacterial corneal infections are common and potentially blinding diseases in all species. As antibiotic resistance is a growing concern, alternative treatment methods are an important focus of research. Photoactivated chromophore for keratitis-corneal crosslinking (PACK-CXL) is a promising oxygen radical-mediated alternative to antibiotic treatment. The main goal of this study was to assess the anti-bactericidal efficacy on clinical bacterial isolates of the current standard and an accelerated PACK-CXL treatment protocol delivering the same energy dose (5.4 J/cm²).

Methods

Clinical bacterial isolates from 11 dogs, five horses, one cat and one guinea pig were cultured, brought into suspension with 0.1% riboflavin and subsequently irradiated. Irradiation was performed with a 365 nm UVA light source for 30 min at 3mW/cm² (standard protocol) or for 5 min at 18mW/cm² (accelerated protocol), respectively. After treatment, the samples were cultured and colony forming units (CFU’s) were counted and the weighted average mean of CFU’s per μl was calculated. Results were statistically compared between treated and control samples using a linear mixed effects model.

Results

Both PACK-CXL protocols demonstrated a significant bactericidal effect on all tested isolates when compared to untreated controls. No efficacy difference between the two PACK-CXL protocols was observed.

Conclusion

The accelerated PACK-CXL protocol can be recommended for empirical use in the treatment of bacterial corneal infections in veterinary patients while awaiting culture results. This will facilitate immediate treatment, the delivery of higher fluence PACK-CXL treatment within a reasonable time, and minimize the required anesthetic time or even obviate the need for general anesthesia.

Dorsally placed commercially available subpalpebral lavage systems have low complication rates in horses

OBJECTIVE

To retrospectively evaluate the complication rate following dorsal placement of a commercially available 1-hole subpalpebral lavage system (SPL) at a veterinary teaching hospital.

ANIMALS

102 client-owned horses with ophthalmic disease.

PROCEDURES

Medical records of horses (2010 to 2020) with ophthalmic disease were reviewed to determine whether a commercially available SPL system was dorsally placed. Data collected from the medical record included signalment, presenting complaint(s), diagnosis, ophthalmic procedures performed, SPL laterality, hospital service that placed the SPL, anesthetic technique for placement (general anesthesia or sedation with local nerve blocks), duration of SPL management while hospitalized or at home, type of enclosure for the horse, use of eye protection, duration of time the SPL was in place, location of SPL management (home vs hospital), types and numbers of medications administered, recorded complications, and outcome of the globe. Complications experienced during treatment were categorized as either ocular or nonocular. The χ2 test for independence test and Fisher exact test were performed to examine the relationship between the department that placed the SPL, method of anesthesia, antimicrobial administration, type of facial protection used, and complication type and rate.

RESULTS

Overall complication rate for SPL systems was 29.1% (37/127), with 21.2% (27/127) being ocular complications and 7.9% (10/127) being nonocular complications. SPL complication rate was not affected by any variable that was examined.

CLINICAL RELEVANCE

Commercially available SPL systems placed dorsally have a low ocular complication rate. These SPL systems may be placed by veterinarians with varied training backgrounds and managed at home without significantly increasing complication rate.

Determining the efficacy of the bovine amniotic membrane homogenate during the healing process in rabbits' ex vivo corneas

OBJECTIVE

To evaluate the efficacy of bovine amniotic membrane homogenate (BAMH) on wounded ex vivo rabbit corneas.

PROCEDURE

Eighteen corneas obtained from normal rabbit eyes were wounded equally using a 6 mm trephine and cultured into an air-liquid interface model. Corneas were treated with phosphate-buffered saline (PBS) (n = 6, control group), 0.2% ethylenediaminetetraacetic acid (EDTA; n = 6), or BAMH (n = 6). All treatments were applied topically 6 times/day. Each cornea was macrophotographed daily with and without fluorescein stain to assess epithelialization and haziness. After 7 days, corneal transparency was evaluated, and the tissues prepared for histologic analysis of viability, and total and epithelial thickness.

RESULTS

The mean epithelialization time was 6.2 ± 0.82 days for the control group, 6.2 ± 0.75 days for the EDTA-treated group, and 5.1 ± 0.40 days for the BAMH-treated group, demonstrating a significant difference between the BAMH and the other groups. The corneas that received EDTA had better transparency compared with the other groups. Histologically, all corneas had adequate morphology and architecture after healing. Analysis of corneal and epithelial thickness revealed no significant difference among groups.

CONCLUSION

Bovine amniotic membrane homogenate is an effective and promising treatment for stromal and epithelial ulcers.

Genipin Delays Corneal Stromal Enzymatic Digestion

Purpose

To evaluate the use of genipin in delaying enzymatic digestion of corneal stroma.

Methods

Human corneal stromal tissue was treated with genipin, a known chemical crosslinker, and then along with control tissue was subjected to enzymatic digestion with collagenase. The effects of genipin treatment in retarding stromal digestion were analyzed with phase contrast microscopy, a protein quantification assay, second harmonic generation imaging, and transmission electron microscopy.

Results

Genipin increased stromal resistance to enzymatic digestion when compared with untreated stroma. A morphologic analysis and protein quantification showed increased stromal resistance to enzymatic digestion once stromal tissue was treated with genipin. Second harmonic generation imaging revealed persistent fibrillar collagen signaling in genipin-treated tissue in contrast with untreated tissue suggesting that genipin retards collagenolysis.

Conclusions

Genipin increases stromal resistance to enzymatic digestion in controlled experiments as demonstrated by protein quantification studies and through morphologic imaging.

Translational Relevance

This study explores the novel use of genipin in delaying enzymatic stromal digestion. Delaying stromal melting in the setting of corneal infectious or autoimmune keratitis can potentially decrease clinical morbidity.

The role of topical N-acetylcysteine in ocular therapeutics

N-acetylcysteine (NAC) was first discovered as a mucolytic agent in 1960. We investigate the role of topical NAC in ocular therapeutics, including its mechanism of action, current applications, and adverse effects. A systematic search of peer-reviewed articles identified 106 references including in vitro, in vivo and clinical studies on the use of NAC in the treatment of ocular diseases. NAC can be synthetically manufactured, and its mechanisms of action include mucolysis, scavenging hydroxyl radicals, and modulation of inflammatory cascades. These unique properties contribute to the diverse applications of NAC, including its steroid-sparing potential. NAC has been used topically in the treatment of corneal wounds, chemical injuries, keratitis, dry eye disease and meibomian gland dysfunction. The clinical benefits of NAC are evident over a wide range of concentrations, the most common being 5-10% topical NAC applied four times daily. Adverse effects such as corneal necrosis are rare, but have been reported with higher doses. NAC also has potential applications in laser epithelial keratomileusis, diabetic eye disease, retinitis pigmentosa, senile nuclear cataracts, macular degeneration, and cigarette smoke-induced corneal damage. Recently, chitosan-NAC has been used as a nanocarrier for the topical administration of medications to the ocular surface. Owing to its potent antioxidant, anti-inflammatory and mucolytic properties, topical NAC has had extensive use in the treatment of ocular pathology.

Determining MMP-2 and MMP-9 reductive activities of bovine and equine amniotic membranes homogenates using fluorescence resonance energy transfer

INTRODUCTION

Matrix metalloproteinases (MMPs)-2 and -9 are present in corneal ulcers, and an imbalance between MMPs and tissue inhibitors of metalloproteinases (TIMPs) leads to further corneal degradation. Amniotic membrane homogenate (AMH) has proteolytic properties beneficial for corneal healing, but it is unknown whether AMH possesses TIMPs or effectively inhibits MMP-2 and MMP-9 activity.

OBJECTIVE

To determine if bovine and equine AMH reduce in vitro MMP-2 and MMP-9 activities associated with the presence of TIMPs.

PROCEDURES

Undiluted and diluted twofold series (0-fold to 16-fold dilutions) of equine amniotic membrane homogenates (EAMH, n = 8) and bovine amniotic membrane homogenates (BAMH, n = 8) were subjected to fluorescence resonance energy transfer, and the fluorescence emitted was recorded over time. Average fluorescence was calculated versus recombinant concentration. Enzyme-linked immunosorbent assays for TIMPs 1-4 were applied to quantify TIMPs in the samples.

RESULTS

AMH from both species were able to inhibit MMP-2 and MMP-9 activities in vitro, and the inhibition efficacy decreased gradually with dilution. BAMH was significantly more effective than EAMH at inhibiting MMP-2 and MMP-9 in vitro. TIMPs -2 and -3 were present in EAMH and BAMH. TIMP-1 was detected only in BAMH, and TIMP-4 was not detected in any samples.

CONCLUSION

Both EAMH and BAMH directly inhibited MMP-2 and MMP-9 in vitro without dilution, and BAMH showed better inhibition of MMP-2 and MMP-9 before and after dilution compared to EAMH.

Quantitative Chemical Proteomics Reveals Resveratrol Inhibition of A549 Cell Migration Through Binding Multiple Targets to Regulate Cytoskeletal Remodeling and Suppress EMT

Resveratrol (RSV), a health-promoting natural product, has been shown to affect various cellular processes in tumor cells. However, the specific protein targets of RSV and the mechanism of action (MOA) of its anticancer effect remain elusive. In this study, the pharmacological activity of RSV was first evaluated in A549 cells, and the results showed that RSV significantly inhibited A549 cell migration but did not affect cell viability. To elucidate the underlying mechanism, a quantitative chemical proteomics approach was employed to identify the protein targets of RSV. A total of 38 target proteins were identified, and proteomic analysis showed that the targets were mainly involved in cytoskeletal remodeling and EMT, which were verified by subsequent in vitro and in vivo assays. In conclusion, RSV inhibits A549 cell migration by binding to multiple targets to regulate cytoskeletal remodeling and suppress EMT.

Corneal Ulcer in Dogs and Cats: Novel Clinical Application of Regenerative Therapy Using Subconjunctival Injection of Autologous Platelet-Rich Plasma

Background: Corneal ulcer could be a major source of distress in small animals, with many contributing agents. In recent years, few studies evaluated the efficacy of platelet-rich plasma (PRP) in healing corneal ulcers. Aim: This study aimed to assess the ability of subconjunctival injection of autologous PRP in the treatment of corneal ulcers in dogs and cats as well as estimate the expression of matrix metalloproteinase (MMP)-2, MMP-9, and oxidative stress biomarkers in these patients. Methods: A total number of 28 animals (16 cats and 12 dogs) were enrolled in this study. Each animal was subjected to clinical, neurologic, and ophthalmic examinations where the type of ulcer was documented. Tear samples were collected for evaluation of oxidative biomarkers and MMPs; conjunctival swabs were taken to identify the involved organism. PRP was prepared from each animal and given as subconjunctival injection; numbers of injections were done according to case response. Clinical follow-up was done and documented for each case. Results: In cat patients, female and Persian cats were most affected; unilateral and superficial ulcers were most recorded. In male dogs, unilateral, and superficial ulcers were most recorded. FHV-1 was most identified in cats, while Staphylococcus aureus was most identified in dogs. Numbers of injections needed to achieve healing were recorded, with 50% of dogs needing two injections with 1-week intervals and 50% of cats needed three injections with 1-week intervals. Alterations in both oxidative biomarkers and MMPs were recorded in affected animals. Conclusion: The use of autologous PRP as a subconjunctival injection in treating corneal ulcers in dogs and cats is effective. The number of injections is the case and corneal ulcer type-dependent. Clinical Significance: Autologous PRP as a subconjunctival injection in treating corneal ulcer is a relatively cheap, safe method and can be done in the clinical setting.

Serum albumin and total protein concentration in the tear film of horses with healthy or diseased eyes

OBJECTIVE

To determine total protein content (TPC) and serum albumin levels in the tears of horses with healthy or diseased eyes.

ANIMALS STUDIED

Forty-two horses with healthy eyes and 11 horses with unilateral (n = 10) or bilateral (n = 1) ocular disease.

PROCEDURE

Each eye underwent an ophthalmic examination including detailed conjunctivitis scoring and tear collection with Schirmer strips. TPC and serum albumin levels were quantified in tear samples and compared among healthy eyes, affected eyes, and contralateral unaffected eyes. The impact of the following variables on lacrimal protein levels were assessed: age, breed, and sex (healthy eyes), as well as conjunctivitis score (diseased eyes).

RESULTS

Lacrimal TPC ranged from 7.0 to 19.5 mg/mL in healthy eyes, while serum albumin ranged from 71.1 to 711.3 µg/mL (~1.6% of TPC) and was higher in tears of aged and female horses (P ≤ .033). Eyes with ocular disease had significantly greater (P ≤ .001) serum albumin in tears (median 679.6 µg/mL) compared to contralateral unaffected eyes (130.0 µg/mL) and eyes of the reference population (200.7 µg/mL). However, lacrimal TPC did not differ significantly among the 3 groups. Scoring of palpebral conjunctival hyperemia trended toward a positive association with serum albumin in tears (r = 0.49, P = .062).

CONCLUSIONS

The protein profile in equine tears differs in health and disease. Serum albumin in tears increases with ocular disease and, similar to other species, might serve as a biomarker for ocular insult in horses. Future studies could investigate the protein levels in horses with specific ocular conditions and help determine the biological importance of albumin on the equine ocular surface.

Endothelial Safety and Efficacy of Ex Vivo Collagen Cross-linking of Human Corneal Transplants

PURPOSE

To assess endothelial safety and efficacy of ex vivo corneal collagen cross-linking (CXL) in human corneal transplants stored in 2 different culture media.

DESIGN

Fellow-eye controlled laboratory study of ex vivo human donor corneas.

METHODS

Three sets of paired human donor corneas, 5 pairs each, were stored in organ culture medium before deswelling either at 31 C or at room temperature. One eye of each pair was cross-linked by 0.1% riboflavin in hydroxylpropyl methylcellulose (HPMC) instillation for 10 minutes followed by 10 minutes of ultraviolet-A (9 mW/cm²) irradiation while contralateral eyes served as controls. In Set 1, endothelial cell densities were determined. In Set 2, paired samples were assigned to the 2 deswelling media and CXL efficacy was assessed comparing to untreated controls using collagenase-A-assisted enzymatic digestion. In Set 3, biomechanical testing was performed in the eye pairs (treated vs control) by stress/strain measurements.

RESULTS

There was no difference in endothelial cell counts between CXL samples and controls (P = .21). No statistically significant difference in digestion dynamics was found between tissues stored in the 2 different culture media. Complete enzymatic digestion was slowed down by 3 hours in the cross-linked samples (P = .036). Stress needed for a 12% strain was increased by 34% in the treatment group compared to control (P = .04).

CONCLUSIONS

Ex vivo CXL of human donor tissue is an effective and safe procedure with no difference regarding efficacy between 2 commercially available deswelling media. Biochemical and biomechanical resistance were significantly increased after CXL. Patients requiring keratoplasty owing to corneal melting might benefit from the strengthening effect of preoperative CXL of donor tissue.

In vitro assessment of the long-term stability of the inhibitory effects of canine and feline plasma on MMP 2 and 9

PURPOSE

To evaluate the effect of increasing storage time on the inhibitory effects of canine and feline plasma on matrix metalloproteinases (MMP) 2 and 9 in vitro.

METHODS

Matrix metalloproteinases 2 and 9 activity in the presence of canine plasma stored for 57, 155, 222, 316, 367, and 438 days, and feline plasma stored for 17, 198, 565, and 954 days was assayed using a commercially available colorimetric assay kit.

RESULTS

For canine plasma, the MMP 2 activity for older samples was not significantly different than the 57-day sample (P = 0.2025-0.9033). Two canine samples had significantly lower MMP 9 activity than the 57-day sample (367 days: P = 0.0099, 438 days: P = 0.0348, others P = 0.0778-0.9928). For feline plasma, storage time did not significantly affect inhibition of MMP 2 and MMP 9 activity (ANOVA, P = 0.2688 and P = 0.2404, respectively).

CONCLUSIONS

Increasing storage time does not significantly decrease the inhibiting activity of plasma on MMP 2 and 9 for up to 14 months in dogs and 31 months in cats.

Medical management of deep ulcerative keratitis in cats: 13 cases

CASE SERIES SUMMARY

Described are 13 cats diagnosed with deep ulcerative keratitis and successfully managed medically without grafting procedures. Typical treatment involved frequent topical application of serum and antibiotics (usually a fluoroquinolone and a cephalosporin). Seven cats also received systemic antibiotics. Analgesia was achieved using various combinations of topical atropine and systemic buprenorphine, robenacoxib or corticosteroids. Six cats were hospitalized for a median (range) period of 2.5 (1-8) days, typically because of frequent medication administration. Median (range) follow-up time was 41.5 (9-103) days. Median (range) number of recheck examinations was 4 (2-6). Median (range) time to corneal re-epithelialization was 21 (9-103) days. Median (range) topical antibiotic course was 29.5 (16-103) days. Median (range) duration of Elizabethan collar use was 28 (13-73) days. At the time of writing, no further recheck examinations were recommended for 10 cats; median (range) time between initial to final examinations in these cats was 35 (20-103) days. All cats retained the affected globes and were apparently comfortable and visual at the latest recheck examination.

RELEVANCE AND NOVEL INFORMATION

These cases reveal that aggressive medical management is highly successful in select cats with deep ulcerative keratitis, and can result in a cosmetically acceptable, apparently comfortable and visual globe. However, therapy is intensive with frequent administration of multiple topical and sometimes systemic medications, and requires multiple veterinary visits over many weeks. Referral to a veterinary ophthalmologist for consideration of surgical stabilization is recommended, as not all cases may be amenable to the medical therapy described here.

Equine Mesenchymal Stem Cells: Properties, Sources, Characterization, and Potential Therapeutic Applications

Properties like sustained multiplication and self-renewal, and homing and multilineage differentiation to undertake repair of the damaged tissues make stem cells the lifeline for any living system. Therefore, stem cell therapy is regarded to carry immense therapeutic potential. Though the dearth of understanding about the basic biological properties and pathways involved in therapeutic benefits currently limit the application of stem cells in humans as well as animals, there are innumerable reports that suggest clinical benefits of stem cell therapy in equine. Among various stem cell sources, currently adult mesenchymal stem cells (MSCs) are preferred for therapeutic application in horse owing to their easy availability, capacity to modulate inflammation, and promote healing. Also the cells carry very limited teratogenic risk compared to the pluripotent stem cells. Mesenchymal stem cells were earlier considered mainly for musculoskeletal tissues, but now may also be utilized in other diverse clinical problems in horse, and the results may be extrapolated even for human medicine. The current review highlights biological properties, sources, mechanisms, and potential therapeutic applications of stem cells in equine practice.

Impact of Flow Rate, Collection Devices, and Extraction Methods on Tear Concentrations Following Oral Administration of Doxycycline in Dogs and Cats

Purpose: Compare the precision of doxycycline quantification in tear fluid collected with either Schirmer strips or polyvinyl acetal (PVA) sponges following oral drug administration.

Methods: Three dogs and 3 cats were administered doxycycline orally at a dose of 4.2–5 mg/kg every 12 h for 6 consecutive days. At day 5 and 6, blood and tear fluid were sampled to capture doxycycline trough and maximal concentrations. Tear fluid was collected 3 times (spaced 10 min apart) at each session with the absorbent material placed in the lower conjunctival fornix until the 20-mm mark was reached (Schirmer strip, one eye) or for 1 min (PVA sponge, other eye). Tear extraction was performed with either centrifugation or elution in methanol. Doxycycline concentrations were measured with liquid chromatography–mass spectrometry. Low (100 ng/mL) and high (1,000 ng/mL) tear concentrations measured in vivo were spiked into each absorbent material in vitro to evaluate percentage drug recovery.

Results: After oral administration of doxycycline, the drug reached the tear compartment at concentrations of 45.1–900.7 ng/mL in cats and 45.4–632.0 ng/mL in dogs, representing a tear-to-serum ratio of 12% and 16%, respectively. Doxycycline tear concentrations were significantly more precise when tear collection was performed with Schirmer strips rather than PVA sponges (P = 0.007), but were not correlated with tear flow rate. In vitro doxycycline recovery was poor to moderate (<75%).

Conclusions: Schirmer strips represent a good option for lacrimal doxycycline quantification, although the collection and subsequent extraction have to be optimized to improve drug recovery.

Corneal Response to Injury and Infection in the Horse

This article describes the natural responses of the immune system and the cornea to injury and infection. The process of reepithelialization and reformation of stromal collagen is discussed, as are the clinical signs and manifestations of the effects of the healing response when it is routine and when it is pathologic. Excessive inflammatory or immune responses by host tissues can cause further damage that may be present from the antecedent injury or the effect of a pathogen. The clinical signs and manifestations of wound healing as well as potential therapeutic interventions are described.

Effects of topically applied heterologous serum on reepithelialization rate of superficial chronic corneal epithelial defects in dogs

OBJECTIVE To assess the effects of topical application of undiluted heterologous serum on time to corneal reepithelialization in dogs with superficial chronic corneal epithelial defects (SCCEDs). DESIGN Multicenter, randomized, double-masked, controlled clinical trial. ANIMALS 41 client-owned dogs. PROCEDURES After collection of baseline clinical and historical data, dogs were randomly assigned to receive topically applied undiluted heterologous serum (n = 22) or isotonic saline (0.9% NaCl) solution (19) along with tobramycin and atropine. Epithelial debridement (at all visits) and grid keratotomy (at visits 2, 3, and 4) of SCCEDs were performed. Ophthalmic examination including fluorescein application was performed once weekly for 4 weeks or until corneal reepithelialization. Clinicians and owners were masked to treatment group. RESULTS No differences in baseline data were detected between treatment groups. No difficulties with medication administration, noncompliance, or adverse reactions were noted. All SCCEDs in both groups healed by 4 weeks after treatment began. Median time to reepithelialization (2 weeks) was not significantly different between serum-treated and placebo-treated eyes. Irrespective of treatment group, median time to reepithelialization was not significantly different for Boxers versus non-Boxer breeds. Direct correlations were detected between time to reepithelialization and vascularization score at study entry, vascularization score at time of reepithelialization, and ulcer area at study entry in both groups. Time to reepithelialization was not correlated with age, sex, or duration of signs in either group. CONCLUSIONS AND CLINICAL RELEVANCE Topical application of undiluted heterologous serum was well tolerated by dogs with SCCEDs but, as an adjunct to standard treatment, did not reduce time to corneal reepithelialization.

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.

Corneal collagen cross-linking (CXL) for the treatment of melting keratitis in cats and dogs: a pilot study

OBJECTIVE

UV-A/riboflavin cross-linking (CXL) of corneal collagen fibers is an established, highly promising therapy for corneal melting in physician-based ophthalmology. A prospective pilot study was conducted to demonstrate proof of principle of this novel method for the treatment of melting corneal ulcers in dogs and cats.

PROCEDURES

After obtaining owner consent, CXL was performed in three cats and three dogs with corneal melting, which either affected the entire corneal surface or was resistant to conventional antibiotic and anticollagenolytic therapy, and affected parts or all of the corneal surface. Medical therapy was continued in all patients. The available follow-up ranged from 2 to 22.5 months and involved slit-lamp examination, fluorescein staining, and photographic documentation during all rechecks.

RESULTS

Surgical stabilization of the cornea was not necessary in any case, because progression of corneal melting was arrested in all cases within 1-20 days of CXL treatment. Corneal re-epithelization occurred within 7-40 days in all eyes. At 40 days after CXL, all eyes presented a quiescent corneal state without signs of active inflammation and with beginning scar formation. The complications observed in three of the six animals included a corneal sequestrum, superficial corneal stromal pigmentation, and bullous keratopathy.

CONCLUSIONS

This study shows the feasibility of CXL to treat progressive corneal melting in veterinary patients. CXL may represent a cost-efficient and safe alternative therapy in the treatment for corneal melting in veterinary ophthalmology. More investigations comparing the effectivity and complication rate of CXL to those of standard medical treatment are necessary.

Effects of oral treatment with N-acetylcysteine on the viscosity of intrauterine mucus and endometrial function in estrous mares

Persistent breeding-induced endometritis is ranked as the third most common medical problem in the adult mare and leads to enormous economic loss in horse breeding. In mares suffering from persistent breeding-induced endometritis, increased amounts of intrauterine (i.u.) fluid or viscous mucus in estrus or after breeding may act as a barrier for sperm and can contribute to low fertility. Current therapies of these mares aim to eliminate i.u. fluid and mucus by uterine lavage and/or administration of ecbolic drugs. Recently, i.u. administration of N-acetylcysteine (NAC) has been shown to support therapy in mares with endometritis. It was the objective of the present study to investigate effects of an oral administration of NAC on the viscosity of i.u. fluid in estrous mares. It was hypothesized that oral treatment with NAC reduces the viscosity of i.u. fluid and has a positive effect on the inflammatory response of the endometrium. Mares (n = 12) were included in the study as soon as estrus was detected (ovarian follicle >3.0 cm and endometrial edema), which was defined as Day 1. They were randomly assigned to a treatment (10 mg/kg NAC on Days 1-4) or a control group (no treatment). On days 1 and 5 i.u. mucus was collected and its rheologic properties were accessed. On Day 5, endometrial biopsies were obtained and evaluated for integrity of the luminal epithelium, number of polymorphonuclear neutrophils (PMN), staining for cyclooxygenase 2 (COX2), staining with Kiel 67 antigen (Ki-67), lectins and periodic acid Schiff (PAS). In the treatment group, viscosity of i.u. mucus increased significantly between Days 1 and 5 (P < 0.05), while no differences were found in control mares (n.s.). At no time were significant differences between treated and control mares seen. Integrity of epithelium was not affected. After NAC treatment the mean number of PMN in endometrial biopsies was significantly lower compared to mares of the control group (1.9 ± 0.3 vs. 4.8 ± 0.4; P < 0.05). Nuclear immunostaining for COX2 was significantly lower after NAC treatment compared to control mares (P < 0.05). Score for PAS and Alcain staining of mucus in deep uterine glands differed significantly between groups (both P < 0.05). We conclude that oral NAC treatment does not reduce viscosity of uterine mucus but has an antiinflammatory effect on the equine endometrium.

Optimal management of equine keratomycosis

Keratomycosis in the horse exists in several unique clinical forms. This paper discusses the diagnosis and clinical management of keratomycosis in the horse associated with tear film instability, epithelial keratopathy, subepithelial infiltrates, superficial and deep ulcers, plaques, melting ulcers, descemetoceles, iris prolapse, and stromal abscesses. Prompt diagnosis and aggressive treatment of equine keratomycosis can make a major difference in the maintenance of a cosmetic and visual eye.

A preliminary study of changes in tear film proteins in the feline eye following nictitating membrane removal

OBJECTIVE

To investigate the influence of nictitating membrane (third eyelid) removal on selected proteins in feline tears.

ANIMAL STUDIED

Domestic short-haired cats (7-17 months; 2.6-5.2 kg) were used.

PROCEDURES

Eye-flush tears were collected periodically for up to 18 weeks from both eyes of animals with nictitating membranes removed, but nictitating gland left intact, (n = 4) or with nictitating membranes intact (n = 4). Tear comparisons were based on total protein content (TPC) using micro bicinchoninic acid assay, immunoglobulin A (IgA), and matrix-metalloproteinase (MMP)-9 measurements using sandwich enzyme-linked immunosorbent assay (ELISA) and tear gelatinase activity using gelatin zymography. Expression of MMP-2 and -9 in nictitating membranes removed at baseline (week 0) and eyes collected at 18 weeks were also investigated in histological sections using immunoperoxidase for visualization.

RESULTS

Nictitating membrane removal did not significantly change TPC and MMP-9 in tears within the first 4 weeks. MMP-9 was not detected by ELISA in tears from eyes without nictitating membranes from week 5 onwards. IgA (%IgA of TPC) data varied between animals. Gelatin zymography showed increased MMP-2 and -9 activity in tears from eyes without nictitating membranes at week 1 and a decrease following week 2 post-surgery. MMP-2 and -9 were immunolocalised to conjunctival goblet cells of removed nictitating membranes and to the conjunctival epithelium, respectively. After 18 weeks, the distribution of MMPs in tissue was comparable between eyes with and without nictitating membranes.

CONCLUSIONS

Based on this preliminary study, nictitating membrane removal appeared to cause long-term changes in expression of tear proteins, including reduced MMP-9 expression.

Treatment of Corneal Ulcers: What are the Medical Options?

Practical relevance Corneal ulcers in cats (ulcerative keratitis) are a common presenting complaint, and are a frequent sequela to feline herpesvirus (FHV-1) infection. In fact, it is fair to assume an FHV-1 aetiology until proven otherwise. In practice, therefore, many cases of corneal ulceration can be treated medically, but treatment can frequently be challenging, with the need to tailor therapy carefully to the type of ulcer, the individual cat and its temperament.

Patient group All age groups and breeds can suffer with ulcerative keratitis although some breeds are over-represented for some types of corneal ulceration.

Evidence base The scientific literature on feline ulcerative keratitis is extensive, particularly that related to FHV-1 infection. This article reviews the medical treatment options for corneal ulceration in cats with reference to the current evidence base.

Proliferation of Streptococcus zooepidemicus and Pseudomonas aeruginosa within a simulated subpalpebral lavage flushed with equine serum

OBJECTIVE

To evaluate whether equine serum administered via a simulated subpalpebral lavage system (SPL) supports proliferation of Streptococcus zooepidemicus or Pseudomonas aeruginosa within the tubing.

PROCEDURES

A sterile i.v. catheter with injection cap was inserted into sterilized silicone tubing (Mila). To mimic an SPL within the dorsal conjunctival fornix, the tubing was secured to an elevated platform. The tip of the tubing extended from the platform into a vial containing culture medium just inoculated with approximately 1.5 x 10(8) CFU/mL P. aeruginosa or S. zooepidemicus. To mimic administration of medication, the tubing was infused twice daily with equine serum, sterile saline (negative control), or culture medium (positive control) followed by air. Incubation was at 25 or 37 degrees C. At 24, 48, and 72 h postinoculation, samples were obtained for bacterial culture from one simulated SPL for each experimental variant. The following sections were cultured: (i) tubing tip previously submerged in the inoculated culture medium, (ii) tubing mid-section, and (iii) tip of the i.v. catheter. The experiment was performed in triplicate.

RESULTS

Streptococcus zooepidemicus or P. aeruginosa were isolated from 100% of the tubing tips. Streptococcus zooepidemicus was isolated from one mid-section flushed with culture medium incubated at 37 degrees C. All other samples were negative for growth of the inoculated agents.

CONCLUSIONS

Streptococcus zooepidemicus and P. aeruginosa did not proliferate within silicone tubing infused with equine serum. These data suggest that topical serum can be safely administered through a superiorly placed SPL in clinical cases.

Kinetics of inhibition of purified bovine neutrophil matrix metalloproteinase 9 by low-molecular-weight inhibitors

OBJECTIVE

To measure the effects of lowmolecular-weight inhibitors on the activity of bovine neutrophil matrix metalloproteinase 9 (MMP-9).

SAMPLE POPULATION

Bovine MMP-9 purified from bovine neutrophilconditioned medium.

PROCEDURES

Neutrophils were degranulated by stimulation with phorbol ester. Enzyme purification was performed by use of gelatin affinity and gel-filtration chromatography. Activated enzyme was incubated with inhibitors prior to addition of substrate (gelatin fluorescein conjugate or fluorogenic peptide). Rates of enzymatic cleavage were determined by monitoring fluorescence as the reactions progressed. Values of IC(50) (molar concentration of compound that inhibits specific activity by 50%) and K(I) (in vitro inhibition constant) were determined.

RESULTS

Rates of enzymatic activity of monomeric and dimeric bovine MMP-9 measured by use of gelatin and peptide substrates were linear with respect to time and concentrations of enzyme and substrate. The MMP-9 was potently inhibited by hydroxamic acids (IC(50) for gelatin, 29.2 to 55.7 nM; IC(50) for peptide, 4.8 to 24.6 nM; K(I), 0.2 to 0.5 nM), whereas tetracyclines (IC(50) for gelatin, 30.1 to 112.7 MM; IC(50) for peptide, 48.0 to 123.8 MM; K(I), 25.2 to 61.4 microM) and chlorhexidine (IC(50) for gelatin, 139.1MM; IC(50) for peptide, 672.5MM to 1.7 mM; K(I), 495.0 to 663.0 MM) had limited inhibition. Gelatinase-specific inhibitor SB-3CT had intermediate potency (IC(50) for peptide, 185.0 to 290.0 nM; K(I), 66.5 to 86.0 nM).

CONCLUSIONS AND CLINICAL RELEVANCE

Bovine MMP-9 was potently inhibited by hydroxamic acids and gelatinase inhibitor. These compounds may be useful as modulators of neutrophil-mediated protease activity in cattle.

Doxycycline levels in preocular tear film of horses following oral administration

OBJECTIVE

To determine the concentration of doxycycline in preocular tear film following oral administration in horses as a possible therapeutic modality for infectious and keratomalacic equine keratitis.

PROCEDURE

Eight broodmares without ocular disease from a Thoroughbred breeding facility were included in this study. Each mare received 20 mg/kg of doxycycline by mouth once daily in the morning for five consecutive days. Tears were collected 1 h after doxycycline administration starting on day one of administration and continuing for 10 consecutive days. Doxycycline levels in the tears were measured using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS).

RESULTS

Doxycycline was present in the tears of each mare at low microg/mL levels with the highest concentration appearing on the third to fifth days (8.21-9.83 microg/mL). Doxycycline levels had fallen below quantifiable ranges by day 10. No systemic side-effects were noted in any of the horses included in this study.

CONCLUSIONS

Oral doxycycline is present in preocular tear film of normal horses with noninflamed eyes and may be useful as treatment in equine ulcerative keratomalacia. The oral dose listed was tolerated well by the horses in this study. The drug levels attained at 20 mg/kg once daily orally of doxycycline may aid in the treatment of corneal ulceration in horses, but further study is warranted.

Spontaneous chronic corneal epithelial defects in dogs: a review

Spontaneous chronic corneal epithelial defects (SCCEDs) in dogs are typically found in middle-aged dogs of all breeds. These epithelial defects may be present for weeks to months, particularly if left untreated or if treated inappropriately. Typical histopathological findings include loss of the corneal epithelial basement membrane and formation of a superficial, acellular, hyalinized zone in the stroma. Together, these histological abnormalities lead to delayed wound healing and poor epithelial adhesion. Epithelial debridement, anterior stromal puncture, grid keratotomy, and superficial keratectomy are the most common treatment options applied to the defects. Procedures that address the stromal changes present generally have a higher success rate than epithelial debridement alone.

Proteinases of the cornea and preocular tear film

Maintenance and repair of corneal stromal extracellular matrix (ECM) requires a tightly coordinated balance of ECM synthesis, degradation and remodeling in which proteolytic enzymes (proteinases) perform important functions. There are natural proteinase inhibitors present in preocular tear film (PTF) and cornea simultaneously with proteinases that prevent excessive degradation of normal healthy tissue. Disorders occur when there is an imbalance between proteinases and proteinase inhibitors in favor of the proteinases, causing pathologic degradation of stromal collagen and proteoglycans in the cornea. Two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, are of major importance in terms of remodeling and degradation of the corneal stromal collagen. Immunohistochemical studies have shown different origins of MMP-2 and -9. MMP-2 is synthesized by corneal keratocytes and performs a surveillance function in the normal cornea, becoming locally activated to degrade collagen molecules that occasionally become damaged. Alternatively, MMP-9 may be produced by epithelial cells and polymorphonuclear neutrophils following corneal wounding. Because the cornea is in close contact with the preocular tear film (PTF), proteinases have been evaluated in the PTF. In damaged corneas, total proteolytic activity in the tear fluid was found to be significantly increased compared to normal eyes and contralateral eyes. Studies analyzing the proteolytic activity in serial PTF samples during corneal healing led to the following conclusions: ulcerative keratitis in animals is associated with initially high levels of tear film proteolytic activity, which decrease as ulcers heal; proteinase levels in melting ulcers remain elevated leading to rapid progression of the ulcers. The success of medical and surgical treatment of the corneal ulcers is reflected by the proteolytic activity in tears. In animals, successful treatment leads to a rapid reduction in tear film proteolytic activity that corresponds with the improvement in the clinical signs of corneal ulceration. The in vitro effects of various compounds on proteolytic activity in the tear fluid of animals with ulcerative keratitis have been evaluated and their important inhibitory effects have been confirmed. Because these various compounds utilize different mechanisms to inhibit various families of proteinases, a combination of these proteinase inhibitors may be beneficial.

Matrix metalloproteinase mRNA expression in canine anal furunculosis lesions

Although the aetiology of anal furunculosis (AF) in dogs is poorly understood, there is evidence for an underlying immune dysfunction. This is illustrated by the presence of a T helper type 1 cytokine mRNA profile in AF lesions and the clinical response to ciclosporin therapy. Expression of MMPs 2, 9 and 13 were evaluated in AF lesional biopsies by real-time quantitative RT-PCR. There was significantly increased expression of both MMP-9 and MMP-13 mRNA in AF biopsies compared to controls (p<0.001) but no significant difference in MMP-2 mRNA expression. Since MMP-9 and MMP-13 are primarily produced by macrophages, these data suggest that ulceration could be the result of aberrant activation of this cell type in the tissues. It is feasible that such pathological macrophage activity occurs in response to interferon-gamma secreted by T helper type 1 cells. This could explain why the lesions resolve following treatment with the immunosuppressive drug ciclosporin.

Infections of the Head and Ocular Structures in the Horse

Infectious conditions of the equine head are commonly encountered in clinical practice. Pathogenic bacterial, viral, and fungal organisms may localize in the extensive nasal passages, paranasal sinuses, and guttural pouches, creating a range of clinical signs and conditions that can be severe enough to lead to unexpected fatality. Renewed interest in equine dentistry has led to a greater recognition of dental disease that is associated with infection. This article focuses on bacterial and fungal infections of the main anatomic regions of the equine head, where advances in diagnosis and management have been made or consolidated in recent years. It also addresses recent advances made in the area of infectious equine corneal disease, including bacterial, viral, and fungal etiologies. Recent developments in equine recurrent uveitis as it relates to infectious diseases and ocular manifestations of systemic disease are also discussed.