Transcriptomic landscape of quiescent and proliferating human corneal stromal fibroblasts.

This study analyzed the transcriptional changes in primary human corneal stromal fibroblasts (hCSFs) grown under quiescent (serum-free) and proliferating (serum-supplemented) culture conditions to identify genes, pathways, and protein‒protein interaction networks influencing corneal repair and regeneration. Primary hCSFs were isolated from donor human corneas and maintained in serum-free or serum-laden conditions. RNA was extracted from confluent cultures using Qiagen kit and subjected to RNA sequencing (RNAseq) analysis. Differential gene expression (DGE) and pathway enrichment analyses were conducted using DESeq2 and Gene Set Enrichment Analysis (GSEA), respectively. Protein‒protein interaction (PPI) networks were created exploiting the STRING database and analyzed with Cytoscape and the cytoHubba plugin. RNA-seq revealed 5,181 genes that were significantly differentially expressed/changed among the 18,812 annotated genes (p value ˂0.05). A cutoff value of a log2-fold change of ±1.5 or greater was used to identify 674 significantly upregulated and 771 downregulated genes between quiescent and proliferating hCSFs. Pathway enrichment analysis revealed significant changes in genes linked to cell cycle regulation, inflammatory, and oxidative stress response pathways, such as E2F Targets, G2M Checkpoint, and MYC Targets, TNFA signaling via NF-kB, and oxidative phosphorylation. Protein-protein interaction network analysis highlighted critical hub genes. The FGF22, CD34, ASPN, DPT, LUM, FGF10, PDGFRB, ECM2, DCN, VEGFD, OMD, OGN, ANGPT1, CDH5, and PRELP were upregulated, whereas genes linked to cell cycle regulation and mitotic progression, such as BUB1, TTK, KIF23, KIF11, BUB1B, DLGAP5, NUSAP1, CCNA2, CCNB1, BIRC5, CDK1, KIF20A, AURKB, KIF2C, and CDCA8, were downregulated. The RNA sequences and gene count files have been submitted to the Gene Expression Omnibus (accession # GSE260476). Our study provides a comprehensive information on the transcriptional and molecular changes in hCSFs under quiescent and proliferative conditions and highlights key pathways and hub genes.

Role of aquaporins in corneal healing post chemical injury.

Aquaporins (AQPs) are transmembrane water channel proteins that regulate the movement of water through the plasma membrane in various tissues including cornea. The cornea is avascular and has specialized microcirculatory mechanisms for homeostasis. AQPs regulate corneal hydration and transparency for normal vision. Currently, there are 13 known isoforms of AQPs that can be subclassified as orthodox AQPs, aquaglyceroporins (AQGPs), or supraquaporins (SAQPs)/unorthodox AQPs. AQPs are implicated in keratocyte function, inflammation, edema, angiogenesis, microvessel proliferation, and the wound-healing process in the cornea. AQPs play an important role in wound healing by facilitating the movement of corneal stromal keratocytes by squeezing through tight stromal matrix and narrow extracellular spaces to the wound site. Deficiency of AQPs can cause reduced concentration of hepatocyte growth factor (HGF) leading to reduced epithelial proliferation, reduced/impaired keratocyte migration, reduced number of keratocytes in the injury site, delayed and abnormal wound healing process. Dysregulated AQPs cause dysfunction in osmolar homeostasis as well as wound healing mechanisms. The cornea is a transparent avascular tissue that constitutes the anterior aspect of the outer covering of the eye and aids in two-thirds of visual light refraction. Being the outermost layer of the eye, the cornea is prone to injury. Of the 13 AQP isoforms, AQP1 is expressed in the stromal keratocytes and endothelial cells, and AQP3 and AQP5 are expressed in epithelial cells in the human cornea. AQPs can facilitate wound healing through aid in cellular migration, proliferation, migration, extracellular matrix (ECM) remodeling and autophagy mechanism. Corneal wound healing post-chemical injury requires an integrative and coordinated activity of the epithelium, stromal keratocytes, endothelium, ECM, and a battery of cytokines and growth factors to restore corneal transparency. If the chemical injury is mild, the cornea will heal with normal clarity, but severe injuries can lead to partial and/or permanent loss of corneal functions. Currently, the role of AQPs in corneal wound healing is poorly understood in the context of chemical injury. This review discusses the current literature and the role of AQPs in corneal homeostasis, wound repair, and potential therapeutic target for acute and chronic corneal injuries.

Carbofuran pesticide toxicity to the eye.

Pesticide exposure to eyes is a major source of ocular morbidities in adults and children all over the world. Carbofuran (CF), N-methyl carbamate, pesticide is most widely used as an insecticide, nematicide, and acaricide in agriculture, forestry, and gardening. Contact or ingestion of carbofuran causes high morbidity and mortality in humans and pets. Pesticides are absorbed in the eye faster than other organs of the body and damage ocular tissues very quickly. Carbofuran exposure to eye causes blurred vision, pain, loss of coordination, anti-cholinesterase activities, weakness, sweating, nausea and vomiting, abdominal pain, endocrine, reproductive, and cytotoxic effects in humans depending on amount and duration of exposure. Pesticide exposure to eye injures cornea, conjunctiva, lens, retina, and optic nerve and leads to abnormal ocular movement and vision impairment. Additionally, anticholinesterase pesticides like carbofuran are known to cause salivation, lacrimation, urination, and defecation (SLUD). Carbofuran and its two major metabolites (3-hydroxycarbofuran and 3-ketocarbofuran) are reversible inhibitors of acetylcholinesterase (AChE) which regulates acetylcholine (ACh), a neurohumoral chemical that plays an important role in corneal wound healing. The corneal epithelium contains high levels of ACh whose accumulation by AChE inhibition after CF exposure overstimulates muscarinic ACh receptors (mAChRs) and nicotinic ACh receptors (nAChRs). Hyper stimulation of mAChRs in the eye causes miosis (excessive constriction of the pupil), dacryorrhea (excessive flow of tears), or chromodacryorrhea (red tears). Recent studies reported alteration of autophagy mechanism in human cornea in vitro and ex vivo post carbofuran exposure. This review describes carbofuran toxicity to the eye with special emphasis on corneal morbidities and blindness.

Mustard gas exposure instigates retinal Müller cell gliosis.

Sulfur mustard (SM) is a chemical warfare agent (CWA) that causes severe eye pain, photophobia, excessive lacrimation, corneal and ocular surface defects, and blindness. However, SM's effects on retinal cells are relatively meager. This study investigated the role of SM toxicity on Müller glial cells responsible for cellular architecture, inner blood-retinal barrier maintenance, neurotransmitter recycling, neuronal survival, and retinal homeostasis. Müller glial cells (MIO-M1) were exposed to SM analog, nitrogen mustard (NM), at varying concentrations (50-500 µM) for 3 h, 24 h, and 72 h. Müller cell gliosis was evaluated using morphological, cellular, and biochemical methods. Real-time cellular integrity and morphological evaluation were performed using the xCELLigence real-time monitoring system. Cellular viability and toxicity were measured using TUNEL and PrestoBlue assays. Müller glia hyperactivity was calculated based on glial fibrillary acidic protein (GFAP) and vimentin immunostaining. Intracellular oxidative stress was measured using DCFDA and DHE cell-based assays. Inflammatory markers and antioxidant enzyme levels were determined by quantitative real-time PCR (qRT-PCR). AO/Br and DAPI staining further evaluated DNA damage, apoptosis, necrosis, and cell death. Inflammasome-associated Caspase-1, ASC, and NLRP3 were studied to identify mechanistic insights into NM toxicity in Müller glial cells. The cellular and morphological evaluation revealed the Müller glia hyperactivity after NM exposure in a dose- and time-dependent manner. NM exposure caused significant oxidative stress and enhanced cell death at 72 h. A significant increase in antioxidant indices was observed at the lower concentrations of NM. Mechanistically, we found that NM-treated MIO-M1 cells increased caspase-1 levels that activated NLRP3 inflammasome-induced production of IL-1ß and IL-18, and elevated Gasdermin D (GSDMD) expression, a crucial component actuating pyroptosis. In conclusion, NM-induced Müller cell gliosis via increased oxidative stress results in caspase-1-dependent activation of the NLRP3 inflammasome and cell death driven primarily by pyroptosis.

Toxicological effects of ocular acrolein exposure to eyelids in rabbits in vivo.

Acrolein is a highly reactive volatile toxic chemical that injures the eyes and many organs. It has been used in wars and terrorism for wounding masses on multiple occasions and is readily accessible commercially. Our earlier studies revealed acrolein's toxicity to the cornea and witnessed damage to other ocular tissues. Eyelids play a vital role in keeping eyes mobile, moist, lubricated, and functional utilizing a range of diverse lipids produced by the Meibomian glands located in the upper and lower eyelids. This study sought to investigate acrolein's toxicity to eyelid tissues by studying the expression of inflammatory and lipid markers in rabbit eyes in vivo utilizing our reported vapor-cap model. The study was approved by the institutional animal care and use committees and followed ARVO guidelines. Twelve New Zealand White Rabbits were divided into 3 groups: Naïve (group 1), 1-min acrolein exposure (group 2), or 3-min acrolein exposure (group 3). The toxicological effects of acrolein on ocular health in live animals were monitored with regular clinical eye exams and intraocular pressure measurements and eyelid tissues post-euthanasia were subjected to H&E and Masson's trichrome histology and qRT-PCR analysis. Clinical eye examinations witnessed severely swollen eyelids, abnormal ocular discharge, chemosis, and elevated intraocular pressure (p < 0.001) in acrolein-exposed eyes. Histological studies supported clinical findings and exhibited noticeable changes in eyelid tissue morphology. Gene expression studies exhibited significantly increased expression of inflammatory and lipid mediators (LOX, PAF, Cox-2, and LTB4; p < 0.001) in acrolein-exposed eyelid tissues compared to naïve eyelid tissues. The results suggest that acrolein exposure to the eyes causes acute damage to eyelids by altering inflammatory and lipid mediators in vivo.

Differential gene expression and protein-protein interaction network profiling of sulfur mustard-exposed rabbit corneas employing RNA-seq data and bioinformatics tools.

Sulfur mustard (SM) ocular exposure severely damages the cornea and causes vision impairment. At present, no specific therapy exists to mitigate SM-induced corneal injury and vision loss. This study performed transcriptome profiling of naïve, SM-damaged, and SM-undamaged rabbit corneas using RNA-seq analysis and bioinformatic tools to gain a better mechanistic understanding and develop SM-specific medical countermeasures. The mRNA profiles of rabbit corneas 4 weeks post SM vapor exposure were generated using Illumina-NextSeq deep sequencing (Gene Expression Omnibus accession # GSE127708). The RNA sequences of naïve (n = 4), SM-damaged (n = 5), and SM-undamaged (n = 5) corneas were subjected to differential expression (DE) analysis after quality control profiling with FastQC. DE analysis was performed using HISAT2, StringTie, and DESeq2. The log2(FC)±2 and adjusted p˂0.05 were chosen to identify the most relevant genes. A total of 5930 differentially expressed genes (DEGs) (upregulated: 3196, downregulated: 2734) were found in SM-damaged corneas compared to naïve corneas, whereas SM-undamaged corneas showed 1884 DEGs (upregulated: 1029, downregulated: 855) compared to naïve corneas. DE profiling of SM-damaged corneas to SM-undamaged corneas revealed 985 genes (upregulated: 308, downregulated: 677). The DE profiles were subsequently subjected to signaling pathway enrichment, and protein‒protein interactions (PPIs) were analyzed. Pathway enrichment was performed for the genes associated with cellular apoptosis, death, adhesion, migration, differentiation, proliferation, extracellular matrix, and tumor necrosis factor production. To identify novel targets, we narrowed the pathway analysis to upregulated and downregulated genes associated with cell proliferation and differentiation, and PPI networks were developed. Furthermore, protein targets associated with cell differentiation and proliferation that may play vital roles in corneal fibrosis and wound healing post SM injury were identified.

Characterization of C-X-C chemokine receptor type 5 in the cornea and role in the inflammatory response after corneal injury.

C-X-C chemokine receptor type 5 (CXCR5) regulates inflammatory responses in ocular and non-ocular tissues. However, its expression and role in the cornea are still unknown. Here, we report the expression of CXCR5 in human cornea in vitro and mouse corneas in vivo, and its functional role in corneal inflammation using C57BL/6J wild-type (CXCR5+/+) and CXCR5-deficient (CXCR5-/-) mice, topical alkali injury, clinical eye imaging, histology, immunofluorescence, PCR, qRT-PCR, and western blotting. Human corneal epithelial cells, stromal fibroblasts, and endothelial cells demonstrated CXCR5 mRNA and protein expression in PCR, and Western blot analyses, respectively. To study the functional role of CXCR5 in vivo, mice were divided into four groups: Group-1 (CXCR5+/+ alkali injured cornea; n = 30), Group-2 (CXCR5-/- alkali injured cornea; n = 30), Group-3 (CXCR5+/+ naïve cornea; n = 30), and Group-4 (CXCR5-/- naïve cornea; n = 30). Only one eye was wounded with alkali. Clinical corneal evaluation and imaging were performed before and after injury. Mice were euthanized 4 h, 3 days, or 7 days after injury, eyes were excised and used for histology, immunofluorescence, and qRT-PCR. In clinical eye examinations, CXCR5-/- mouse corneas showed ocular health akin to the naïve corneas. Alkali injured CXCR5+/+ mouse corneas showed significantly increased mRNA (p < 0.001) and protein (p < 0.01 or p < 0.0001) levels of the CXCR5 compared to the naïve corneas. Likewise, alkali injured CXCR5-/- mouse corneas showed remarkably amplified inflammation in clinical eye exams in live animals. The histological and molecular analyses of these corneas post euthanasia exhibited markedly augmented inflammatory cells in H&E staining and significant CD11b + cells in immunofluorescence (p < 0.01 or < 0.05); and tumor necrosis factor-alpha (TNFα; p < 0.05), cyclooxygenase 2 (COX-2; p < 0.0001), interleukin (IL)-1ß (p < 0.0001), and IL-6 (p < 0.0001 or < 0.01) mRNA expression compared to the CXCR5+/+ mouse corneas. Interestingly, CXCR5-/- alkali injured corneas also showed altered mRNA expression of fibrotic alpha smooth muscle actin (α-SMA; p > 0.05) and angiogenic vascular endothelial growth factor (VEGF; p < 0.01) compared to the CXCR5+/+ alkali injured corneas. In summary, the CXCR5 gene is expressed in all three major layers of the cornea and appears to influence corneal inflammatory and repair events post-injury in vivo. More studies are warranted to tease the mechanistic role of CXCR5 in corneal inflammation and wound healing.

Corneal fibrosis abrogation by a localized AAV-mediated inhibitor of differentiation 3 (Id3) gene therapy in rabbit eyes in vivo.

Previously we found that inhibitor of differentiation 3 (Id3) gene, a transcriptional repressor, efficiently inhibits corneal keratocyte differentiation to myofibroblasts in vitro. This study evaluated the potential of adeno-associated virus 5 (AAV5)-mediated Id3 gene therapy to treat corneal scarring using an established rabbit in vivo disease model. Corneal scarring/fibrosis in rabbit eyes was induced by alkali trauma, and 24 h thereafter corneas were administered with either balanced salt solution AAV5-naked vector, or AAV5-Id3 vector (n = 6/group) via an optimized reported method. Therapeutic effects of AAV5-Id3 gene therapy on corneal pathology and ocular health were evaluated with clinical, histological, and molecular techniques. Localized AAV5-Id3 gene therapy significantly inhibited corneal fibrosis/haze clinically from 2.7 to 0.7 on the Fantes scale in live animals (AAV5-naked versus AAV5-Id3; p < 0.001). Furthermore, AAV5-Id3 treatment significantly reduced profibrotic gene mRNA levels: α-smooth muscle actin (α-SMA) (2.8-fold; p < 0.001), fibronectin (3.2-fold; p < 0.001), collagen I (0.8-fold; p < 0.001), and collagen III (1.4-fold; p < 0.001), as well as protein levels of α-SMA (23.8%; p < 0.001) and collagens (1.8-fold; p < 0.001). The anti-fibrotic activity of AAV5-Id3 is attributed to reduced myofibroblast formation by disrupting the binding of E-box proteins to the promoter of α-SMA, a transforming growth factor-ß signaling downstream target gene. In conclusion, these results indicate that localized AAV5-Id3 delivery in stroma caused no clinically relevant ocular symptoms or corneal cellular toxicity in the rabbit eyes.

Evaluation of CRISPR/Cas9 mediated TGIF gene editing to inhibit corneal fibrosis in vitro.

Corneal wound healing is influenced by many factors including transcriptional co-repressors and co-activators. Interactions of co-activators and co-repressors with Smads influence mechanistic loop facilitating transcription of alpha-smooth muscle actin (α-SMA), a key profibrotic gene, in corneal repair. The role of a transcriptional repressor, 5'TG3'-interacting factor (TGIF), in the regulation of α-SMA and myofibroblast formation in the cornea was shown previously by our group. This study tested a hypothesis if TGIF1 gene editing via CRISPR/Cas9 can ease myofibroblast formation in the cornea using an in vitro model. Primary human corneal stromal fibroblasts (hCSFs) generated from donor corneas received gene-editing plasmid facilitating loss (CRISPR/Cas9 knockout) or gain (CRISPR activation) of TGIF function by UltraCruz transfection reagent. Phase-contrast microscopy, immunoblotting, immunocytochemistry and quantitative polymerase chain reaction (qPCR) were used to measure levels of myofibroblast profibrotic genes (α-SMA, fibronectin, Collagen-I, and Collagen-IV) in hCSFs lacking or overexpressing TGIF1 after growing them in± transforming growth factor beta1 (TGF-ß1) under serum-free conditions. The CRISPR-assisted TGIF1 activation (gain of function) in hCSFs demonstrated significantly decreased myofibroblast formation and messenger ribonucleic acid (mRNA) and protein levels of profibrotic genes. Conversely, CRISPR/Cas9-assisted TGIF knockdown (loss of function) in hCSFs demonstrated no significant change in the levels of myofibroblast formation or profibrotic genes under similar conditions. These results suggest that TGIF gene-editing approach can be employed to modulate the transcriptional activity of α-SMA in controlling pathological and promoting physiological wound healing in an injured cornea.

Time-dependent in situ structural and cellular aberrations in rabbit cornea in vivo after mustard gas exposure.

An array of corneal pathologies collectively called mustard gas keratopathy (MGK) resulting from ocular exposure to sulfur mustard (SM) gas are the most prevalent chemical warfare injury. MGK involves chronic ocular discomfort that results in vision impairment. The etiology of MGK remains unclear and poorly understood primarily due to a lack of scientific data regarding structural and cellular changes in different layers of the cornea altered by mustard vapor exposure in vivo. The goals of this study were to (a) characterize time-dependent changes in different layers of corneal epithelium, stroma, and endothelium in live animals in situ by employing state-of-the-art multimodal clinical ophthalmic imaging techniques and (b) determine if SM-induced acute changes in corneal cells could be rescued by a topical eye drop (TED) treatment using in an established rabbit in vivo model. Forty-five New Zealand White Rabbit eyes were divided into four groups (Naïve, TED, SM, and SM + TED). Only one eye was exposed to SM (200 mg-min/m3 for 8 min), and each group had three time points with six eyes each (Table-1). TED was topically applied twice a day for seven days. Clinical eye examinations and imaging were performed in live rabbits with stereo, Slit-lamp, HRT-RCM3, and Spectralis microscopy system. Fantes grading, fluorescein staining, Schirmer's tests, and applanation tonometry were conducted to measure corneal haze, ocular surface aberrations, tears, and intraocular pressure respectively. H&E and PSR staining were used for histopathological cellular changes in the cornea. In vivo confocal and OCT imaging revealed significant changes in structural and morphological appearance of corneal epithelium, stroma, and endothelium in vivo in SM-exposed rabbit corneas in a time-dependent manner compared to naïve cornea. Also, SM-exposed eyes showed loss of corneal transparency characterized by increased stromal thickness and light-scattering myofibroblasts or activated keratocytes, representing haze formation in the cornea. Neither naive nor TED-alone treated eyes showed any structural, cellular, and functional abnormalities. Topical TED treatment significantly reduced SM-induced abnormalities in primary corneal layers. We conclude that structural and cellular changes in primary corneal layers are early pathological events contributing to MGK in vivo, and efficient targeting of them with suitable agents has the potential to mitigate SM ocular injury.

Collagen matrix perturbations in corneal stroma of Ossabaw mini pigs with type 2 diabetes.

Purpose: Diabetes mellitus (DM) is a metabolic disorder that affects over 450 million people worldwide. DM is characterized by hyperglycemia, causing severe systemic damage to the heart, kidneys, skin, vasculature, nerves, and eye. Type 2 diabetes (T2DM) constitutes 90% of clinical cases and is the most common cause of blindness in working adults. Also, about 70% of T2DM patients show corneal complications including delayed wound healing, often described as diabetic keratopathy (DK). Despite the increasing severity of DM, the research on DK is bleak. This study investigated cellular morphology and collagen matrix alterations of the diabetic and non-diabetic corneas collected from Ossabaw mini pigs, a T2DM animal model with a "thrifty genotype." Methods: Pig corneas were collected from six-month-old Ossabaw miniature pigs fed on a western diet (WD) for ten weeks. The tissues were processed for immunohistochemistry and analyzed using hematoxylin and eosin staining, Mason Trichrome staining, Picrosirus Red staining, Collage I staining, and TUNEL assay. mRNA was prepared to quantify fibrotic gene expression using quantitative reverse-transcriptase PCR (qRT-PCR). Transmission electron microscopy (TEM) was performed to evaluate stromal fibril arrangements to compare collagen dynamics in WD vs. standard diet (SD) fed Ossabaw pig corneas. Results: Ossabaw mini pigs fed on a WD for 10 weeks exhibit classic symptoms of metabolic syndrome and hyperglycemia seen in T2DM patients. We observed significant disarray in cornea stromal collagen matrix in Ossabaw mini pigs fed on WD compared to the age-matched mini pigs fed on a standard chow diet using Masson Trichome and Picrosirius Red staining. Furthermore, ultrastructure evaluation using TEM showed alterations in stromal collagen fibril size and organization in diabetic corneas compared to healthy age-matched corneas. These changes were accompanied by significantly decreased levels of Collagen IV and increased expression of matrix metallopeptidase 9 in WD-fed pigs. Conclusions: This pilot study indicates that Ossabaw mini pigs fed on WD showed collagen disarray and altered gene expression involved in wound healing, suggesting that corneal stromal collagens are vulnerable to diabetic conditions.

Novel insights into gene therapy in the cornea.

Corneal disease remains a leading cause of impaired vision world-wide, and advancements in gene therapy continue to develop with promising success to prevent, treat and cure blindness. Ideally, gene therapy requires a vector and gene delivery method that targets treatment of specific cells or tissues and results in a safe and non-immunogenic response. The cornea is a model tissue for gene therapy due to its ease of clinician access and immune-privileged state. Improvements in the past 5-10 years have begun to revolutionize the approach to gene therapy in the cornea with a focus on adeno-associated virus and nanoparticle delivery of single and combination gene therapies. In addition, the potential applications of gene editing (zinc finger nucleases [ZNFs], transcription activator-like effector nucleases [TALENs], Clustered Regularly Interspaced Short Palindromic Repeats/Associated Systems [CRISPR/Cas9]) are rapidly expanding. This review focuses on recent developments in gene therapy for corneal diseases, including promising multiple gene therapy, while outlining a practical approach to the development of such therapies and potential impediments to successful delivery of genes to the cornea.

Role of inhibitor of differentiation 3 gene in cellular differentiation of human corneal stromal fibroblasts.

Purpose: Inhibitor of differentiation (Id) proteins are helix-loop-helix (HLH) transcriptional repressors that modulate a range of developmental and cellular processes, including cell differentiation and cell cycle mobilization. The inhibitor of differentiation 3 (Id3) gene, a member of the Id gene family, governs the expression and progression of transforming growth factor beta (TGFß)-mediated cell differentiation. In the face of mechanical, chemical, or surgical corneal insults, corneal keratocytes differentiate into myofibroblasts for wound repair. Excessive development or persistence or both of myofibroblasts after wound repair results in corneal haze that compromises corneal clarity and visual function. The objective of this study was to investigate whether Id3 overexpression in human corneal stromal fibroblasts governs TGFß-driven cellular differentiation and inhibits keratocyte to myofibroblast transformation. Methods: Primary human corneal stromal fibroblast (h-CSF) cultures were generated from donor human corneas. Human corneal myofibroblasts (h-CMFs) were produced by growing h-CSF in the presence of TGFß1 under serum-free conditions. The Id3 gene was cloned into a mammalian expression vector (pcDNA3 mCherry LIC cloning vector), and the nucleotide sequence of the vector constructs was confirmed with sequencing as well as through restriction enzyme analysis. The Id3 mammalian overexpression vector was introduced into h-CSFs using a lipofectamine transfection kit. The expression of Id3 in selected clones was characterized with quantitative real-time PCR (qRT-PCR), immunocytochemistry, and western blotting. Phase contrast microscopy and trypan blue exclusion assays were used to evaluate the effects of the transfer of the Id3 gene on the hCSF phenotype and viability, respectively. To analyze the inhibitory effects of the Id3 gene transfer on TGFß-induced formation of h-CMFs, expression of the mRNA and protein of the myofibroblast marker alpha smooth muscle actin (α-SMA) was examined with qRT-PCR, western blotting, and immunocytochemistry. Student t test, analysis of variance (ANOVA), and Bonferroni adjustment for repeated measures were used for statistical analysis. Results: The results indicate that Id3 overexpression does not alter the cellular phenotype or viability of h-CSFs. Overexpression of the Id3 gene in h-CSF cells grown in the presence of TGFß1 under serum-free conditions showed a statistically significant decrease (76.3±4.3%) in α-SMA expression (p<0.01) compared to the naked-vector transfected or non-transfected h-CSF cells. Id3-transfected, naked-vector transfected, and non-transfected h-CSF cells grown in the absence of TGFß1 showed the expected low expression of α-SMA (0-5%). Furthermore, Id3 overexpression statistically significantly decreased TGFß-induced mRNA levels of profibrogenic genes such as fibronectin, collagen type I, and collagen type IV (1.80±0.26-, 1.70±0.35- and 1.70±0.36-fold, respectively; p<0.05) that a play role in stromal matrix modulation and corneal wound healing. Results of the protein analysis with western blotting indicated that Id3 overexpression in h-CSF cells effectively slows TGFß-driven differentiation and formation of h-CMFs. Results for subsequent overexpression studies showed that this process occurs through the regulation of E2A, a TATA box protein. Conclusions: Id3 regulates TGFß-driven differentiation of h-CSFs and formation of h-CMFs in vitro. Targeted Id3 gene delivery has potential to treat corneal fibrosis and reestablish corneal clarity in vivo.

Role of 5'TG3'-interacting factors (TGIFs) in Vorinostat (HDAC inhibitor)-mediated Corneal Fibrosis Inhibition.

PURPOSE: We have previously reported that vorinostat, an FDA-approved, clinically used histone deacetylase (HDAC) inhibitor, attenuates corneal fibrosis in vivo in rabbits by blocking transforming growth factor ß (TGFß). The 5'TG3'-interacting factors (TGIFs) are transcriptional repressors of TGFß1 signaling via the Smad pathway. The present study was designed to explore the expression of TGIFs in human corneal fibroblasts and to investigate their role in mediating the antifibrotic effect of vorinostat. METHODS: Human corneal fibroblast cultures were generated from donor corneas. RNA isolation, cDNA preparation, and PCR were performed to detect the presence of TGIF1 and TGIF2 transcripts. The cultures were exposed to vorinostat (2.5 µM) to test its effect on TGIF mRNA and protein levels using qPCR and immunoblotting. Myofibroblast formation was induced with TGFß1 (5 ng/ml) treatment under serum-free conditions. The changes in fibrosis parameters were quantified by measuring fibrosis marker α-smooth muscle actin (αSMA) mRNA and protein levels with qPCR, immunostaining, and immunoblotting. Smad2/3/4 and TGIF knockdowns were performed using pre-validated RNAi/siRNAs and a commercially available transfection reagent. RESULTS: Human corneal fibroblasts showed the expression of TGIF1 and TGIF2. Vorinostat (2.5 µM) caused a 2.8-3.3-fold increase in TGIF1 and TGIF2 mRNA levels and a 1.4-1.8-fold increase in TGIF1 and TGIF2 protein levels. Vorinostat treatment also caused a significant increase in acetylhistone H3 and acetylhistone H4. Vorinostat-induced increases in TGIF1 and TGIF2 were accompanied by a concurrent decrease in corneal fibrosis, as indicated by a decrease in αSMA mRNA by 83±7.7% and protein levels by 97±5%. The RNAi-mediated knockdown of Smad2, Smad3, and Smad4 markedly attenuated TGFß1-evoked transdifferentiation of fibroblasts to myofibroblasts. The siRNA-mediated knockdown of TGIF1 and TGIF2 neutralized vorinostat-evoked decreases in αSMA mRNA by 31%-45% and protein levels by 12%-23%. CONCLUSIONS: Human corneal fibroblasts demonstrate the expression of TGIF1 and TGIF2 transcription factors. These transcriptional repressors are critical, at least partially, in mediating the antifibrotic effect of vorinostat in the cornea.

RNA-Seq Analysis Unraveling Novel Genes and Pathways Influencing Corneal Wound Healing.

Purpose: Transdifferentiation of corneal fibroblasts to myofibroblasts in the stroma is a central mechanistic event in corneal wound healing. This study sought to characterize genes and pathways influencing transdifferentiation of human corneal fibroblasts (hCSFs) to human corneal myofibroblasts (hCMFs) using RNA sequencing (RNA-seq) to develop comprehensive mechanistic information and identify newer targets for corneal fibrosis management. Methods: Primary hCSFs were derived from donor human corneas. hCMFs were generated by treating primary hCSFs with transforming growth factor ß1 (TGFß1; 5 ng/mL) for 72 hours under serum-free conditions. RNA was extracted using the RNeasy Plus Mini Kit and subjected to RNA-seq analysis after quality control testing. Differential gene expression, pathway enrichment, and protein-protein network analyses were performed using DESeq2, GSEA/PANTHER/Reactome, and Cytoscape/cytoHubba, respectively. Results: RNA-seq analysis of hCMFs and hCSFs identified 3843 differentially expressed genes and transcripts (adjusted P < 0.05). The log(fold change) ≥ ±1.5 filter showed 816 upregulated and 739 downregulated genes between two cell types. Pathway enrichment analysis showed the highest normalized enrichment score for epithelial-to-mesenchymal transition (5.569), followed by mTORC1 signaling (2.949), angiogenesis (2.176), and TGFß signaling (2.008). Protein-protein interaction network analysis identified the top 20 nodes influencing corneal myofibroblast development. The expression of a novel MXRA5 in corneal stroma and its association with corneal fibrosis was verified by real-time quantitative reverse transcription PCR and immunofluorescence. RNA-seq and gene count files were submitted to the NCBI Gene Expression Omnibus (GSE260476). Conclusions: This study identified several novel genes involved in myofibroblast development, offering potential targets for developing newer therapeutic strategies for corneal fibrosis.

Tissue-targeted and localized AAV5-DCN and AAV5-PEDF combination gene therapy abrogates corneal fibrosis and concurrent neovascularization in rabbit eyes in vivo.

PURPOSE: Corneal fibrosis and neovascularization (CNV) after ocular trauma impairs vision. This study tested therapeutic potential of tissue-targeted adeno-associated virus5 (AAV5) mediated decorin (DCN) and pigment epithelium-derived factor (PEDF) combination genes in vivo. METHODS: Corneal fibrosis and CNV were induced in New Zealand White rabbits via chemical trauma. Gene therapy in stroma was delivered 30-min after chemical-trauma via topical AAV5-DCN and AAV5-PEDF application using a cloning cylinder. Clinical eye examinations and multimodal imaging in live rabbits were performed periodically and corneal tissues were collected 9-day and 15-day post euthanasia. Histological, cellular, and molecular and apoptosis assays were used for efficacy, tolerability, and mechanistic studies. RESULTS: The AAV5-DCN and AAV5-PEDF combination gene therapy significantly reduced corneal fibrosis (p < 0.01 or p < 0.001) and CNV (p < 0.001) in therapy-given (chemical-trauma and AAV5-DCN + AAV5-PEDF) rabbit eyes compared to the no-therapy given eyes (chemical-trauma and AAV5-naked vector). Histopathological analyses demonstrated significantly reduced fibrotic α-smooth muscle actin and endothelial lectin expression in therapy-given corneas compared to no-therapy corneas on day-9 (p < 0.001) and day-15 (p < 0.001). Further, therapy-given corneas showed significantly increased Fas-ligand mRNA levels (p < 0.001) and apoptotic cell death in neovessels (p < 0.001) compared to no-therapy corneas. AAV5 delivered 2.69 × 107 copies of DCN and 2.31 × 107 copies of PEDF genes per µg of DNA. AAV5 vector and delivered DCN and PEDF genes found tolerable to the rabbit eyes and caused no significant toxicity to the cornea. CONCLUSION: The combination AAV5-DCN and AAV5-PEDF topical gene therapy effectively reduces corneal fibrosis and CNV with high tolerability in vivo in rabbits. Additional studies are warranted.

Corneal gene therapy: Structural and mechanistic understanding.

Cornea, a dome-shaped and transparent front part of the eye, affords 2/3rd refraction and barrier functions. Globally, corneal diseases are the leading cause of vision impairment. Loss of corneal function including opacification involve the complex crosstalk and perturbation between a variety of cytokines, chemokines and growth factors generated by corneal keratocytes, epithelial cells, lacrimal tissues, nerves, and immune cells. Conventional small-molecule drugs can treat mild-to-moderate traumatic corneal pathology but requires frequent application and often fails to treat severe pathologies. The corneal transplant surgery is a standard of care to restore vision in patients. However, declining availability and rising demand of donor corneas are major concerns to maintain ophthalmic care. Thus, the development of efficient and safe nonsurgical methods to cure corneal disorders and restore vision in vivo is highly desired. Gene-based therapy has huge potential to cure corneal blindness. To achieve a nonimmunogenic, safe and sustained therapeutic response, the selection of a relevant genes, gene editing methods and suitable delivery vectors are vital. This article describes corneal structural and functional features, mechanistic understanding of gene therapy vectors, gene editing methods, gene delivery tools, and status of gene therapy for treating corneal disorders, diseases, and genetic dystrophies.

Novel Therapies for the Prevention of Fibrosis in Glaucoma Filtration Surgery.

Conjunctival fibrosis remains the major impediment to the success of glaucoma filtration surgery. Anti-metabolites remain the gold standard for mitigating post-surgical fibrosis, but they are associated with high complication rates and surgical failure rates. Establishing a more targeted approach to attenuate conjunctival fibrosis may revolutionize the surgical approach to glaucoma. A new strategy is needed to prevent progressive tissue remodeling and formation of a fibrotic scar, subsequently increasing surgical success and reducing the prevalence of glaucoma-related vision loss. Advancements in our understanding of molecular signaling and biomechanical cues in the conjunctival tissue architecture are broadening the horizon for new therapies and biomaterials for the mitigation of fibrosis. This review aims to highlight the strategies and current state of promising future approaches for targeting fibrosis in glaucoma filtration surgery.

Mustard Gas Exposure Actuates SMAD2/3 Signaling to Promote Myofibroblast Generation in the Cornea.

Sulfur mustard gas (SM) is a vesicating and alkylating agent used as a chemical weapon in many mass-casualty incidents since World War I. Ocular injuries were reported in >90% of exposed victims. The mechanisms underlying SM-induced blindness remain elusive. This study tested the hypothesis that SM-induced corneal fibrosis occurs due to the generation of myofibroblasts from resident fibroblasts via the SMAD2/3 signaling pathway in rabbit eyes in vivo and primary human corneal fibroblasts (hCSFs) isolated from donor corneas in vitro. Fifty-four New Zealand White Rabbits were divided into three groups (Naïve, Vehicle, SM-Vapor treated). The SM-Vapor group was exposed to SM at 200 mg-min/m3 for 8 min at the MRI Global facility. Rabbit corneas were collected on day 3, day 7, and day 14 for immunohistochemistry, RNA, and protein lysates. SM caused a significant increase in SMAD2/3, pSMAD, and ɑSMA expression on day 3, day 7, and day 14 in rabbit corneas. For mechanistic studies, hCSFs were treated with nitrogen mustard (NM) or NM + SIS3 (SMAD3-specific inhibitor) and collected at 30 m, 8 h, 24 h, 48 h, and 72 h. NM significantly increased TGFß, pSMAD3, and SMAD2/3 levels. On the contrary, inhibition of SMAD2/3 signaling by SIS3 treatment significantly reduced SMAD2/3, pSMAD3, and ɑSMA expression in hCSFs. We conclude that SMAD2/3 signaling appears to play a vital role in myofibroblast formation in the cornea following mustard gas exposure.