Reprint of "Dynamics of the expression of intermediate filaments vimentin and desmin during myofibroblast differentiation after corneal injury"

Anterior blepharitis is associated with elevated plectin levels consistent with a pronounced intracellular response

PURPOSE

Anterior blepharitis is a frequent ocular condition which may result in severe ocular surface disease. In this study, advanced proteome analysis was performed to elucidate biological mechanisms underlying anterior blepharitis.

METHODS

All patients underwent full ophthalmological examination including Ocular Surface Disease Index score (OSDI). Measurement of non-invasive break-up time (NBUT), Oxford score, and meibography were performed. Tear film samples from treatment naïve patients with anterior blepharitis (n = 15) and age-matched controls (n = 11) were collected with Schirmer filtration paper. The samples were analyzed with label-free quantification nano liquid chromatography - tandem mass spectrometry (LFQ nLC-MS/MS). Significantly regulated proteins were identified with a permutation-based calculation with a false discovery rate at 0.05.

RESULTS

Among the 927 proteins detected, a total of 162 proteins were significantly changed. Regulated proteins were involved in cytoplasmic translation, positive regulation of B cell activation, complement activation and phagocytosis. High levels of plakin proteins, a group of proteins involved in cytoskeleton organization, were observed in anterior blepharitis, including plectin, desmoplakin, envoplakin, epiplakin, periplakin, and vimentin. The upregulation of plectin was confirmed with single reaction monitoring. Patients with anterior blepharitis had lower levels of immunoglobulin chains, VEGF coregulated chemokine 1 (CXCL17), and platelet-derived growth factor C.

CONCLUSIONS

Anterior blepharitis was associated with a high level of plectin indicating a pronounced intracellular response with cytoskeletal reorganization. Our data suggest a lack of immunoglobulin chains and CXCL17 in anterior blepharitis with potential alterations in the ocular surface immune response.

The senescence difference between the central and peripheral cornea induced by sutures

INTRODUCTION

Cell senescence plays a regulatory role in tissue fibrosis. Corneal scarring is usually more severe in the central cornea based on clinical observation. In this study, we attempted to explore the senescence difference between the central and peripheral cornea in an in vivo mouse model with suture-induced senescence and in an in vitro model of senescence with hydrogen peroxide (H₂O₂)-induced rabbit corneal fibroblasts.

METHODS

Male Balb/c mice (6-8 weeks) received sutures in the central, superior, inferior, nasal, and temporal cornea. The sutures were removed on the 14th day. Corneal neovascularization was observed under a slit lamp microscope with a digital camera. The fibroblasts isolated from the central and peripheral rabbit cornea were induced with H₂O₂ to establish the senescence model in vitro. Senescence was evaluated with SA-β-gal staining and gene expression analysis of p21, p27, and p53.

RESULTS

Senescent cells accumulated in the corneal stroma from the third day to the 14th day after the operation and peaked on the 14th day. More senescent keratocytes were observed in the peripheral cornea of the mouse model. In vitro, the peripheral corneal fibroblasts were more prone to senescence due to H₂O₂. The polymerase chain reaction results showed that the senescence-related genes p21, p27, and p53 were highly expressed in the peripheral corneal fibroblasts compared with the central corneal fibroblasts.

CONCLUSIONS

Senescent fibroblasts can limit tissue fibrosis; hence, the senescence difference between the central and peripheral cornea may contribute to the difference in scarring.

Microstructured collagen films for 3D corneal stroma modelling

PURPOSE/AIM

Corneal injury is a major cause of impaired vision around the globe. The fine structure of the corneal stroma plays a pivotal role in the phenotype and behavior of the embedded cells during homeostasis and healing after trauma or infection. In order to study healing processes in the cornea, it is important to create culture systems that functionally mimic the natural environment.

MATERIALS AND METHODS

Collagen solution was vitrified on top of a grated film to achieve thin collagen films with parallel microgrooves. Keratocytes (corneal stromal cells) were cultured on the films either as a single layer or as stacked layers of films and cells. SEM and F-actin staining were used to analyze the pattern transference onto the collagen and the cell orientation on the films. Cell viability was analyzed with MTS and live/dead staining. Keratocytes, fibroblasts, and myofibroblasts were cultured to study the pattern's effect on phenotype.

RESULTS

A microstructured collagen film-based culture system that guides keratocytes (stromal cells) to their native, layerwise perpendicular orientation in 3D and that can support fibroblasts and myofibroblasts was created. The films are thin and transparent enough to observe cells at least three layers deep. The cells maintain viability in 2D and 3D cultures and the films can support fibroblast and myofibroblast phenotypes.

CONCLUSIONS

The films provide an easily reproducible stroma model that maintains high cell viability and improves the preservation of the keratocyte phenotype in keratocytes that are differentiated to fibroblasts.

BMP3 inhibits TGFβ2-mediated myofibroblast differentiation during wound healing of the embryonic cornea

Often acute damage to the cornea initiates drastic tissue remodeling, resulting in fibrotic scarring that disrupts light transmission and precedes vision impairment. Very little is known about the factors that can mitigate fibrosis and promote scar-free cornea wound healing. We previously described transient myofibroblast differentiation during non-fibrotic repair in an embryonic cornea injury model. Here, we sought to elucidate the mechanistic regulation of myofibroblast differentiation during embryonic cornea wound healing. We found that alpha-smooth muscle actin (αSMA)-positive myofibroblasts are superficial and their presence inversely correlates with wound closure. Expression of TGFβ2 and nuclear localization of pSMAD2 were elevated during myofibroblast induction. BMP3 and BMP7 were localized in the corneal epithelium and corresponded with pSMAD1/5/8 activation and absence of myofibroblasts in the healing stroma. In vitro analyses with corneal fibroblasts revealed that BMP3 inhibits the persistence of TGFβ2-induced myofibroblasts by promoting disassembly of focal adhesions and αSMA fibers. This was confirmed by the expression of vinculin and pFAK. Together, these data highlight a mechanism to inhibit myofibroblast persistence during cornea wound repair.

Are miRNAs Dynamic Biomarkers in Keratoconus? A Review of the Literature

Aim: A review of miRNA (microRNA) profiling studies in keratoconus. Methods: Literature search strategy—PubMed central database, using miRNA or microRNA and keratoconus as keywords. Results: Eleven experimental or clinical studies on humans regarding miRNA and keratoconus, published in English between 2009 and 2020 were retrieved. Conclusion: The publications regarding the role of miRNAs in keratoconus are scarce and diverse but provide some valuable information about potential new mechanisms of keratoconus development and progression. The cornea expresses almost 300 different miRNAs, 18 of which are specific, and miR-184 is by far the most abundant, with expression restricted to central basal and suprabasal epithelial cells. Mutations in the seed region of MIR184 were proved to be rare and nonspecific in patients with isolated keratoconus. Overall, in keratoconus, a total of 29 miRNAs were upregulated, and 11 were downregulated. It appeared that miR-143-3p, miR-182-5p, and miR-92a-3p were highly expressed, while the miRNAs connected to cell–cell junction, cell division, and motor activity were downregulated. In less advanced forms, altered expression of four miRNAs—miR-151a-3p, miR-194-5p, miR-195-5p, miR-185-5p—was proved in the cone epithelium; in contrast, in advanced keratoconus, the expression of miR-151a-3p and miR-194-5p remained altered, changes in the expression of miR-195 and miR-185 were not reported, and the expression of miR-138-5p, miR-146b-5p, miR-28-5p, and miR-181a-2-3p was also altered in the corneal epithelium. Keratoconus is a dynamic process of corneal stromal thinning that might result from a dynamic miRNA expression in the corneal epithelium exposed to environmental and behavioral factors causing repetitive traumas. Further experimental studies are needed to prove this hypothesis.

Low-dose Aspirin prevents hypertension and cardiac fibrosis when thromboxane A2 is unrestrained

Enhanced platelet activation has been reported in patients with essential hypertension and heart failure. The possible contribution of platelet-derived thromboxane (TX)A2 in their pathophysiology remains unclear. We investigated the systemic TXA2 biosynthesis in vivo and gene expression of its receptor TP in 22 essential hypertension patients and a mouse model of salt-sensitive hypertension. The contribution of platelet TXA2 biosynthesis on enhanced blood pressure (BP) and overload-induced cardiac fibrosis was explored in mice by treating with low-dose Aspirin, resulting in selective inhibition of platelet cyclooxygenase (COX)-1-dependent TXA2 generation. In essential hypertensive patients, systemic biosynthesis of TXA2 [assessed by measuring its urinary metabolites (TXM) reflecting predominant platelet source] was enhanced together with higher gene expression of circulating leukocyte TP and TGF-β, vs. normotensive controls. Similarly, in hypertensive mice with prostacyclin (PGI2) receptor (IP) deletion (IPKO) fed with a high-salt diet, enhanced urinary TXM, and left ventricular TP overexpression were detected vs. normotensive wildtype (WT) mice. Increased cardiac collagen deposition and profibrotic gene expression (including TGF-β) was found. Low-dose Aspirin administration caused a selective inhibition of platelet TXA2 biosynthesis and mitigated enhanced blood pressure, cardiac fibrosis, and left ventricular profibrotic gene expression in IPKO but not WT mice. Moreover, the number of myofibroblasts and extravasated platelets in the heart was reduced. In cocultures of human platelets and myofibroblasts, platelet TXA2 induced profibrotic gene expression, including TGF-β1. In conclusion, our results support tailoring low-dose Aspirin treatment in hypertensive patients with unconstrained TXA2/TP pathway to reduce blood pressure and prevent early cardiac fibrosis.

Effect of isolation method on human corneal stromal cell behaviour

Current research on healthy corneal stromal cells will typically use primary cells as they are the most representative of in vivo behaviour. Primary cells are normally isolated from the limbus of discarded donor peripheral corneal tissue left over from transplantation (due to its relative abundance). Therefore, the central part of the cornea is less used in research as this tissue is usually used for transplantation. In some cases, although rare, the whole cornea, can become available for research. It is important to keep in mind that these corneas often have longer storage time, but the use of the central tissue for research is even more interesting, as knowing what cells are being transplanted into recipients would be highly relevant. To this end, stromal cells were extracted from both the limbus and central button of healthy corneas donated for research. This allowed for important comparison between central and limbal cells in culture. Of interest here was the extraction method of stromal cells from the donor tissue. The two most common methods of extraction are enzyme digestion and explant migration. However, no work has been done to understand how each method relatively affects the extracted cells. The extraction method and location from which stromal cells are harvested seems to have a significant effect on the cell adherence, survival, and gene expression of the stromal cells in culture. Enzyme digested cells showed that limbal and central cells had different gene expressions prior to culture, with gene such as ALDH3A1 being much more expressed in limbal cells. Enzyme digesting the limbal ring seems to yield the hardiest populations of stromal cells, a desirable trait in the culture of primary cells.

Corneal myofibroblasts and fibrosis

Myofibroblasts are alpha-smooth muscle actin (SMA)+ cells that have a critical role in the corneal stromal response to infections, injuries, and surgeries, and which produce corneal scarring fibrosis when they develop in excess. These contractile and opaque cells-produce large amounts of disordered extracellular matrix (ECM)-and develop from keratocyte-derived corneal fibroblasts or bone marrow-derived fibrocytes, and possibly other cell types, in response to TGFβ1, TGFβ2 and PDGF from the epithelium, tears, endothelium, and other stromal cells. Recent proteomic analyses have revealed that the myofibroblasts that develop from different progenitors aren't interchangeable, but have major differences in protein expression and functions. Absence or defective regeneration of the epithelial basement membrane (EBM) and/or Descemet's basement membrane (DBM) results in development and persistence of myofibroblasts in the corneal stroma. The functions of myofibroblasts in the cornea include production of volume-additive ECM, tissue contraction, production of various growth factors, cytokines and chemokines that regulate stromal cells, including other myofibroblasts, production of collagenases and metalloproteinases involved in tissue remodeling, and the expression of toll-like receptors that likely have critical roles in the clearance of bacteria and viruses causing corneal infections.

Expression of Langerin/CD 207 and α-smooth muscle actin in ex vivo rabbit corneal keratitis model

The constant exposure of ocular surface to external environment and then to several microbial agents is often related to the pathogenesis of various inflammatory eye disorders. In the present study α-Smooth Muscle Actin (α-SMA) and Langerin CD/207 expression and function was investigated in a rabbit corneal keratitis. The inflammation was induced by the secreted form of glycoprotein B (gB1s) of HSV-1, in an ex vivo rabbit corneal model. α-SMA is often used as a marker for myofibroblasts. In this study, for the first time, we show α-SMA positive corneal epithelial cells, during HSV-1 cornea inflammation, demonstrating a crucial role in wound healing, especially during remodeling phase. Furthermore, we show the presence of Dendritic Cells Langerin CD/207 positive, located mainly in the basal epithelial layer and in corneal stroma during the inflammatory processes. Our result validating the ex vivo organotypic rabbit corneal model, for the study about pathogenesis of HSV-1 ocular infection.

Corneal Cells: Fine-tuning Nerve Regeneration

The cornea is a transparent outermost structure of the eye anterior segment comprising the highest density of innervated tissue. In the process of corneal innervation, trigeminal ganglion originated corneal nerves diligently traverse different corneal cell types in different corneal layers including the corneal stroma and epithelium. While crossing the stromal and epithelial cell layers during innervation, due to the existing physical contacts, close interactions occur between stromal keratocytes, epithelial cells, resident immune cells and corneal nerves. Furthermore, by producing various trophic and growth factors corneal cells assist in maintaining the growth and function of corneal nerves. Similarly, corneal nerve generated growth factors critically modify the corneal cell function in all the corneal layers. Due to their close association and contacts, on-going cross-communication between these cell types and corneal nerves play a vital role in the modulation of corneal nerve function, regeneration during wound healing. The present review highlights the influence of different corneal cell types and growth factors released from these cells on corneal nerve regeneration and function.

Biomaterials and controlled release strategy for epithelial wound healing

The skin and cornea are tissues that provide protective functions. Trauma and other environmental threats often cause injuries, infections and damage to these tissues, where the degree of injury is directly correlated to the recovery time. For example, a superficial skin or corneal wound may recover within days; however, more severe injuries can last up to several months and may leave scarring. Thus, therapeutic strategies have been introduced to enhance the wound healing efficiency and quality. Although the skin and cornea share similar anatomic structures and wound healing process, therapeutic agents and formulations for skin and cornea wound healing differ in accordance with the tissue and wound type. In this review, we describe the anatomy and epithelial wound healing processes of the skin and cornea, and summarize the therapeutic molecules that are beneficial to the respective regeneration process. In addition, biomaterial scaffolds that inherently possess bioactive properties or modified with therapeutic molecules for topical controlled release and enhanced wound healing efficiency are also discussed.

Tissue and cellular biomechanics during corneal wound injury and repair

Corneal wound healing is an enormously complex process that requires the simultaneous cellular integration of multiple soluble biochemical cues, as well as cellular responses to the intrinsic chemistry and biophysical attributes associated with the matrix of the wound space. Here, we document how the biomechanics of the corneal stroma are altered through the course of wound repair following keratoablative procedures in rabbits. Further we documented the influence that substrate stiffness has on stromal cell mechanics. Following corneal epithelial debridement, New Zealand white rabbits underwent phototherapeutic keratectomy (PTK) on the right eye (OD). Wound healing was monitored using advanced imaging modalities. Rabbits were euthanized and corneas were harvested at various time points following PTK. Tissues were characterized for biomechanics with atomic force microscopy and with histology to assess inflammation and fibrosis. Factor analysis was performed to determine any discernable patterns in wound healing parameters. The matrix associated with the wound space was stiffest at 7days post PTK. The greatest number of inflammatory cells were observed 3days after wounding. The highest number of myofibroblasts and the greatest degree of fibrosis occurred 21days after wounding. While all clinical parameters returned to normal values 400days after wounding, the elastic modulus remained greater than pre-surgical values. Factor analysis demonstrated dynamic remodeling of stroma occurs between days 10 and 42 during corneal stromal wound repair. Elastic modulus of the anterior corneal stroma is dramatically altered following PTK and its changes coincide initially with the development of edema and inflammation, and later with formation of stromal haze and population of the wound space with myofibroblasts. Factor analysis demonstrates strongest correlation between elastic modulus, myofibroblasts, fibrosis and stromal haze thickness, and between edema and central corneal thickness.

STATEMENT OF SIGNIFICANCE

Tissue biomechanics during the course of corneal wound healing is documented for the first time through atomic force microscopy, and is correlated with advanced clinical imaging and immunohistochemistry. Parameters obtained from the study are applied in a multivariate statistical model to cluster the data for better classification and monitor the wound repair process. Elastic modulus of the anterior corneal stroma is dramatically altered following wounding and correlates initially with the development of edema and inflammation, and later with formation of stromal haze and population of the wound space with myofibroblasts. Importantly, the occurrence of myofibroblasts is preceded by changes in tissue mechanics, which is important to consider in light of crosslinking procedures applied to treat corneal diseases.

Acacia honey accelerates in vitro corneal ulcer wound healing model

BACKGROUND

The study aimed to evaluate the effects of Acacia honey (AH) on the migration, differentiation and healing properties of the cultured rabbit corneal fibroblasts.

METHODS

Stromal derived corneal fibroblasts from New Zealand White rabbit (n = 6) were isolated and cultured until passage 1. In vitro corneal ulcer was created using a 4 mm corneal trephine onto confluent cultures and treated with basal medium (FD), medium containing serum (FDS), with and without 0.025 % AH. Wound areas were recorded at day 0, 3 and 6 post wound creation. Genes and proteins associated with wound healing and differentiation such as aldehyde dehydrogenase (ALDH), vimentin, alpha-smooth muscle actin (α-SMA), collagen type I, lumican and matrix metalloproteinase 12 (MMP12) were evaluated using qRT-PCR and immunocytochemistry respectively.

RESULTS

Cells cultured with AH-enriched FDS media achieved complete wound closure at day 6 post wound creation. The cells cultured in AH-enriched FDS media increased the expression of vimentin, collagen type I and lumican genes and decreased the ALDH, α-SMA and MMP12 gene expressions. Protein expression of ALDH, vimentin and α-SMA were in accordance with the gene expression analyses.

CONCLUSION

These results demonstrated AH accelerate corneal fibroblasts migration and differentiation of the in vitro corneal ulcer model while increasing the genes and proteins associated with stromal wound healing.

ITF2357 transactivates Id3 and regulate TGFβ/BMP7 signaling pathways to attenuate corneal fibrosis

Corneal fibrosis is often seen in patients with ocular trauma and infection that compromises corneal transparency resulting in vision loss. Treatment strategies including NSAIDs, steroids, MMC and corneal transplants have shown tremendous success but with several side effects and cellular toxicity. Histone deacetylase inhibitors (HDACi) have been shown to inhibit corneal fibrosis via TGFβ signaling pathway. In this study, we investigated safety, efficacy and mechanism of action of a HDACi, ITF2357 in TGFβ-stimulated in vitro primary human cornea stromal fibroblasts (pHCSFs) and in vivo in a photorefractive keratectomy-treated rabbit model of corneal fibrosis. We found that in vivo ITF2357 decreased collagen I, collagen IV, fibronectin, integrin αVβ3 expression with a reduction in corneal haze. In addition, ITF2357 reduced myofibroblast formation, suppressed phosphorylation of Smad proteins in TGFβ pathway and inhibited key responsive protein, P4HA1 involved in pro-collagen synthesis. Treatment of pHCSFs with ITF2357 activated BMP7 levels and expressed all the members of inhibitor of differentiation proteins (Id1-Id4), however, it failed to rescue TGFβ-driven transdifferentiation of fibroblasts to myofibroblasts in the presence of siRNA specific to Id3. We conclude that ITF2357 is a potential anti-fibrotic drug that exerts its action via activation of Id3, a downstream target of TGFβ/BMP7 signaling pathways.

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.

Nanomedicine approaches for corneal diseases

Corneal diseases are the third leading cause of blindness globally. Topical nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics and tissue transplantation are currently used to treat corneal pathological conditions. However, barrier properties of the ocular surface necessitate high concentration of the drugs applied in the eye repeatedly. This often results in poor efficacy and several side-effects. Nanoparticle-based molecular medicine seeks to overcome these limitations by enhancing the permeability and pharmacological properties of the drugs. The promise of nanomedicine approaches for treating corneal defects and restoring vision without side effects in preclinical animal studies has been demonstrated. Numerous polymeric, metallic and hybrid nanoparticles capable of transporting genes into desired corneal cells to intercept pathologic pathways and processes leading to blindness have been identified. This review provides an overview of corneal diseases, nanovector properties and their applications in drug-delivery and corneal disease management.

Hevin plays a pivotal role in corneal wound healing

Background

Hevin is a matricellular protein involved in tissue repair and remodeling via interaction with the surrounding extracellular matrix (ECM) proteins. In this study, we examined the functional role of hevin using a corneal stromal wound healing model achieved by an excimer laser-induced irregular phototherapeutic keratectomy (IrrPTK) in hevin-null (hevin^-/-) mice. We also investigated the effects of exogenous supplementation of recombinant human hevin (rhHevin) to rescue the stromal cellular components damaged by the excimer laser.

Methodology/Principal Findings

Wild type (WT) and hevin^-/- mice were divided into three groups at 4 time points- 1, 2, 3 and 4 weeks. Group I served as naïve without any treatment. Group II received epithelial debridement and underwent IrrPTK using excimer laser. Group III received topical application of rhHevin after IrrPTK surgery for 3 days. Eyes were analyzed for corneal haze and matrix remodeling components using slit lamp biomicroscopy, in vivo confocal microscopy, light microscopy (LM), transmission electron microscopy (TEM), immunohistochemistry (IHC) and western blotting (WB). IHC showed upregulation of hevin in IrrPTK-injured WT mice. Hevin^-/- mice developed corneal haze as early as 1-2 weeks post IrrPTK-treatment compared to the WT group, which peaked at 3-4 weeks. They also exhibited accumulation of inflammatory cells, fibrotic components of ECM proteins and vascularized corneas as seen by IHC and WB. LM and TEM showed activated keratocytes (myofibroblasts), inflammatory debris and vascular tissues in the stroma. Exogenous application of rhHevin for 3 days reinstated inflammatory index of the corneal stroma similar to WT mice.

Conclusions/Significance

Hevin is transiently expressed in the IrrPTK-injured corneas and loss of hevin predisposes them to aberrant wound healing. Hevin^-/- mice develop early corneal haze characterized by severe chronic inflammation and stromal fibrosis that can be rescued with exogenous administration of rhHevin. Thus, hevin plays a pivotal role in the corneal wound healing.

Moesin as a key cytoskeleton regulator in corneal fibrosis

PURPOSE

: Corneal fibrosis is the third leading cause of blindness worldwide. α-Smooth muscle actin (SMA), a marker of fibrosis, is closely regulated through an intermediate group of submembrane molecules - cytoskeleton regulators. The purpose of this study was to elucidate the role of specific cytoskeleton regulators in a mouse model of corneal fibrosis.

METHODS

: A mouse model of corneal fibrosis was developed using anterior keratectomy (AK) and the topical application of transforming growth factor (TGF)-β1 (1 μg/ml). The RT² Profiler™ PCR Array for cytoskeleton regulators was used to assay changes in levels of specific members of this class of proteins. Moesin siRNA was delivered into the corneal stroma by iontophoresis in vivo. Transformation of the corneal keratocyte-to-myofibroblast in corneal fibrosis, as defined by the expression of α-SMA, was determined by Western blot.

RESULTS

: After AK and topical application of TGF-β1, moesin was the most highly upregulated gene among 84 cytoskeleton regulator genes; iontophoresing moesin siRNA into the corneal stroma reduced the expression of α-SMA to 0.22-, 0.52-, and 0.31-fold of control at postoperative (PO) day 1, 3, and 5, respectively; also, upregulation of phospho-Smad 2 induced by TGF-β1 was reduced by moesin siRNA to 0.59-, 0.56-, and 0.31-fold of control and expression of phospho-Smad 3 was reduced to 0.58-, 0.53-, and 0.47-fold of control at the same PO days.

CONCLUSIONS

: Moesin may be a potential drug target for inhibiting corneal fibrosis, and the details of moesin-related signaling pathways would be critical for understanding corneal fibrosis.

Effects of fibroblast origin and phenotype on the proliferative potential of limbal epithelial progenitor cells

The current study investigates potential differences in fibroblast phenotype across the anterior segment of the human eye with the aim to understanding factors that support the regenerative function of human limbal epithelial progenitor cells (LEPs) during wound healing. Separate cultures of fibroblasts were established from the cornea, limbus and sclera by growth in serum-supplemented medium. The resulting cultures were examined for potential differences in morphology and growth rate, as well as expression of CD34, CD45, CD90, CD141, CD271, vimentin and α-smooth muscle actin (α-sma). Finally, cultures were examined for their ability to support the growth of LEPs. While all cultures grew at a similar rate, scleral cultures often contained larger and more irregularly shaped cells which stained positive for α-sma. Western blotting confirmed a gradient of α-sma expression with lowest levels in corneal cultures. All three cultures stained positively for CD90 and vimentin, and were negative for CD34, CD45, CD141 and CD271. Only limbal or corneal irradiated fibroblasts supported the establishment of LEP cultures. While LEP colony forming efficiency and prominent expression of ABCG2, C/EBPδ and p63 was similar with either limbal or corneal fibroblasts, limbal fibroblasts supported significantly better growth. These results indicate that scleral fibroblasts have an increased capacity for myofibroblast formation which appears to negatively impact on their ability to support LEP growth. Superior growth of LEPs in the presence of limbal fibroblasts indicates a role for limbal fibroblasts in promoting the proliferation of limbal epithelium during wound healing.