Assessment of anti-scarring therapies in ex vivo organ cultured rabbit corneas

Regenerative Therapy for Corneal Scarring Disorders

The cornea is a transparent and vitally multifaceted component of the eye, playing a pivotal role in vision and ocular health. It has primary refractive and protective functions. Typical corneal dysfunctions include opacities and deformities that result from injuries, infections, or other medical conditions. These can significantly impair vision. The conventional challenges in managing corneal ailments include the limited regenerative capacity (except corneal epithelium), immune response after donor tissue transplantation, a risk of long-term graft rejection, and the global shortage of transplantable donor materials. This review delves into the intricate composition of the cornea, the landscape of corneal regeneration, and the multifaceted repercussions of scar-related pathologies. It will elucidate the etiology and types of dysfunctions, assess current treatments and their limitations, and explore the potential of regenerative therapy that has emerged in both in vivo and clinical trials. This review will shed light on existing gaps in corneal disorder management and discuss the feasibility and challenges of advancing regenerative therapies for corneal stromal scarring.

Current Advances in Corneal Stromal Stem Cell Biology and Therapeutic Applications

Corneal stromal stem cells (CSSCs) are of particular interest in regenerative ophthalmology, offering a new therapeutic target for corneal injuries and diseases. This review provides a comprehensive examination of CSSCs, exploring their anatomy, functions, and role in maintaining corneal integrity. Molecular markers, wound healing mechanisms, and potential therapeutic applications are discussed. Global corneal blindness, especially in more resource-limited regions, underscores the need for innovative solutions. Challenges posed by corneal defects, emphasizing the urgent need for advanced therapeutic interventions, are discussed. The review places a spotlight on exosome therapy as a potential therapy. CSSC-derived exosomes exhibit significant potential for modulating inflammation, promoting tissue repair, and addressing corneal transparency. Additionally, the rejuvenation potential of CSSCs through epigenetic reprogramming adds to the evolving regenerative landscape. The imperative for clinical trials and human studies to seamlessly integrate these strategies into practice is emphasized. This points towards a future where CSSC-based therapies, particularly leveraging exosomes, play a central role in diversifying ophthalmic regenerative medicine.

NBL1 Reduces Corneal Fibrosis and Scar Formation after Wounding

Corneal scarring is a leading cause of blindness. Currently, there is no treatment to prevent and/or reduce corneal scar formation under pathological conditions. Our previous data showed that the NBL1 protein, also termed the DAN Family BMP (Bone morphogenetic protein) Antagonist, was highly expressed in corneal stromal cells upon wounding. Here, we examined the function of NBL1 in corneal wound healing. Mouse corneas were mechanically wounded, followed by a 2-week treatment using NBL1. Wounded corneas treated with vehicle or an Fc tag served as controls. Compared with the controls, NBL1 treatment facilitated wound re-epithelialization, partially restored the stromal thickness, and significantly reduced corneal scar formation. NBL1 treatment did not decrease immune cell infiltration, indicating that the anti-scarring effect was not dependent on immune suppression. We further examined the anti-fibrotic effect of NBL1 on human corneas. Pairs of human corneas were induced to form myofibroblasts (a key player in fibrosis and scarring) upon wounding and incubation in a medium containing TGF-β1. The OS corneas were treated with Fc as a control, and the OD corneas were treated with NBL1. Compared with the control, human corneas treated with NBL1 had significantly fewer myofibroblasts, which was consistent with these mouse data. A further study revealed that NBL1 treatment inhibited BMP canonical (phospho-Smad1/5) and no-canonical (phospho-p38) pathways in human corneas. Data show that NBL1 reduced corneal fibrosis and scar formation in mice and cultured human corneas. The underlying molecular mechanism is not certain because both anti-fibrotic Smad1/5 and pro-fibrotic p38 pathways were inhibited upon NBL1 treatment. Whether the p38 pathway dominates the Smad1/5 pathway during corneal fibrosis, leading to the anti-fibrotic effect of NBL1, needs further investigation.

The Efficacy of Atelocollagen to Inhibit Fibrotic Proliferation in Tenon Tissue: In vitro Study

INTRODUCTION

The aim of the study was to evaluate the safety and efficacy of atelocollagen in preventing the fibrotic change of human tenon tissue induced by transforming growth factor β1 (TGFβ1).

METHODS

Primary cultured human Tenon's fibroblasts (HTFs) were incubated with TGFβ1 alone and with various concentrations of atelocollagen, respectively. Cell viability was measured by Cell Counting Kit-8 (CCK-8). The mRNA levels of α-smooth muscle actin (α-SMA), vimentin, fibronectin, zonular occludens scaffolding protein (ZO-1), cellular communication network factor 2 (CCN2), and interleukin 6 (IL-6) were measured by quantitative reverse transcription polymerase chain reaction, Western blot, and immunofluorescence analysis. Wound healing assay and collagen contraction assay were additionally evaluated for identifying the inhibitory effect of atelocollagen in HTFs. To elucidate the mechanism by which atelocollagen affects HTF proliferation, the phospho-extracellular-signal-regulated kinases (pERK)/total-extracellular-signal-regulated kinases (tERK), phospho-focal adhesion kinase (pFAK)/total-focal adhesion kinase (tFAK), and pSmad3/tSmad3 protein expression ratios were measured by Western blot.

RESULTS

The safety of atelocollagen in HTF was identified by CCK-8 analysis. The expression of α-SMA and vimentin in HTFs treated with 0.023% and 0.046% atelocollagen significantly decreased at both mRNA and protein levels, while that of ZO-1 in 0.046% atelocollagen increased compared with TGFβ1-treated cells. The protein expression of fibronectin, CCN2, and IL-6 in HTFs treated with 0.023% and 0.046% atelocollagen significantly decreased. The immunofluorescence microscopy of α-SMA and ZO-1 showed results similar to those of the Western blot. In the wound-scratch assays, cell migration was significantly attenuated in HTFs treated with 0.005% atelocollagen. Atelocollagen at 0.005, 0.011, and 0.023% significantly inhibited the gel contraction induced by TGFβ1 at both 24 h and 48 h. The increase in pERK/tERK and pSmad3/tSmad3 protein expression ratios in TGFβ1-treated HTFs significantly decreased after treatment with 0.023 and 0.046% atelocollagen.

CONCLUSION

Since atelocollagen gel effectively suppresses the proliferation of HTFs in TGFβ1-induced transdifferentiation, it may be a potential therapeutic agent in glaucoma surgery.

Establishment of a Robust and Simple Corneal Organ Culture Model to Monitor Wound Healing

The use of in vitro systems to investigate the process of corneal wound healing offers the opportunity to reduce animal pain inflicted during in vivo experimentation. This study aimed to establish an easy-to-handle ex vivo organ culture model with porcine corneas for the evaluation and modulation of epithelial wound healing. Cultured free-floating cornea disks with a punch defect were observed by stereomicroscopic photo documentation. We analysed the effects of different cell culture media and investigated the impact of different wound sizes as well as the role of the limbus. Modulation of the wound healing process was carried out with the cytostatic agent Mitomycin C. The wound area calculation revealed that after three days over 90% of the lesion was healed. As analysed with TUNEL and lactate dehydrogenase assay, the culture conditions were cell protecting and preserved the viability of the corneal tissue. Wound healing rates differ dependent on the culture medium used. Mitomycin C hampered wound healing in a concentration-dependent manner. The porcine cornea ex vivo culture ideally mimics the in vivo situation and allows investigations of cellular behaviour in the course of wound healing. The effect of substances can be studied, as we have documented for a mitosis inhibitor. This model might aid in toxicological studies as well as in the evaluation of drug efficacy and could offer a platform for therapeutic approaches based on regenerative medicine.

Lycium barbarum Polysaccharide Suppresses Expression of Fibrotic Proteins in Primary Human Corneal Fibroblasts

(1) Objective: To study the anti-fibrotic effects of Lycium barbarum polysaccharides (LBP) on corneal stromal fibroblasts and assess LBP’s effect on cell viability. (2) Methods: Primary human corneal keratocytes of passage 3 to 6 were used for all experiments. Cells are pretreated with LBP solution for 24 h and then transforming growth factor beta 1 (TGFβ1) for 48 h and collected for experiments. Fibrotic protein analysis was performed using immunofluorescence and Western blot. The effect of LBP on cell viability was assessed using the MTS assay. (3) Results: LBP significantly reduced the expression of fibrotic proteins, including α-SMA and extracellular matrix proteins (collagen type I and III). LBP significantly decreased the viability of myofibroblasts but not the fibroblasts. Conclusions: In this study, LBP was effective in the prevention of fibrosis gene expression. Further studies to assess the underlying mechanism and pharmacological properties will facilitate the formation of a topical LBP solution for in vivo studies.

Corneal stromal wound healing: Major regulators and therapeutic targets

Corneal stromal wound healing is a complex event that occurs to restore the transparency of an injured cornea. It involves immediate apoptosis of keratocytes followed by their activation, proliferation, migration, and trans-differentiation to myofibroblasts. Myofibroblasts contract to close the wound and secrete extracellular matrix and proteinases to remodel it. Released proteinases may degenerate the basement membrane allowing an influx of cytokines from overlying epithelium. Immune cells infiltrate the wound to clear cellular debris and prevent infections. Gradually basement membrane regenerates, myofibroblasts and immune cells disappear, abnormal matrix is resorbed, and transparency of the cornea is restored. Often this cascade deregulates and corneal opacity results. Factors that prevent corneal opacity after an injury have always intrigued the researchers. They hold clinical relevance as they can guide the outcomes of corneal surgeries. Studies in the past have shed light on the role of various factors in stromal healing. TGFβ (transforming growth factor-beta) signaling is the central player guiding stromal responses. Other major regulators include myofibroblasts, basement membrane, collagen fibrils, small leucine-rich proteoglycans, biophysical cues, proteins derived from extracellular matrix, and membrane channels. The knowledge about their roles helped to develop novel therapies to prevent corneal opacity. This article reviews the role of major regulators that determine the outcome of stromal healing. It also discusses emerging therapies that modulate the role of these regulators to prevent stromal opacity.

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.

Systematic Review on Therapeutic Strategies to Minimize Corneal Stromal Scarring After Injury

OBJECTIVES

To evaluate recent studies on available and experimental therapies in preventing or minimizing corneal stromal scarring after injury.

METHODS

We performed an Entrez PubMed literature search using keywords "cornea," "scarring," "haze," "opacity," "ulcer," "treatments," "therapies," "treatment complications," and "pathophysiology" resulting in 390 articles of which 12 were analyzed after filtering, based on English language and publication within 8 years, and curation for relevance by the authors.

RESULTS

The 12 articles selected included four randomized control trials (RCTs) (two were double-blinded placebo-controlled RCTs, one was a prospective partially masked RCT, and one was an open-label RCT), two retrospective observational studies, and six laboratory-based studies including two studies having in vivo and in vitro experiments, one was in vivo study, one was ex vivo study, and the last two were in vitro studies. The current mainstay for preventing or minimizing corneal scarring involves the use of topical corticosteroids and local application of mitomycin C. However, supportive evidence for their use in clinical practice from well-designed RCTs is lacking. Laboratory studies on topical rosiglitazone therapy, vitamin C prophylaxis, gene therapy, and stem cell therapy have shown promising results but have yet to be translated to clinical research.

CONCLUSION

There is a need for more robust randomized controlled trials to support treatments using topical corticosteroids and mitomycin C. Furthermore, their clinical efficacy and safety profile should be compared with new treatments that have shown promising results in the laboratory setting. Ultimately, the goal should be to personalize cornea scarring treatment according to the most effective treatment for the specific underlying pathology.

Quercetin suppresses glomerulosclerosis and TGF‑β signaling in a rat model

The transforming growth factor-β (TGF-β) signaling pathway is an important regulatory pathway in renal fibrosis and is abnormally activated in glomerulosclerosis. Quercetin is a common Chinese herbal medicine and has been reported to inhibit TGF-β signaling pathway activation. In the present study a glomerulosclerosis rat model was constructed and mice were treated with different concentrations of quercetin. Biochemical parameters, pathological indices and expression levels of TGF-β signaling pathway-associated proteins were detected using immunohistochemistry and western blotting. It was demonstrated that quercetin significantly improved physiological indices and altered the expression levels of TGF-β signaling pathway-associated proteins in rats with glomerulosclerosis. In conclusion, quercetin can regulate the TGF-β signaling pathway and reduce the progression of glomerulosclerosis.

Tissue-derived microparticles reduce inflammation and fibrosis in cornea wounds

Biological materials derived from the extracellular matrix (ECM) of tissues serve as scaffolds for rebuilding tissues and for improved wound healing. Cornea trauma represents a wound healing challenge as the default repair pathway can result in fibrosis and scar formation that limit vision. Effective treatments are needed to reduce inflammation, promote tissue repair, and retain the tissue's native transparency and vision capacity. Tissue microparticles derived from cornea, cartilage and lymph nodes were processed and screened in vitro for their ability to reduce inflammation in ocular surface cells isolated from the cornea stroma, conjunctiva, and lacrimal gland. Addition of ECM particles to the media reduced expression of inflammatory genes and restored certain tear film protein production in vitro. Particles derived from lymph nodes were then applied to a rabbit lamellar keratectomy corneal injury model. Application of the tissue particles in a fibrin glue carrier decreased expression of inflammatory and fibrotic genes and scar formation as measured through imaging, histology and immunohistochemistry. In sum, immunomodulatory tissue microparticles may provide a new therapeutic tool for reducing inflammation in the cornea and ocular surface and promoting tissue repair. STATEMENT OF SIGNIFICANCE: Damaged cornea will result in scar tissue formation that impedes vision, and new therapies are needed to enhance wound healing in the cornea and to prevent fibrosis. We evaluated the effects of biological scaffolds derived extracellular matrix (ECM) during corneal wound healing. These ECM particles reduced inflammatory gene expression and restored tear film production in vitro, and reduced scar formation and fibrosis genes in the wounded cornea, when applied to in vivo lamellar keratectomy injury model. The immunomodulatory tissue microparticles may provide a new therapeutic tool for reducing inflammation in the cornea and ocular surface and promoting proper tissue repair.

Corneal chemical burn treatment through a delivery system consisting of TGF-β1 siRNA: in vitro and in vivo

Chemical burns are major causes of corneal blindness. Transforming growth factor beta-1 (TGFβ₁) plays an important role in induction of corneal inflammation-related-fibrosis leading to the blindness. Here, a topical delivery system consisting anti-fibrotic TGF-β₁ siRNA, an inflammatory suppressing gene, was designed for treatment of corneal injuries. TGF-β₁ siRNA loaded in nanoparticles (NPs) made up of polyethyleneimine polymer demonstrated high fibroblast transfection efficiency. Moreover, TGF-β₁ and PDGF genes and ECM deposition were suppressed in isolated human corneal fibroblasts. NPs inhibited proliferation and transformation of fibroblasts to myofibroblasts by S-phase arrest and α-SMA suppression in vitro, respectively. The mentioned finding was also confirmed in vivo, addressing high wound-healing potential of prepared gene delivery system which was superior to conventional betamethasone treatment. Besides, CD4⁺ and α-SMA antibody staining showed inhibited angiogenesis and myofibroblast accumulation in treated corneas. This study opens a new way for treating corneal fibrosis through topical siRNA delivery.

Nanostructured lipid carriers containing rapamycin for prevention of corneal fibroblasts proliferation and haze propagation after burn injuries: In vitro and in vivo

Chemical burns are a major cause of corneal haze and blindness. Corticosteroids are commonly used after corneal burns to attenuate the severity of the inflammation-related fibrosis. While research efforts have been aimed toward application of novel therapeutics. In the current study, a novel drug delivery system based nanostructured lipid carriers (NLCs) were designed to treat corneal alkaline burn injury. Rapamycin, a potent inhibitor of mammalian target of rapamycin pathway, was loaded in NLCs (rapa-NLCs), and the NLCs were characterized. Cell viability assay, cellular uptake of NLCs, and in vitro evaluation of the fibrotic/angiogenic genes suppression by rapa-NLCs were carried out on human isolated corneal fibroblasts. Immunohistochemistry (IHC) assays were also performed after treatment of murine model of corneal alkaline burn with rapa-NLCs. According to the results, rapamycin was efficiently loaded in NLCs. NLCs could enhance coumarin-6 fibroblast uptake by 1.5 times. Rapa-NLCs efficiently downregulated platelet-derived growth factor and transforming growth factor beta genes in vitro. Furthermore, proliferation of fibroblasts, a major cause of corneal haze after injury, reduced. IHC staining of treated cornea with alpha-smooth muscle actin and CD34 ⁺ antibodies showed efficient prevention of myofibroblasts differentiation and angiogenesis, respectively. In conclusion, ocular delivery of rapamycin using NLCs after corneal injury may be considered as a promising antifibrotic/angiogenic treatment approach to preserve patient eyesight.

Tranilast inhibits TGF-β-induced collagen gel contraction mediated by human corneal fibroblasts

AIM

To determine if tranilast affects human corneal fibroblast (HCFs) contraction.

METHODS

HCFs cultured in a three-dimensional type I collagen gel were treated with or without transforming growth factor beta (TGF-β) or tranilast. Gel diameter was measured as an indicator for collagen contraction. Immunoblot was performed to evaluate myosin light chain (MLC) and paxillin phosphorylation. Confocal microscopy was employed to examine the focal adhesions and actin stress fiber formation. Immunoblot analysis and gelatin zymography were performed to detect tissue inhibitors of metalloproteinases and matrix metalloproteinases (MMPs) in supernatant.

RESULTS

The inhibitory effect of tranilast on HCFs-mediated collagen gel contraction induced by TGF-β was dose-dependent. The significant effect of tranilast was started from 100 µmol/L and maximized at 300 µmol/L. The peak effect of 300 µmol/L tranilast also relied on the duration of treatment, which showed statistical significance from day 2. TGF-β-induced paxillin and MLC phosphorylation, stress fiber formation, focal adhesions, and MMP-1, MMP-2, and MMP-3 secretion in HCFs were also inhibited by tranilast.

CONCLUSION

Tranilast suppresses the HCFs-cultured collagen gel contraction induced by TGF-β. It attenuates actin stress fibers formation, focal adhesions, and the secretion of MMPs, with these actions likely contributing to the inhibitory effect on HCF contractility. By attenuating the contractility of corneal fibroblasts, tranilast treatment may inhibit corneal scarring.

Structuring of Hydrogels across Multiple Length Scales for Biomedical Applications

The development of new materials for clinical use is limited by an onerous regulatory framework, which means that taking a completely new material into the clinic can make translation economically unfeasible. One way to get around this issue is to structure materials that are already approved by the regulator, such that they exhibit very distinct physical properties and can be used in a broader range of clinical applications. Here, the focus is on the structuring of soft materials at multiple length scales by modifying processing conditions. By applying shear to newly forming materials, it is possible to trigger molecular reorganization of polymer chains, such that they aggregate to form particles and ribbon-like structures. These structures then weakly interact at zero shear forming a solid-like material. The resulting self-healing network is of particular use for a range of different biomedical applications. How these materials are used to allow the delivery of therapeutic entities (cells and proteins) and as a support for additive layer manufacturing of larger-scale tissue constructs is discussed. This technology enables the development of a range of novel materials and structures for tissue augmentation and regeneration.

Apratyramide, a Marine-Derived Peptidic Stimulator of VEGF-A and Other Growth Factors with Potential Application in Wound Healing

A novel linear depsipeptide enriched with tyrosine-derived moieties, termed apratyramide, was isolated from an apratoxin-producing cyanobacterium. The structure was determined using a combination of NMR spectroscopy, mass spectrometry, and chiral analysis of the acid hydrolyzate and confirmed by total synthesis. Apratyramide up-regulated multiple growth factors at the transcript level in human keratinocyte (HaCaT) cells and induced the secretion of vascular endothelial growth factor A (VEGF-A) from HaCaT cells, suggesting the compound's potential wound-healing properties through growth factor induction. Transcriptome analysis and sequential validation supported the hypothesis and indicated its mode of action (MOA) through the unfolded protein response (UPR) pathway, which is functionally related to wound healing and angiogenesis. The conditioned medium of HaCaT cells treated with apratyramide induced angiogenesis in vitro. An ex vivo rabbit corneal epithelial model was applied to confirm the VEGF-A induction in this wound-healing model.

Analysis of dermal fibroblasts isolated from neonatal and child cleft lip and adult skin: Developmental implications on reconstructive surgery

The nonsyndromic cleft is one of the most frequent congenital defects in humans. Clinical data demonstrated improved and almost scarless neonatal healing of reparative surgery. Based on our previous results on crosstalk between neonatal fibroblasts and adult keratinocytes, the present study focused on characterization of fibroblasts prepared from cleft lip tissue samples of neonates and older children, and compared them with samples isolated from normal adult skin (face and breast) and scars. Although subtle variances in expression profiles of children and neonates were observed, the two groups differed significantly from adult cells. Compared with adult cells, differences were observed in nestin and smooth muscle actin (SMA) expression at the protein and transcript level. Furthermore, fibroblast to myofibroblast differentiation drives effective wound healing and is largely regulated by the cytokine, transforming growth factor-β1 (TGF-β1). Dysregulation of the TGF-β signalling pathway, including low expression of the TGF-β receptor II, may contribute to reducing scarring in neonates. Fibroblasts of facial origin also exhibited age independent differences from the cells prepared from the breast, reflecting the origin of the facial cells from neural crest-based ectomesenchyme.

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

Wound healing is one of the most complex biological processes to occur in life. Repair of tissue following injury involves dynamic interactions between multiple cell types, growth factors, inflammatory mediators and components of the extracellular matrix (ECM). Aberrant and uncontrolled wound healing leads to a non-functional mass of fibrotic tissue. In the eye, fibrotic disease disrupts the normally transparent ocular tissues resulting in irreversible loss of vision. A common feature in fibrotic eye disease is the transdifferentiation of cells into myofibroblasts that can occur through a process known as epithelial-mesenchymal transition (EMT). Myofibroblasts rapidly produce excessive amounts of ECM and exert tractional forces across the ECM, resulting in the distortion of tissue architecture. Transforming growth factor-beta (TGFβ) plays a major role in myofibroblast transdifferentiation and has been implicated in numerous fibrotic eye diseases including corneal opacification, pterygium, anterior subcapsular cataract, posterior capsular opacification, proliferative vitreoretinopathy, fibrovascular membrane formation associated with proliferative diabetic retinopathy, submacular fibrosis, glaucoma and orbital fibrosis. This review serves to introduce the pathological functions of the myofibroblast in fibrotic eye disease. We also highlight recent developments in elucidating the multiple signaling pathways involved in fibrogenesis that may be exploited in the development of novel anti-fibrotic therapies to reduce ocular morbidity due to scarring.

Establishment of in vitro model of corneal scar pathophysiology

Corneal scarring is the major source of permanent blindness worldwide. The complex pathophysiology of corneal scarring is not comprehensibly understood as it involves the interaction of a constellation of pro-fibrotic cytokines influencing several signaling pathways involved in corneal scar development. In the present study, an attempt has been made to generate a relatively simple in vitro corneal scar model using primary corneal keratocytes by exogenously providing an optimized dose of combination of cytokines (TGF-β1, IL-6, and IL-8) involved in scar formation in situ. Data obtained from gene and protein expression analysis depicted enhanced ECM production with discrete expression of myofibroblast specific markers. The protein-protein interactions associated these proteins to various pathways involved in wound healing, cellular migration, and cytoskeletal remodeling justifying high relevance to in vivo scar formation. Hence the developed model can be used to acquire understanding about corneal scar pathophysiology and thus might be useful for designing the treatment modalities and efficacies for controlling scar formation.

Development of wound healing models to study TGFβ3's effect on SMA

The goal of this study was to test the efficacy of transforming growth factor beta 3 (TGFβ3) in reducing α-smooth muscle actin (SMA) expression in two models-an ex vivo organ culture and an in vitro 3D cell construct-both of which closely mimic an in vivo environment. For the ex vivo organ culture system, a central 6.0 mm corneal keratectomy was performed on freshly excised rabbit globes The corneas were then excised, segregated into groups treated with 1.0 ng/ml TGFβ1 or β3 (T1 or T3, respectively), and cultured for 2 weeks. The corneas were assessed for levels of haze and analyzed for SMA mRNA levels. For the 3D in vitro model, rabbit corneal fibroblasts (RbCFs) were cultured for 4 weeks on poly-transwell membranes in Eagle's minimum essential media (EMEM) + 10% FBS + 0.5 mM vitamin C ± 0.1 ng/ml T1 or T3. At the end of 4 weeks, the constructs were processed for analysis by indirect-immunofluorescence (IF) and RT-qPCR. The RT-qPCR data showed that SMA mRNA expression in T3 samples for both models was significantly lower (p < 0.05) than T1 treatment (around 3-fold in ex vivo and 2-fold in constructs). T3 also reduced the amount of scarring in ex vivo corneas as compared with the T1 samples. IF data from RbCF constructs confirmed that T3-treated samples had up to 4-fold (p < 0.05) lower levels of SMA protein expression than samples treated with T1. These results show that T3 when compared to T1 decreases the expression of SMA in both ex vivo organ culture and in vitro 3D cell construct models. Understanding the mechanism of T3's action in these systems and how they differ from simple cell culture models, may potentially help in developing T3 as an anti-scarring therapy.

Custom RT-qPCR-array for glaucoma filtering surgery prognosis

Excessive subconjunctival scarring is the main reason of failure of glaucoma filtration surgery. We analyzed conjunctival and systemic gene expression patterns after non penetrating deep sclerectomy (NPDS). To find expression patterns related to surgical failure and their correlation with the clinical outcomes. This study consisted of two consecutive stages. The first was a prospective analysis of wound-healing gene expression profile of six patients after NPDS. Conjunctival samples and peripheral blood samples were collected before and 15, 90,180, and 360 days after surgery. In the second stage, we conducted a retrospective analysis correlating the late conjunctival gene expression and the outcome of the NPDS for 11 patients. We developed a RT-qPCR Array for 88 key genes associated to wound healing. RT-qPCR Array analysis of conjunctiva samples showed statistically significant differences in 29/88 genes in the early stages after surgery, 20/88 genes between 90 and 180 days after surgery, and only 2/88 genes one year after surgery. In the blood samples, the most important changes occurred in 12/88 genes in the first 15 days after surgery. Correspondence analyses (COA) revealed significant differences between the expression of 20/88 genes in patients with surgical success and failure one year after surgery. Different expression patterns of mediators of the bleb wound healing were identified. Examination of such patterns might be used in surgery prognosis. RT-qPCR Array provides a powerful tool for investigation of differential gene expression wound healing after glaucoma surgery.

Connective tissue growth factor is not necessary for haze formation in excimer laser wounded mouse corneas

We sought to determine if connective tissue growth factor (CTGF) is necessary for the formation of corneal haze after corneal injury. Mice with post-natal, tamoxifen-induced, knockout of CTGF were subjected to excimer laser phototherapeutic keratectomy (PTK) and the corneas were allowed to heal. The extent of scaring was observed in non-induced mice, heterozygotes, and full homozygous knockout mice and quantified by macrophotography. The eyes from these mice were collected after euthanization for re-genotyping to control for possible Cre-mosaicism. Primary corneal fibroblasts from CTGF knockout corneas were established in a gel plug assay. The plug was removed, simulating an injury, and the rate of hole closure and the capacity for these cells to form light reflecting cells in response to CTGF and platelet-derived growth factor B (PDGF-B) were tested and compared to wild-type cells. We found that independent of genotype, each group of mice was still capable of forming light reflecting haze in the cornea after laser ablation (p = 0.40). Results from the gel plug closure rate in primary cell cultures of knockout cells were not statistically different from serum starved wild-type cells, independent of treatment. Compared to the serum starved wild-type cells, stimulation with PDGF-BB significantly increased the KO cell culture’s light reflection (p = 0.03). Most interestingly, both reflective cultures were positive for α-SMA, but the cellular morphology and levels of α-SMA were distinct and not in proportion to the light reflection seen. This new work demonstrates that corneas without CTGF can still form sub-epithelial haze, and that the light reflecting phenotype can be reproduced in culture. These data support the possibilities of growth factor redundancy and that multiple pro-haze pathways exist.

Development and Assessment of a Novel Canine Ex Vivo Corneal Model

PURPOSE

To develop a novel ex vivo extended culture model of canine corneal epithelial cell wound healing.

MATERIALS AND METHODS

Canine corneoscleral rims (CSR) were obtained and, after preparation for culture, were placed on a nutating scaffold and incubated in physiological conditions. In experiment 1, eight CSR in a serum-containing antimicrobial-fortified medium were monitored for epithelial integrity and bacterial infection up to 28 days in culture. CSR were assessed histologically at the end of the culture period end points 0, 7, 14, and 28 days with accompanying scanning electron microscopic (SEM) and transmission electron microscopic (TEM) evaluation. Samples for microbial culture were obtained at days 0, 3, 7, 14, and 28. In experiment 2, uniform 8-mm-diameter superficial corneal epithelial wounds were created and monitored for re-epithelialization in the same culture conditions or in a serum-free protein equivalent medium, with four CSR per group. Standardized digital images were obtained with cobalt filter at the time of fluorescein staining and media change every six hours. Image J imaging software was used to measure the area of fluorescein retention. Re-epithelialization rates were calculated and CSR then fixed for immunohistochemistry (IHC).

RESULTS

All corneas survived to end points as described in experiment 1 with no evidence of contamination or compromised epithelial integrity. Histologically, a multilayered epithelium was maintained and corneal edema was not appreciated until day 14. SEM examination revealed epithelial cell layer confluence and migrating epithelial cells of normal cellular morphology with normal cell-cell interactions on TEM. In experiment 2, all eight corneas healed with a healing rate of 0.702 ± 0.130 mm²/h (1.25 mm/day epithelial cell migration rate) and were positive in IHC evaluation for markers of corneal fibrosis.

CONCLUSION

This ex vivo canine corneal wound healing model is an appropriate and clinically relevant tool for assessment and modulation of epithelial wound healing.

Commonly Used Animal Models

This chapter provides an introduction to animals that are commonly used for research. It presents information on basic care topics such as biology, behavior, housing, feeding, sexing, and breeding of these animals. The chapter provides some insight into the reasons why these animals are used in research. It also gives an overview of techniques that can be utilized to collect blood or to administer drugs or medicine. Each section concludes with a brief description of how to recognize abnormal signs, in addition to lists of various diseases.

Ex vivo rabbit and human corneas as models for bacterial and fungal keratitis

PURPOSE

In the study of microbial keratitis, in vivo animal models often require a large number of animals, and in vitro monolayer cell culture does not maintain the three-dimensional structure of the tissues or cell-to-cell communication of in vivo models. Here, we propose reproducible ex vivo models of single- and dual-infection keratitis as an alternative to in vivo and in vitro models.

METHODS

Excised rabbit and human corneoscleral rims maintained in organ culture were infected using 10⁸ cells of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans or Fusarium solani. The infection was introduced by wounding with a scalpel and exposing corneas to the microbial suspension or by intrastromal injection. Post-inoculation, corneas were maintained for 24 and 48 h at 37 °C. After incubation, corneas were either homogenised to determine colony-forming units (CFU)/cornea or processed for histological examination using routine staining methods. Single- and mixed-species infections were compared.

RESULTS

We observed a significant increase in CFU after 48 h compared to 24 h with S. aureus and P. aeruginosa. However, no such increase was observed in corneas infected with C. albicans or F. solani. The injection method yielded an approximately two- to 100-fold increase (p < 0.05) in the majority of organisms from infected corneas. Histology of the scalpel-wounded and injection models indicated extensive infiltration of P. aeruginosa throughout the entire cornea, with less infiltration observed for S. aureus, C. albicans and F. solani. The models also supported dual infections.

CONCLUSIONS

Both scalpel wounding and injection methods are suitable for inducing infection of ex vivo rabbit and human cornea models. These simple and reproducible models will be useful as an alternative to in vitro and in vivo models for investigating the detection and treatment of microbial keratitis, particularly when this might be due to two infective organisms.

Cornea As a Model for Testing CTGF-Based Antiscarring Drugs

Scarring remains a serious complication of the wound healing process that can lead to the formation of excessive fibrous connective tissue in an organ or tissue leading to pain and loss of function. This process is mainly regulated by Transforming growth factor β1 (TGF-β1), which binds to receptors and induces its downstream mediator, Connective tissue growth factor (CTGF). The number of drugs targeting CTGF for treating scars has been on the rise in the past few years. The purpose of this article is to suggest the possibility of using cornea as a model for testing anti-CTGF therapies for scarring.

Human Serum Eye Drops in Eye Alterations: An Insight and a Critical Analysis

Human serum contains a physiological plethora of bioactive elements naturally released by activated platelets which might have a significant effect on the regeneration of corneal layers by stimulating the cell growth. This mechanism supported the use of human serum eye drops in some ocular diseases associated with dystrophic changes and alterations of the tear film, such as persistent corneal epithelial defects and dry eye syndrome. We focused our effort on potential benefits and limitations of the use of human serum eye drops when conventional therapies failed. We reviewed the recent literature by reporting published studies from 2010 to 2014. Despite the limited evaluated study populations, most of the clinical studies have confirmed that serum eye drop therapy is effective in corneal healing by reducing ocular symptom, particularly during the short-term follow-up. In addition, three recent published studies have shown the efficacy of the serum eye drop therapy in comparison to traditional ones in intractable patients. Besides, reported ongoing clinical studies confirmed the open debate regarding the use of biologic tools for cornea regeneration. Results from these studies might open novel challenges and perspectives in the therapy of such refractory patients.

Progress in corneal wound healing

Corneal wound healing is a complex process involving cell death, migration, proliferation, differentiation, and extracellular matrix remodeling. Many similarities are observed in the healing processes of corneal epithelial, stromal and endothelial cells, as well as cell-specific differences. Corneal epithelial healing largely depends on limbal stem cells and remodeling of the basement membrane. During stromal healing, keratocytes get transformed to motile and contractile myofibroblasts largely due to activation of transforming growth factor-β (TGF-β) system. Endothelial cells heal mostly by migration and spreading, with cell proliferation playing a secondary role. In the last decade, many aspects of wound healing process in different parts of the cornea have been elucidated, and some new therapeutic approaches have emerged. The concept of limbal stem cells received rigorous experimental corroboration, with new markers uncovered and new treatment options including gene and microRNA therapy tested in experimental systems. Transplantation of limbal stem cell-enriched cultures for efficient re-epithelialization in stem cell deficiency and corneal injuries has become reality in clinical setting. Mediators and course of events during stromal healing have been detailed, and new treatment regimens including gene (decorin) and stem cell therapy for excessive healing have been designed. This is a very important advance given the popularity of various refractive surgeries entailing stromal wound healing. Successful surgical ways of replacing the diseased endothelium have been clinically tested, and new approaches to accelerate endothelial healing and suppress endothelial-mesenchymal transformation have been proposed including Rho kinase (ROCK) inhibitor eye drops and gene therapy to activate TGF-β inhibitor SMAD7. Promising new technologies with potential for corneal wound healing manipulation including microRNA, induced pluripotent stem cells to generate corneal epithelium, and nanocarriers for corneal drug delivery are discussed. Attention is also paid to problems in wound healing understanding and treatment, such as lack of specific epithelial stem cell markers, reliable identification of stem cells, efficient prevention of haze and stromal scar formation, lack of data on wound regulating microRNAs in keratocytes and endothelial cells, as well as virtual lack of targeted systems for drug and gene delivery to select corneal cells.