Assessment of Topical Therapies for Improving the Optical Clarity Following Stromal Wounding in a Novel Ex Vivo Canine Cornea Model

Pirfenidone: A Promising Drug in Ocular Therapeutics

Pirfenidone, initially indicated for lung fibrosis, has gone beyond its original purpose, and shown promise in eye care. This detailed review tracks its evolution from lung treatment to aiding eye healing as evidenced by published literature. Pirfenidone's multifaceted attributes extend to mitigating corneal fibrosis, inflammation, and trauma. Through rigorous investigations, its efficacy emerges in diabetic retinopathy, macular degeneration, and postoperative glaucoma interventions. As an unheralded protagonist, pirfenidone reshapes ocular care paradigms, inviting renewed research opportunities.

Antifibrotic Effects of Caffeine, Curcumin and Pirfenidone in Primary Human Keratocytes

We evaluated the small molecules (AFM) caffeine, curcumin and pirfenidone to find non-toxic concentrations reducing the transformation of activated human corneal stromal keratocytes (aCSK) to scar-inducing myofibroblasts (MYO-SF). CSK were isolated from 16 human corneas unsuitable for transplantation and expanded for three passages in control medium (0.5% FBS). Then, aCSK were exposed to concentrations of caffeine of 0−500 μM, curcumin of 0−200 μM, pirfenidone of 0−2.2 nM and the profibrotic cytokine TGF-β1 (10 ng/mL) for 48 h. Alterations in viability and gene expression were evaluated by cell viability staining (FDA/PI), real-time polymerase chain reaction (RT-PCR) and immunocytochemistry. We found that all AFMs reduced cell counts at high concentrations. The highest concentrations with no toxic effect were 100 µM of caffeine, 20 µM of curcumin and 1.1 nM of pirfenidone. The addition of TGF-β1 to the control medium effectively transformed aCSK into myofibroblasts (MYO-SF), indicated by a 10-fold increase in α-smooth muscle actin (SMA) expression, a 39% decrease in lumican (LUM) expression and a 98% decrease in ALDH3A1 expression (p < 0.001). The concentrations of 100 µM of caffeine, 20/50 µM of curcumin and 1.1 nM of pirfenidone each significantly reduced SMA expression under TGF-β1 stimulation (p ≤ 0.024). LUM and ALDH3A1 expression remained low under TGF-β1 stimulation, independently of AFM supplementation. Immunocytochemistry showed that 100 µM of caffeine, 20 µM of curcumin and 1.1 nM of pirfenidone reduce the conversion rate of aCSK to SMA+ MYO-SF. In conclusion, in aCSK, 100 µM of caffeine, 20 µM of curcumin and 1.1 nM of pirfenidone significantly reduced SMA expression and MYO-SF conversion under TGF-β1 stimulation, with no influence on cell counts. However, the AFMs were unable to protect aCSK from characteristic marker loss.

Evaluation of a novel combination of TRAM-34 and ascorbic acid for the treatment of corneal fibrosis in vivo

Corneal injury and aberrant wound healing commonly result in corneal fibrosis and subsequent vision loss. Intermediate-conductance calmodulin/calcium-activated K+ channels (KCa3.1) have been shown to promote fibrosis in non-ocular and ocular tissues via upregulation of transforming growth factor beta (TGFβ). TRAM-34 is a selective inhibitor of KCa3.1 and reduces fibrosis by downregulation of TGFβ-induced transdifferentiation of stromal fibroblasts to myofibroblasts. Ascorbic acid has been demonstrated to be effective in promoting corneal re-epithelialization and reduction of neovascularization via anti-VEGF and anti-MMP mechanisms. This study evaluates tolerability and efficacy of a novel combination of TRAM-34 (25μM) and ascorbic acid (10%) topical treatment for corneal fibrosis using an established in vivo rabbit model and conducting clinical eye examinations. Markers of corneal fibrosis were evaluated in all corneas at study endpoint via histopathology, immunofluorescence, and quantitative real-time PCR. The eyedrop treated eyes showed significantly improved clinical outcomes based on modified McDonald Shadduck scores, reduction of clinical haze on Fantes scores, and reduction of central corneal thickness (CCT). At cellular and molecular levels, eyedrop treatment also significantly reduced expression of alpha smooth muscle actin (α-SMA) mRNA and protein, collagen III mRNA, and fibronectin mRNA compared to non-treated eyes. Our study suggests that a tested new bimodal eyedrop is well tolerated and effectively reduces corneal fibrosis/haze in rabbits in vivo.

Therapeutic effects of equine amniotic membrane suspension on corneal re-epithelialization and haze in a modified lagomorph ex vivo wound healing model

OBJECTIVE

To investigate the therapeutic effects of topical equine amniotic membrane (eAM) suspension following corneal wounding in a controlled experimental setting.

PROCEDURES

Equine amniotic membrane was collected, gamma irradiated, homogenized for topical suspension preparation, and cryopreserved. Corneoscleral rims harvested from fresh rabbit globes were wounded via keratectomy and were maintained in an air-liquid interface ex vivo corneal culture model. Treatment groups included topical gamma irradiated eAM suspension (n = 20) and a control group (n = 20). Re-epithelialization of the wound was assessed with daily photographic evaluation of area of fluorescein uptake (mm² ). Corneal wound haze after a 21-day period was assessed by photographic analysis of haze area (mm² ) and pixel intensity (0-255). Histologic processing of corneal tissue was performed, and protein identification of eAM suspension using Liquid chromatography-mass spectrometry (LC-MS).

RESULTS

The average day of complete corneal re-epithelialization in controls (5.5 ± 1.1) and topically treated (5.5 ± 0.6) corneas, and rates of reduction in area of fluorescein uptake over time did not significantly differ (p = .44). The corneal wound haze was significantly reduced in mean area by approximately 52% and intensity by 57% in corneas treated with topical eAM suspension (p < .05), compared to controls 21 days following wounding. Protein analysis identified numerous proteins, specifically decorin, dermatopontin, and lumican, which have previously been documented in eAM.

CONCLUSIONS

Area and intensity of corneal wound haze were significantly reduced in corneas treated with gamma irradiated eAM suspension, which may be due to previously identified therapeutic proteins which promote corneal clarity.

Assessment of Cidofovir for Treatment of Ocular Bovine Herpesvirus-1 Infection in Cattle Using an Ex-Vivo Model

Bovine herpesvirus-1 (BoHV-1) infection contributes to keratoconjunctivitis, respiratory disease, and reproductive losses in cattle. The objective of this study was to determine the most appropriate ophthalmic antiviral agent for BoHV-1 inhibition using in-vitro culture and novel ex-vivo bovine corneal modeling. Half-maximal inhibitory concentrations of BoHV-1 were determined for cidofovir, ganciclovir, idoxuridine, and trifluridine via in-vitro plaque reduction assays. In-vitro cytotoxicity was compared amongst these compounds via luciferase assays. Trifluridine and cidofovir were the most potent BoHV-1 inhibitors in vitro, while trifluridine and idoxuridine were the most cytotoxic agents. Therefore, cidofovir was the most potent non-cytotoxic agent and was employed in the ex-vivo corneal assay. Corneoscleral rings (n = 36) from fresh cadaver bovine globes were harvested and equally divided into an uninfected, untreated control group; a BoHV-1-infected, untreated group; and a BoHV-1-infected, cidofovir-treated group. Virus isolation for BoHV-1 titers was performed from corneal tissue and liquid media. Histologic measurements of corneal thickness, epithelial cell density, and tissue organization were compared between groups. Substantial BoHV-1 replication was observed in infected, untreated corneas, but BoHV-1 titer was significantly reduced in cidofovir-treated (1.69 ± 0.08 × 10³ PFU/mL) versus untreated (8.25 ± 0.25 × 10⁵ PFU/mL, p < 0.0001) tissues by day 2 of culture. No significant differences in histologic criteria were observed between groups. In conclusion, cidofovir warrants further investigation as treatment for BoHV-1 keratoconjunctivitis, with future studies needed to assess in-vivo tolerability and efficacy.

Interleukin-6 and lactate dehydrogenase expression in a novel ex vivo rocking model of equine corneal epithelial wound healing

PURPOSE

To establish a physiologically relevant ex vivo model of equine corneal epithelial wound healing.

METHODS

Fourteen equine corneas were randomly assigned to one of two groups: wounded (n = 8) or unwounded (n = 6) controls. In the wounded group, the axial corneal epithelium was removed by applying a 6 mm filter paper disk soaked in 1N-NaOH for 60 s. Corneas were subsequently cultured using an air-liquid interface model. Evaluation of corneal healing was performed daily, and culture medium was collected. Corneas were randomly assigned to undergo processing via histopathology and RNAscope in situ hybridization for interleukin-6 (IL-6) and alpha-smooth muscle actin (αSMA) expression at T24, T48, and T72 h after wounding. Media of the cultured corneas were evaluated for the presence of lactate dehydrogenase (LDH) by a colorimetric assay.

RESULTS

The ulcerated area of the wounded corneas decreased over time and all corneas healed within 72 h. Histologically, normal corneal architecture was observed including healthy epithelium (in areas other than the ulcerated ones), minimal stromal edema, intact endothelium, and Descemet's membrane. IL-6 expression was increased in wounded corneas compared with unwounded controls. LDH expression was elevated for both wounded and unwounded corneas at T24 but decreased substantially and was not detected at T48 in media from wounded and unwounded corneas, respectively. No αSMA expression was detected from either wounded or unwounded corneas.

CONCLUSIONS

The equine air-liquid interface, ex vivo, corneal epithelial wound healing model is effective and physiologically relevant. This model can be used in future studies evaluating various corneal therapies.

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.

Dexmedetomidine and Tear Production: Evaluation in Dogs as Spontaneous Model for Ocular Surface Disorders

Simple Summary

The general anesthesia or sedation reduces both the tear production and the stability of tear film that protect corneal surface, predisposing itself to the exposure keratopathy. The aim of the present study was to evaluate the effects of intramuscular dexmedetomidine (DEX) on canine tear production, measured by standardized Schirmer Tear Test 1 (STT-1) strips, for the 8 h following sedation, in dogs. A significant effect of time on canine tear production was found, highlighting that dexmedetomidine sedative protocol significantly affects tear production in dogs. It is recommended to treat the canine eyes with tear substitutes to protect ocular surface health and the welfare of the dogs. The ocular lubrication should be performed during and up to 12 h after sedation. The present report could provide preliminary information to better understand the effect of DEX on the tear film dynamics.

Abstract

Tear film provides lubrication and protection to the ocular surface. The sedation reduces tear production, often leading to perioperative exposure keratopathy. The aim of the present study was to report the effects of intramuscular dexmedetomidine on canine tear production, measured by STT-1, for an experimental period of 8 h after sedation. Ten dogs who underwent sedation for routine radiologic assessment were recruited for the study. In all animals, tear production in right and left eyes was measured 15 min before sedation (T0: basal values) and 20 min (T20), 1 h (T1), 2 h (T2), 4 h (T4) and 8 h (T8) after drug administration. Analysis of variance and post hoc Bonferroni test (p < 0.05) were performed. A significant effect of time on canine tear production was found. The tear production returned to basal values at T8. So, it is recommended to treat the canine eyes with tear substitutes during and up to 12 h after sedation.

Electrolyte composition of tears in normal dogs and its comparison to serum and plasma

PURPOSE

The dog is an important animal model for tear dysfunction diseases, however to-date the electrolyte composition of the dog's tears is unknown. The aim of this study was to analyze the electrolyte content of canine tears and compare it to serum and plasma.

METHODS

Tear samples were collected from 18 eyes of 9 dogs. Blood for serum was collected in tubes with no anticoagulants; plasma was obtained by using two different anticoagulants: Citrate-Phosphate-Dextrose (CPD) and heparin. The electrolytes were measured in all samples, analyzed, and compared.

RESULTS

Most of the electrolyte values in tears were statistically different (P < 0.05) from electrolyte values in serum and plasma. Potassium and chloride values were significantly higher in tears compared to serum and plasma, while calcium and phosphate values were significantly lower. Sodium values in tears were higher than in serum and heparinized-plasma, but lower than CPD-plasma. Bicarbonate values were lower in tears compared to serum and heparinized plasma, but was not statistically different than CPD-plasma. While magnesium values were lower in tears compared to serum and heparinized-plasma, the difference was not statistically different.

CONCLUSIONS

Herein, we report for the first time the electrolyte composition of the canine tears and its comparison to serum and plasma.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).

Ophthalmic examination, biometry, and histologic findings in captive inland bearded dragons (Pogona vitticeps)

OBJECTIVE

To report ophthalmic examination, biometry, phenol red thread test (PRTT), intraocular pressure (IOP), and histologic findings from a private collection of inland bearded dragons (Pogona vitticeps).

ANIMALS STUDIED

Fourteen inland bearded dragons.

PROCEDURES

Complete ophthalmic examinations were performed on all animals, including slit-lamp biomicroscopy, indirect ophthalmoscopy, fluorescein stain, phenol red thread test, and rebound tonometry. B-mode ultrasonography was used to measure anterior chamber depth, axial lens thickness, vitreal chamber depth, and axial globe length. Horizontal corneal diameter was estimated using ImageJ software. Histologic assessment was obtained for one of the bearded dragons that died following the study period.

RESULTS

The median PRTT value was 7.27 mm/15 seconds. Mean IOP was 6.29 ± 1.60 mm Hg and 2.14 ± 1.37 mm Hg using the dog and undefined calibration settings, respectively. Median axial globe length was 11.75 mm. Mean anterior chamber depth and mean lens thickness were 2.06 ± 0.35 mm and 3.38 ± 0.45 mm, respectively. Median vitreal chamber depth was 6.79 mm. Mean horizontal corneal diameter was 5.138 ± 0.346 mm. Two distinct ocular phenotypes were observed, with two of the bearded dragons having corneal globosa, deep anterior chambers, and tufts of iridal vessels and fibrillar material extending into the anterior chamber.

CONCLUSIONS

The ultrasound biometry, PRTT, and rebound tonometry results may serve as a guideline for ophthalmic parameters in healthy bearded dragons. Examination and testing of greater numbers of animals are necessary to establish true reference ranges and determine if the observed ocular phenotypes represent normal variants or pathologic changes.

Development and assessment of a novel ex vivo corneal culture technique involving an agarose-based dome scaffold for use as a model of in vivo corneal wound healing in dogs and rabbits

OBJECTIVE

To develop and assess a novel ex vivo corneal culture technique involving an agarose-based dome scaffold (ABDS) for use as a model of in vivo corneal wound healing in dogs and rabbits.

SAMPLE

Corneas from clinically normal dogs (paired corneas from 8 dogs and 8 single corneas) and rabbits (21 single corneas).

PROCEDURES

8 single dog corneas (DCs), 1 DC from each pair, and 10 rabbit corneas (RCs) were wounded with an excimer laser; 1 DC from each pair and 11 RCs remained unwounded. Corneas were cultured for 21 days on ABDSs (8 pairs of DCs and all RCs) or on flat-topped scaffolds (8 single DCs). The surface area of corneal fluorescein retention was measured every 6 (DCs) or 12 (RCs) hours until full corneal epithelialization was detected. Changes in corneal clarity were evaluated at 0, 7, 14, and 21 days.

RESULTS

Median time to full epithelialization for wounded dog and rabbit corneas was 48 and 60 hours, respectively; among wounded DCs, time to full epithelization did not differ by scaffold type. After 21 days of culture on ABDSs, all DCs and RCs that epithelialized developed a circular, diffuse, cloud-like pattern of optical haze, whereas DCs cultured on flat-topped scaffolds developed a focal, crater-like region of optical haze. All corneas on the ABDSs maintained convex curvature throughout the study.

CONCLUSIONS AND CLINICAL RELEVANCE

Wounded ex vivo DCs and RCs cultured on ABDSs reliably epithelialized, formed optical haze (consistent with in vivo wound healing), and maintained convex curvature. This culture technique may be adaptable to other species.

An ex vivo cornea infection model

In vitro screening and testing of drugs and devices is necessary, but in vitro conditions differ greatly from those found in vivo. These differences can lead to false promises of efficacy, or can hide problems of tissue compatibility. Models with ex vivo tissues can be highly valuable bridges which provide relevant matrices for testing [1], [2], [3], [4], [5], [6], [7], [8], [9]. Ex vivo tissue models which are closer both biochemically and biophysically can provide useful feedback in a more time- and cost-efficient manner. Herein we describe an ex vivo corneal model for use in drug delivery testing and corneal infection modeling [10]. The protocol covers the tissue harvesting, sterilization, inoculation, and bacterial load quantification. We envision that the model can be used to study bacterial physiology on metabolizable matrices and to study the direct effects of microbial colonization on the cornea's integrity and clarity.•

Devitalized cornea.

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Non-submersed conditions.

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Contact lens compatible.