Molecular Mechanisms of Suberoylanilide Hydroxamic Acid in the Inhibition of TGF-β1-Mediated Canine Corneal Fibrosis

Objective—To investigate molecular mechanisms mediating anti-fibrotic effect of SAHA in the canine cornea using an in vitro model. We hypothesized that SAHA attenuates corneal fibrosis by modulating Smad-dependent and, to a lesser extent, Smad-independent signaling pathways activated by TGF-β1, as well as matrix metalloproteinase (MMP) activity. Methods—Cultured canine corneal fibroblasts (CCF) were incubated in the presence/absence of TGF-β1 (5ng/ml) and SAHA (2.5μM) for 24hrs. Western blot analysis was used to quantify non-phosphorylated and phosphorylated isoforms of Smad2/3, p38 MAP kinase (MAPK), ERK1/2 and JNK1. Real-time PCR and zymography were utilized to quantify MMP1, MMP2, MMP8 and MMP9 mRNA expression and MMP2 and MMP9 protein activity, respectively. Results—TGF-β1 treatment caused a significant increase in phospho-Smad2/3 and phospho-p38 MAPK. SAHA treatment reduced TGF-β1-induced phosphorylation of Smad2/3 but not of p38 MAPK. TGF-β1 did not modulate the phosphorylation of ERK1/2 or JNK1. SAHA caused a significant reduction in phospho-ERK1/2 expression regardless of concurrent TGF-β1 treatment. Neither SAHA alone nor in combination with TGF-β1 altered phospho-JNK1 expression. TGF-β1 significantly increased MMP1 and MMP9 mRNA expression but did not alter MMP2 mRNA. SAHA treatment attenuated TGF-β1-induced MMP9 mRNA expression while significantly enhancing TGF-β1-induced MMP1 mRNA expression. Zymography detected reduced expression of MMP2 and MMP9 proteins in untreated control CCF. TGF-β1 treatment did not alter their expression but SAHA treatment +/−TGF-β1 significantly increased MMP2 and MMP9 protein expression. Conclusions—The corneal anti-fibrotic effects of SAHA involve multiple mechanisms including modulation of canonical and non-canonical components of TGF-β1 intracellular signaling and MMP activity

Isolation and Cultivation of Equine Corneal Keratocytes, Fibroblasts and Myofibroblasts

Objective—To establish an in vitro model for the investigation of equine corneal wound healing. To accomplish this goal, a protocol to isolate and culture equine corneal keratocytes, fibroblasts and myofibroblasts was developed. Animal material—Equine corneal buttons were aseptically harvested from healthy research horses undergoing humane euthanasia for reasons unrelated to this study. Slit-lamp biomicroscopy was performed prior to euthanasia by a board-certified veterinary ophthalmologist to ensure that all samples were harvested from horses free of anterior segment disease. Procedure—Equine corneal stroma was isolated using mechanical techniques and stromal subsections were then cultured. Customized media at different culture conditions was used to promote growth and differentiation of corneal stromal cells into keratocytes, fibroblasts and myofibroblasts. Results—Cell culture techniques were successfully used to establish a method for the isolation and culture of equine corneal keratocytes, fibroblasts and myofibroblasts. Immunohistochemical staining for alpha-smooth muscle and F-actin was used to definitively differentiate the three cell types. Conclusion—Equine corneal stromal keratocytes, fibroblasts and myofibroblasts can be predictably isolated and cultured in vitro using this protocol

Efficacy and Safety of Mitomycin C as an Agent to Treat Corneal Scarring in Horses Using an \u3cem\u3ein vitro\u3c/em\u3e Model

Objective—Mitomycin C (MMC) is used clinically to treat corneal scarring in human patients. We investigated the safety and efficacy of MMC to treat corneal scarring in horses by examining its effects at the early and late stages of disease using an in-vitro model. Procedure—An in-vitro model of equine corneal fibroblast (ECF) developed was used. The equine corneal fibroblast or myofibroblast cultures were produced by growing primary ECF in the presence or absence of transforming growth factor beta-1 (TGFβ1) under serum-free conditions. The MMC dose for the equine cornea was defined with dose-dependent trypan blue exclusion and MTT [(3-4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays after applying MMC to the cultures once for 2 minutes. The efficacy of MMC to control corneal scarring in horses was determined by measuring mRNA and protein expression of corneal scarring markers (α-smooth muscle actin and F-actin) with western blotting, immunocytochemistry and/or quantitative realtime polymerase chain reactions. Results—A single 2 minutes treatment of 0.02% or less MMC did not alter ECF phenotype, viability, or cellular proliferation whereas 0.05% or higher MMC doses showed mild-to-moderate cellular toxicity. The TGFβ1 at 1ng/ml showed significant myofibroblast formation in ECF under serum-free conditions. A single 2 minute, 0.02% MMC treatment 24 hours (early) after TGFβ1 stimulation significantly reduced conversion of ECF to myofibroblasts, however, a single 0.02% MMC treatment 11 days after TGFβ1 stimulation showed moderate myofibroblast inhibition. Conclusions—That MMC safely and effectively reduced scarring in ECF by reducing the degree of transdifferentiation of corneal fibroblasts to myofibroblasts in vitro. Further clinical invivo investigations are warranted using MMC in horses

Gene Delivery in the Equine Cornea: A Novel Therapeutic Strategy

Objective—To determine if hybrid adeno-associated virus serotype 2/5 (AAV5) vector can effectively deliver foreign genes into the equine cornea without causing adverse side effects. The aims of this study were to: (i) evaluate efficacy of AAV5 to deliver therapeutic genes into equine corneal fibroblasts (ECFs) using enhanced green fluorescent protein (EGFP) marker gene and (ii) establish the safety of AAV5 vector for equine corneal gene therapy. Animal Material—Primary ECF cultures were harvested from healthy donor equine corneas. Cultures were maintained at 370C in humidified atmosphere with 5% CO2. Procedure—AAV5 vector expressing EGFP under control of hybrid cytomegalovirus (CMV) + chicken β-actin (CBA) promoter was applied topically to ECF. Expression of delivered EGFP gene in ECF was quantified using fluorescent microscopy. Using DAPI staining, the total number of cells and transduction efficiency of tested AAV vector was determined. Phase contrast microscopy, trypan blue and TUNEL assays were used to determine toxicity and safety of AAV5 for ECFs. Results—Topical AAV5 application successfully transduced significant numbers of ECFs. Transduction efficiency was 13.1%. Tested AAV5 vector did not cause phenotype change or significant cell death and cell viability was maintained. Conclusions—Tested AAV5 vector is effective and safe for gene therapy in ECFs in vitro. Clinical Relevance—Tested AAV5 vector has potential to extend a novel gene therapy approach to treat equine corneal disease in vivo

Development of a Novel \u3cem\u3eEx Vivo\u3c/em\u3e Equine Corneal Model

Objective To develop an ex vivo equine corneal organ culture model. Specifically, to assess the equine cornea\u27s extracellular matrix and cellularity after 7 days using two different culture techniques: either (i) immersion system or (ii) air/liquid interface system, to determine the best ex vivo equine corneal model. Animals Studied Fourteen healthy equine corneas of various breeds. Procedures Equine corneas with 2 mm of perilimbal sclera were freshly harvested from 7 horses undergoing humane euthanasia. One corneal–scleral ring (CSR) from each horse was randomly placed in the (i) immersion condition organ culture system (IC), with the contralateral CSR being placed in the (ii) air/liquid interface organ culture system (ALC) for 7 days. All corneas were evaluated using serial daily gross photography, histology, qPCR, and TUNEL assay. Results corneal–scleral rings placed in the IC (i) had complete loss of corneal transparency on gross photography by 7 days, showed a significant level of corneal stromal disorganization, significantly increased α‐SMA levels on qPCR, and apoptosis on TUNEL assay compared to controls. The ALC (ii) had weak stromal disorganization on histopathologic examination and was not significantly different from normal equine corneal controls on all other evaluated parameters. Conclusions The air–liquid interface organ culture system maintains the equine cornea\u27s extracellular matrix and preserves corneal transparency, while the immersion condition results in near complete degradation of normal equine corneal architecture after 7 days in culture. The air–liquid organ culture is a viable option to maintain a healthy equine cornea in an ex vivo setting for wound healing studies

Targeted AAV5-Smad7 Gene Therapy Inhibits Corneal Scarring \u3cem\u3ein vivo\u3c/em\u3e

Corneal scarring is due to aberrant activity of the transforming growth factor β (TGFβ) signaling pathway following traumatic, mechanical, infectious, or surgical injury. Altered TGFβ signaling cascade leads to downstream Smad (Suppressor of mothers against decapentaplegic) protein-mediated signaling events that regulate expression of extracellular matrix and myogenic proteins. These events lead to transdifferentiation of keratocytes into myofibroblasts through fibroblasts and often results in permanent corneal scarring. Hence, therapeutic targets that reduce transdifferentiation of fibroblasts into myofibroblasts may provide a clinically relevant approach to treat corneal fibrosis and improve long-term visual outcomes. Smad7 protein regulates the functional effects of TGFβ signaling during corneal wound healing. We tested that targeted delivery of Smad7 using recombinant adeno-associated virus serotype 5 (AAV5-Smad7) delivered to the corneal stroma can inhibit corneal haze post photorefractive keratectomy (PRK) in vivo in a rabbit corneal injury model. We demonstrate that a single topical application of AAV5-Smad7 in rabbit cornea post-PRK led to a significant decrease in corneal haze and corneal fibrosis. Further, histopathology revealed lack of immune cell infiltration following AAV5-Smad7 gene transfer into the corneal stroma. Our data demonstrates that AAV5-Smad7 gene therapy is relatively safe with significant potential for the treatment of corneal disease currently resulting in fibrosis and impaired vision

Development of a Novel \u3cem\u3ein vivo\u3c/em\u3e Corneal Fibrosis Model in the Dog

The aim of this study was to develop a novel in vivo corneal model of fibrosis in dogs utilizing alkali burn and determine the ability of suberanilohydroxamic acid (SAHA) to inhibit corneal fibrosis using this large animal model. To accomplish this, we used seven research Beagle dogs. An axial corneal alkali burn in dogs was created using 1 N NaOH topically. Six dogs were randomly and equally assigned into 2 groups: A) vehicle (DMSO, 2 μL/mL); B) anti-fibrotic treatment (50 μM SAHA). The degree of corneal opacity, ocular health, and anti-fibrotic effects of SAHA were determined utilizing the Fantes grading scale, modified McDonald-Shadduck (mMS) scoring system, optical coherence tomography (OCT), corneal histopathology, immunohistochemistry (IHC), and transmission electron microscopy (TEM). The used alkali burn dose to produce corneal fibrosis was well tolerated as no significant difference in mMS scores between control and treatment groups (p=0.89) were detected. The corneas of alkali burned dogs showed significantly greater levels of α-smooth muscle actin, the fibrotic marker, than the controls (p=0.018). Total corneal thickness of all dogs post-burn was significantly greater than baseline OCT images irrespective of treatment (p=0.004); TEM showed that alkali burned corneas had significantly greater minimum and maximum interfibrillar distances than the controls (p=0.026, p=0.018). The tested topical corneal alkali burn dose generated significant opacity and fibrosis in dog corneas without damaging the limbus as evidenced by histopathology, IHC, TEM, and OCT findings, and represents a viable large animal corneal fibrosis in vivo model. Additional in vivo SAHA dosing studies with larger sample size are warranted

Retinal oxygenation and oxygen metabolism in Abyssinian cats with a hereditary retinal degeneration

PURPOSE. To investigate the effects of a hereditary retinal degeneration on retinal oxygenation and determine whether it is responsible for the severe attenuation of retinal circulation in hereditary photoreceptor degenerations. METHODS. Seven adult Abyssinian cats affected by hereditary retinal degeneration were studied. Oxygen microelectrodes were used to collect spatial profiles of retinal oxygenation in anesthetized animals. A one-dimensional model of oxygen diffusion was fitted to the data to quantify photoreceptor oxygen utilization (QO 2 ). RESULTS. Photoreceptor QO 2 progressively decreased until it reached zero in the end stage of the disease. Average inner retinal oxygen tension remained within normal limits at all disease stages, despite the observed progressive retinal vessel attenuation. Light affected photoreceptors normally, decreasing QO 2 by ϳ50% at all stages of the disease. CONCLUSIONS. Loss of photoreceptor metabolism allows choroidal oxygen to reach the inner retina, attenuating the retinal circulation in this animal model of retinitis pigmentosa (RP) and probably also in human RP. As the degeneration progresses, there is a strong relationship between changes in the a-wave of the ERG and changes in rod oxidative metabolism, indicating that these two functional measures change together. 2-6 We hypothesized that the pronounced vasoconstriction results from decreased oxygen utilization by the outer retina after photoreceptor loss. Because less choroidal oxygen is used by the photoreceptors, it should reach the inner retina, where oxygen is known to cause constriction of retinal vessels. 10 Vessels do not simply constrict. Eventually they are lost in animals with photoreceptor degenerations. 6 These studies suggest not only a physiological role of oxygen, but a trophic (or antitrophic) one as well. In the present study, we further examined the hypothesis that oxygen from the choroid is responsible for attenuation of the retinal circulation, by characterizing changes in retinal oxygenation and oxidative metabolism during the progression of a feline hereditary retinal degeneration in a colony of Abyssinian cats. 3 The autosomal recessive genetic defect in this animal is not yet known, but it exhibits a slow rod-cone degeneration similar to human RP. Using measurements of intraretinal oxygen tension (PO 2 ) in these animals and our mathematical model of oxygen diffusion and utilization, 13 A preliminary report of these results has been presented (Linsenmeier RA, et al. IOVS 2000;41:ARVO Abstract 4721). METHODS Animals Eight Abyssinian cats affected by a hereditary retinal degeneration were studied. These are the same cats in which an ERG study, reported in this issue, was also performed. 13 3,13 The hematocrit from one stage 3 animal was low because of surgical complications and continued to decrease during the experiment. In this animal, the earlier choroidal PO 2 and the inner retinal PO 2 , which were in the normal range, are included in the reported data, but oxygen consumption data and later choroidal PO 2 data from this animal were not used. Electrode problems prevented data collection in one stage 2 animal. Data from animals with retinal degeneration were compared to similar data obtained from normal cats

Targeted AAV5-Smad7 gene therapy inhibits corneal scarring in vivo.

Corneal scarring is due to aberrant activity of the transforming growth factor β (TGFβ) signaling pathway following traumatic, mechanical, infectious, or surgical injury. Altered TGFβ signaling cascade leads to downstream Smad (Suppressor of mothers against decapentaplegic) protein-mediated signaling events that regulate expression of extracellular matrix and myogenic proteins. These events lead to transdifferentiation of keratocytes into myofibroblasts through fibroblasts and often results in permanent corneal scarring. Hence, therapeutic targets that reduce transdifferentiation of fibroblasts into myofibroblasts may provide a clinically relevant approach to treat corneal fibrosis and improve long-term visual outcomes. Smad7 protein regulates the functional effects of TGFβ signaling during corneal wound healing. We tested that targeted delivery of Smad7 using recombinant adeno-associated virus serotype 5 (AAV5-Smad7) delivered to the corneal stroma can inhibit corneal haze post photorefractive keratectomy (PRK) in vivo in a rabbit corneal injury model. We demonstrate that a single topical application of AAV5-Smad7 in rabbit cornea post-PRK led to a significant decrease in corneal haze and corneal fibrosis. Further, histopathology revealed lack of immune cell infiltration following AAV5-Smad7 gene transfer into the corneal stroma. Our data demonstrates that AAV5-Smad7 gene therapy is relatively safe with significant potential for the treatment of corneal disease currently resulting in fibrosis and impaired vision