MicroRNAs in the cornea: Role and implications for treatment of corneal neovascularization

Crosstalk among miR-29, α-SMA, and TGFβ1/β3 in melatonin-induced exosome (Mel-prExo) treated human limbal mesenchymal stem cells (hLMSCs): An insight into scarless healing of the cornea

Inflammatory mediators that infiltrate the corneal stroma after corneal infections, trauma or refractive surgery can trigger the transformation of corneal keratocytes into myofibroblasts, resulting in highly irregular collagen deposition and subsequently corneal scarring. Mesenchymal stem cells (MSCs) can be used as therapeutic agents to regenerate corneal and conjunctival tissue damage, regulate inflammation, and reduce the development of limbal stem cell failure. The use of MSC-derived exosomes as a cell-free therapeutic vector is a novel therapeutic approach. This study aimed to assess the effect of exosomes obtained from melatonin (Mel)-treated human limbal mesenchymal stem cells (hLMSCs) on naïve hLMSCs and to determine their influence on the antifibrotic and pro-regenerative pathways involved in corneal scarring. hLMSCs were treated with varying concentrations of Mel, followed by isolation and characterization of the procured exosomes (Mel-prExos). These exosomes were added to the cell culture media of naïve hLMSCs to examine their antifibrotic and pro-regenerative effects. The expression of miR-155, miR-29, TGFβ1, TGFβ3, PPARγ, and α-SMA miRNAs and genes were compared between Mel-treated hLMSCs and Mel-prExo-treated hLMSCs by using real-time PCR. We found that at 1 μM Mel and in the presence of Mel-prExos, TGFβ1 was expressed 0.001-fold, while TGFβ3 was expressed 0.6-fold. miR-29 expression was increased 38-fold in the control-Exo group compared to that in the control group. Changes in TGFβ1/β3 and α-SMA expression are associated with miR-29 and miR-155. This approach could prove beneficial for ocular surface tissue engineering applications.

The application of high-throughput sequencing technology in corneal diseases

High-throughput sequencing technology, also known as next-generation sequencing technology, can explore new biomarkers and specific gene mutations. It has a pivotal role in promoting the gene research, which can limit the detection area, lessen the time needed for sequencing. Also, it can quickly screen out the suspected pathogenic genes of patients, gain the necessary genetic data, and provide the basis for clinical diagnosis and genetic counseling. In the research of corneal diseases, through the DNA sequencing of patients' diseased cells, it can provide a deeper understanding of corneal diseases and improve the diagnosis, classification and treatment alternatives of various corneal diseases. This article will introduce the application progress of high-throughput sequencing technology in corneal diseases, which will help to understand the application of this technology in various corneal diseases.

Dexamethasone and MicroRNA-204 Inhibit Corneal Neovascularization

INTRODUCTION

This was an in vivo animal study designed to investigate the interaction between dexamethasone (Dex) and microRNA-204 (miR-204) in a mouse alkali burn-induced corneal neovascularization (CNV) model. The function of miR-204 was then investigated in human mammary epithelial cells (HMECs) in vitro.

MATERIALS AND METHODS

The CNV model was induced by corneal alkali burn in BLAB/c mice. The mice were randomly divided into five groups: normal control (Ctrl), alkali burn-induced corneal injury (Alkali), alkali burn + Dex (Dex), alkali burn + negative control (NTC), and alkali burn + miR-204 agomir (miR-204). Subconjunctival injection of NTC, Dex, or miR-204 agomir was conducted at 0, 3, and 6 days, respectively, after alkali burn. The corneas were collected at day 7 after injury, and the CNV area was observed using immunofluorescence staining. The expression of miR-204 was analyzed with quantitative real time (qRT)-PCR. In HMECs, exogenous miR-204 agomir or antagomir was used to strengthen or inhibit the expression of miR-204. Migration assays and tube formation studies were conducted to evaluate the function of miR-204 on HMECs.

RESULTS

At 7 days post-alkali burn, CNV grew aggressively into the cornea. MicroRNA-204 expression was reduced in the Alkali group in contrast with the Ctrl group (P = .003). However, miR-204 was upregulated in the Dex group (vs. alkali group, P = .008). The CNV areas in the NTC and miR-204 groups were 59.30 ± 8.32% and 25.60 ± 2.30%, respectively (P = .002). In vitro, miR-204 agomir showed obvious inhibition on HMEC migration in contrast with NTC (P = .033) and miR-204 antagomir (P = .017). Compared with NTC, miR-204 agomir attenuated tube formation, while miR-204 antagomir accelerated HMEC tube formation (P < .05).

CONCLUSION

The role of Dex in attenuating CNV may be partly attributed to miR-204. MiR-204 may be a potential therapeutic target in alkali burn-induced CNV.

Rational design and synthesis of lumican stapled peptides for promoting corneal wound healing

PURPOSE

Lumican is a major extracellular matrix (ECM) component in the cornea that is upregulated after injury and promotes corneal wound healing. We have recently shown that peptides designed based on the 13 C-terminal amino acids of lumican (LumC13 and LumC13C-A) are able to recapitulate the effects of lumican on promoting corneal wound healing. Herein we used computational chemistry to develop peptide mimetics derived from LumC13C-A with increased stability and half-life that are biologically active and non-toxic, thereby promoting corneal wound healing with increased pharmacological potential.

METHODS

Different peptides staples were rationalized using LumC13C-A sequence by computational chemistry, docked to TGFβRI and the interface binding energies compared. Lowest scoring peptides were synthesized, and the toxicity of peptides tested using CCK8-based cell viability assay. The efficacy of the stapled peptides at promoting corneal wound healing was tested using a proliferation assay, an in vitro scratch assay using human corneal epithelial cells and an in vivo murine corneal debridement wound healing model.

RESULTS

Binding free energies were calculated using MMGBSA algorithm, and peptides LumC13C and LumC13S5 displayed superior binding to ALK5 compared to the non-stapled peptide LumC13C-A. The presence of the hydrocarbon staple in LumC13C enhances the stability of the α-helical conformation, thereby facilitating more optimal interactions with the ALK5 receptor. The stapled peptides do not present cytotoxic effects on human corneal epithelial cells at a 300 nM concentration. Similar to lumican and LumC13C-A, both C13C and LumC13S5 significantly promote corneal wound healing both in vitro and in vivo.

CONCLUSIONS

Highly stable and non-toxic stapled peptides designed based on LumC13, significantly promote corneal wound healing. As a proof of principle, our data shows that more stable and pharmacologically relevant peptides can be designed based on endogenous peptide sequences for treating various corneal pathologies.

Effect of topical motesanib in experimental corneal neovascularization model

PURPOSE

This study aimed to compare the efficacy of topical bevacizumab and motesanib in an experimental corneal neovascularization model, and find the most effective motesanib dose.

MATERIALS AND METHODS

In experiments, 42 Wistar Albino rats were randomly divided into six groups (n = 7). Corneal cauterization was applied to all groups except the group 1. Group 1 did not receive any treatment. Topical dimethylsulfoxide was applied to sham group three times a day(tid). Topical bevacizumab drops (5 mg/ml) were applied to Group 3 tid. Topical motesanib drops with a dose of 2.5, 5, and 7.5 mg/ml were respectively applied in Groups 4, 5, and 6 tid. On the 8th day, corneal photographs of all rats were taken under general anesthesia, and the percentage of corneal neovascular area was calculated. VEGF-A mRNA, VEGFR-2 mRNA, miRNA-21, miRNA-27a, miRNA-31, miRNA-126, miRNA-184, and miRNA-204 were evaluated by the qRT-PCR method in corneas taken after decapitation.

RESULTS

The percentage of corneal neovascularization areas and VEGF-A mRNA expression levels were decreased in all treatment groups compared to group 2 (p < 0.05). VEGFR-2 mRNA levels were found to be statistically significantly decreased in groups 4 and 6 compared to group 2 (p < 0.05). Statistically significant changes were detected in the expression levels of only miRNA-126 among all miRNAs.

CONCLUSION

Motesanib with a dose of 7.5 mg/ml statistically significantly suppressed the VEGFR-2 mRNA level compared with other treatment doses and may be more effective than bevacizumab. Further, miRNA-126 can be used as a proangiogenic marker.

Congenital aniridia beyond black eyes: From phenotype and novel genetic mechanisms to innovative therapeutic approaches

Congenital PAX6-aniridia, initially characterized by the absence of the iris, has progressively been shown to be associated with other developmental ocular abnormalities and systemic features making congenital aniridia a complex syndromic disorder rather than a simple isolated disease of the iris. Moreover, foveal hypoplasia is now recognized as a more frequent feature than complete iris hypoplasia and a major visual prognosis determinant, reversing the classical clinical picture of this disease. Conversely, iris malformation is also a feature of various anterior segment dysgenesis disorders caused by PAX6-related developmental genes, adding a level of genetic complexity for accurate molecular diagnosis of aniridia. Therefore, the clinical recognition and differential genetic diagnosis of PAX6-related aniridia has been revealed to be much more challenging than initially thought, and still remains under-investigated. Here, we update specific clinical features of aniridia, with emphasis on their genotype correlations, as well as provide new knowledge regarding the PAX6 gene and its mutational spectrum, and highlight the beneficial utility of clinically implementing targeted Next-Generation Sequencing combined with Whole-Genome Sequencing to increase the genetic diagnostic yield of aniridia. We also present new molecular mechanisms underlying aniridia and aniridia-like phenotypes. Finally, we discuss the appropriate medical and surgical management of aniridic eyes, as well as innovative therapeutic options. Altogether, these combined clinical-genetic approaches will help to accelerate time to diagnosis, provide better determination of the disease prognosis and management, and confirm eligibility for future clinical trials or genetic-specific therapies.

Nanotechnology Lighting the Way for Gene Therapy in Ophthalmopathy: From Opportunities toward Applications

Hereditary ophthalmopathy is a well-described threat to human visual health affecting millions of people. Gene therapy for ophthalmopathy has received widespread attention with the increasing understanding of pathogenic genes. Effective and safe delivery of accurate nucleic acid drugs (NADs) is the core of gene therapy. Efficient nanodelivery and nanomodification technologies, appropriate targeted genes, and the choice of drug injection methods are the guiding lights of gene therapy. Compared with traditional drugs, NADs can specifically change the expression of specific genes or restore the normal function of mutant genes. Nanodelivery carriers can improve targeting and nanomodification can improve the stability of NADs. Therefore, NADs, which can fundamentally solve pathogeny, hold great promise in the treatment of ophthalmopathy. This paper reviews the limitations of ocular disease treatment, discusses the classification of NADs in ophthalmology, reveals the delivery strategies of NADs to improve bioavailability, targeting, and stability, and summarizes the mechanisms of NADs in ophthalmopathy.

Thrombospondin-1 induction and VEGF reduction by proteasome inhibition

The present study focuses on investigating the expression of thrombospondin-1 (TSP-1), a natural inhibitor of neovascularization. Immunofluorescent staining was used to detect the expression of TSP-1 in rabbit corneal tissue with vascularization induced by limbectomy. TSP-1 was detected in healthy and Cultured Autologous Oral Mucosal Epithelial Cell Sheet (CAOMECS) grafted rabbit corneas. TSP-1 was not detected in diseased corneas. Rabbit and human primary oral mucosal and corneal epithelial cells were cultured and treated with proteasome inhibitor (PI) in vitro. Changes in the expression of TSP-1, HIF-1 alpha and 2 alpha, VEGF-A, and VEGF receptor were analyzed by Western blotting. Neovascularization developed in rabbits' corneas as early as 1 month after limbectomy and was stable for at least 3 months. HIF-1 alpha and VEGF-A expression was reduced in CAOMECS grafted corneas, as compared to sham corneas. While TSP-1 expression was decreased in injured corneas, it was expressed in CAOMECS grafted corneas, but still less expressed compared to healthy corneas. PI treatment, of human oral mucosal and corneal epithelial cells increased TSP-1 expression and reduced VEGF-A expression. The results showed that TSP-1 expression was lost in injured corneal surface and that CAOMECS grafting restored TSP-1 expression to certain extent. Proteasome inhibition treatment increased TSP-1 and decreased VEGF-A expression in human oral mucosal and corneal epithelial cells. The result suggests that corneal neovascularization could be managed with the inhibition of the proteasome after CAOMECS grafting and increase corneal transparency.

Altered Regulation of mRNA and miRNA Expression in Epithelial and Stromal Tissue of Keratoconus Corneas

Purpose

Evaluation of mRNA and microRNA (miRNA) expression in epithelium and stroma of patients with keratoconus.

Methods

The epithelium and stroma of eight corneas of eight patients with keratoconus and eight corneas of eight non-keratoconus healthy controls were studied separately. RNA was extracted, and mRNA and miRNA analyses were performed using microarrays. Differentially expressed mRNAs and miRNAs in epithelial and stromal keratoconus samples compared to healthy controls were identified. Selected genes and miRNAs were further validated using RT-qPCR.

Results

We discovered 170 epithelial and 1498 stromal deregulated protein-coding mRNAs in KC samples. In addition, in epithelial samples 180 miRNAs and in stromal samples 379 miRNAs were significantly deregulated more than twofold compared to controls. Pathway analysis revealed enrichment of metabolic and axon guidance pathways for epithelial cells and enrichment of metabolic, mitogen-activated protein kinase (MAPK), and focal adhesion pathways for stromal cells.

Conclusions

This study demonstrates significant differences in the expression and regulation of mRNAs and miRNAs in the epithelium and stroma of Patients with KC. Also, in addition to the well-known target candidates, we were able to identify further genes and miRNAs that may be associated with keratoconus. Signaling pathways influencing metabolic changes and cell contacts are affected in epithelial and stromal cells of patients with keratoconus.

The Role of Connexin in Ophthalmic Neovascularization and the Interaction between Connexin and Proangiogenic Factors

The formation of new blood vessels is an important physiological process that occurs during development. When the body is injured, new blood vessel formation helps the body recuperate by supplying more oxygen and nutrients. However, this mechanism can have a negative effect. In ophthalmologic diseases, such as corneal new blood vessels, neonatal vascular glaucoma, and diabetes retinopathy, the formation of new blood vessels has become a critical component in patient survival. Connexin is a protein that regulates the cellular and molecular material carried by cells. It has been demonstrated that it is widely expressed in vascular endothelial cells, where it forms a slit connection between adjacent cells to promote cell-cell communication via hemichannels, as well as substance exchange into intracellular environments. Numerous studies have demonstrated that connexin in vascular endothelial cells plays an important role in angiogenesis and vascular leakage. The purpose of this study was to investigate the effect between the angiogenesis-associated factor and the connexin. It also reveals the effect of connexin on ophthalmic neovascularization.

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.

MicroRNAs Expression in Response to rhNGF in Epithelial Corneal Cells: Focus on Neurotrophin Signaling Pathway

PURPOSE

Nerve growth factor efficacy was demonstrated for corneal lesions treatment, and recombinant human NGF (rhNGF) was approved for neurotrophic keratitis therapy. However, NGF-induced molecular responses in cornea are still largely unknown. We analyzed microRNAs expression in human epithelial corneal cells after time-dependent rhNGF treatment.

METHODS

Nearly 700 microRNAs were analyzed by qRT-PCR. MicroRNAs showing significant expression differences were examined by DIANA-miRpath v.3.0 to identify target genes and pathways. Immunoblots were performed to preliminarily assess the strength of the in silico results.

RESULTS

Twenty-one microRNAs (miR-26a-1-3p, miR-30d-3p, miR-27b-5p, miR-146a-5p, miR-362-5p, mir-550a-5p, mir-34a-3p, mir-1227-3p, mir-27a-5p, mir-222-5p, mir-151a-5p, miR-449a, let7c-5p, miR-337-5p, mir-29b-3p, miR-200b-3p, miR-141-3p, miR-671-3p, miR-324-5p, mir-411-3p, and mir-425-3p) were significantly regulated in response to rhNGF. In silico analysis evidenced interesting target genes and pathways, including that of neurotrophin, when analyzed in depth. Almost 80 unique target genes (e.g., PI3K, AKT, MAPK, KRAS, BRAF, RhoA, Cdc42, Rac1, Bax, Bcl2, FasL) were identified as being among those most involved in neurotrophin signaling and in controlling cell proliferation, growth, and apoptosis. AKT and RhoA immunoblots demonstrated congruence with microRNA expression, providing preliminary validation of in silico data.

CONCLUSIONS

MicroRNA levels in response to rhNGF were for the first time analyzed in corneal cells. Novel insights about microRNAs, target genes, pathways modulation, and possible biological responses were provided. Importantly, given the putative role of microRNAs as biomarkers or therapeutic targets, our results make available data which might be potentially exploitable for clinical applications.

Relationship between miR-203a inhibition and oil-induced toxicity in early life stage zebrafish (Danio rerio)

Dysregulation of microRNA (miRNA, miR) by environmental stressors influences the transcription of mRNA which may impair organism development and/or lead to adverse physiological outcomes. Early studies evaluating the effects of oil on developmental toxicity in early life stages of fish showed that reductions in expression of miR-203a were associated with enhanced expression of downstream mRNAs that predicted altered eye development, cardiovascular disease, and improper fin development. To better understand the effects of miR-203a inhibition as an outcome of oil-induced toxicity in early life stage (ELS) fish, embryonic zebrafish were injected with an miR-203a inhibitor or treated with 3.5 µM phenanthrene (Phe) as a positive control for morphological alterations of cardiovascular and eye development caused by oil. Embryos treated with Phe had diminished levels of miR-203a at 7 and 72 h after injection. Embryos treated with the miR-203a inhibitor and Phe exhibited a reduced heart rate by 48 h post fertilization (hpf), with an increased incidence of developmental deformities (including pericardial edema, altered eye development, and spinal deformities) and reduced caudal fin length by 72 hpf. There were significant reductions in lens and eye diameters in 120 hpf miR-203a-inhibitor and Phe-treated fish, as well as a significantly reduced number of eye saccades, determined by an optokinetic response (OKR) behavioral assay. The expression of vegfa, which is an important activator during neovascularization, was significantly upregulated in embryos receiving miR-203a inhibitor injections by 7 and 72 hpf with increased trends in vegfa expression in 72 hpf larvae treated with Phe. There were decreasing trends in crx, neurod1, and pde6h expression by 72 hpf in miR-203a inhibitor and Phe treatments, which are involved in photoreceptor function in developing eyes and regulated by miR-203a. These results suggest that an inhibition of miR-203a in ELS fish exhibits an oil-induced toxic response that is consistent with Phe treatment and specifically impacts retinal, cardiac, and fin development in ELS fish.

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miR-203a inhibitor-injected zebrafish exhibited an oil-induced toxic response.

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Inhibition of miR-203a impaired retinal, cardiac, and fin development in zebrafish.

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miR-203a inhibition validated previously predicted transcriptomic pathways.

Suppression of the caspase-1/GSDMD-mediated pyroptotic signaling pathway through dexamethasone alleviates corneal alkali injuries

The pathological mechanism of corneal injuries mediated by alkali burns are associated with Nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain containing 3 protein (NLRP3)-related corneal sterile inflammation. Whether the executive protein gasdermin D (GSDMD) of pyroptosis mediated by the NLRP3 inflammasome is present in alkali-induced corneal lesions remains unclear. Dexamethasone (Dex) is a commonly used drug for ocular surface diseases that can maintain corneal transparency and anti-inflammatory effects by topical administration. Here, we presented evidence that the effect of Dex on the pyroptosis-related caspase-1/GSDMD pathway in corneal alkali burns (CABs). We assessed the clinical manifestations and histological characteristics of the placebo group, 0.05% Dex group, 0.1% Dex group on day 3 or day 7 postburn and the control group (healthy corneas). The expression of factors (including NLRP3, caspase-1, cleaved-caspase-1, GSDMD, GSDMD-N termini, pro-interleukin(IL)-1β, IL-1β, pro-IL-18 and IL-18) involved in the pyroptosis related caspase-1/GSDMD signaling pathway was demonstrated by molecular experiments in CAB. Alkali burns can upregulate the originally relatively dim expression of NLRP3, caspase-1, cleaved-caspase-1, GSDMD, GSDMD-N, pro-IL-1β, pro-IL-18, IL-1β and IL-18 in the healthy corneal epithelium and stroma. However, Dex can reverse the enhanced expression at the two timepoints. Corneal sterile inflammation can activate the NLRP3 inflammasome through the innate immune response mechanism and then activate the pyroptosis-related caspase-1/GSDMD signaling pathway. In addition, Dex can inhibit pyroptosis through this pathway.

Pathophysiology of aniridia-associated keratopathy: Developmental aspects and unanswered questions

Aniridia, a rare congenital disease, is often characterized by a progressive, pronounced limbal insufficiency and ocular surface pathology termed aniridia-associated keratopathy (AAK). Due to the characteristics of AAK and its bilateral nature, clinical management is challenging and complicated by the multiple coexisting ocular and systemic morbidities in aniridia. Although it is primarily assumed that AAK originates from a congenital limbal stem cell deficiency, in recent years AAK and its pathogenesis has been questioned in the light of new evidence and a refined understanding of ocular development and the biology of limbal stem cells (LSCs) and their niche. Here, by consolidating and comparing the latest clinical and preclinical evidence, we discuss key unanswered questions regarding ocular developmental aspects crucial to AAK. We also highlight hypotheses on the potential role of LSCs and the ocular surface microenvironment in AAK. The insights thus gained lead to a greater appreciation for the role of developmental and cellular processes in the emergence of AAK. They also highlight areas for future research to enable a deeper understanding of aniridia, and thereby the potential to develop new treatments for this rare but blinding ocular surface disease.

miR-340-5p mediates the therapeutic effect of mesenchymal stem cells on corneal neovascularization

BACKGROUND

Our previous study revealed that mesenchymal stem cells (MSCs) inhibited angiogenesis via miRNA-mediated repression of prospero homeobox 1 (PROX1). This study aimed to verify whether miR-340-5p participates in the therapeutic effect of MSCs on corneal neovascularization (CNV) via repressing PROX1 and epithelial membrane protein 2 (EMP2).

MATERIALS AND METHODS

The rat CNV model was established by corneal alkali burn. The binding relationship between miR-340-5p and 3'-untranslational regions (3'UTRs) of EMP2 and PROX1 was confirmed using dual-luciferase reporter assay. After culturing corneal epithelial cells (CECs) using MSC supernatants, the vascular endothelial growth factor (VEGF) level in CEC supernatants and the CEC viability were detected. The role of miR-340-5p in the therapeutic effect of MSC on CNV was determined via lentivirus-mediated miR-340-5p intervention in vivo.

RESULTS

The expression of miR-340-5p was reduced and EMP2 and PROX1 were increased in CNV corneal tissues. The lentivirus-mediated overexpression of miR-340-5p inhibited the expressions of EMP2 and PROX1. The dual-luciferase reporter assay confirmed that miR-340-5p could bind with the 3'UTRs of EMP2 and PROX1. miR-340-5p was enriched in MSC supernatants and the culture of CECs using MSC supernatants increased the miR-340-5p expression in CECs. After being cultured in miR-340-5p-knocking down MSC supernatants, the expressions of EMP2 and PROX1 were increased, and the VEGF level and CEC viability were restored. The in vivo experiments also indicated that the therapeutic effect of MSCs was mediated by miR-340-5p.

CONCLUSIONS

miR-340-5p mediates the therapeutic effect of MSCs on CNV via binding and repressing the expressions of EMP2 and PROX1.

Knockdown of lncRNA TUG1 suppresses corneal angiogenesis through regulating miR-505-3p/VEGFA

OBJECTIVES

Vascular endothelial growth factor A (VEGFA) is one of the major factors initiating and regulating angiogenesis. LncRNA taurine up-regulated gene 1 (TUG1) has been implicated in the pathological neovascularization. The aim of this study is to explore the function of TUG1 in regulating VEGFA-mediated angiogenesis in endothelial cells.

METHODS

A total of 12 corneal neovascularization (CRNV) samples were collected form patient undergoing corneal transplantation at Tongji Hospital, Wuhan, China. qRT-PCR and Western blotting were performed to examine gene expression and protein levels. Human umbilical vein endothelial cells (HUVECs) were used as an in vitro angiogenesis model. CCK-8 proliferation assay was used to determine cell proliferation capacity and wound healing was performed to analyze cell migration ability. Dual luciferase reporter assay was used for functional interaction validation between miR-505-3p and its targets. The in vitro angiogenic potential was evaluated by tube formation assay.

RESULTS

TUG1 and VEGFA were upregulated in CRNV tissues and VEGFA-treated HUVECs. TUG1 knockdown inhibited proliferation, migration and tube formation capacity of HUVECs. TUG1 regulated the angiogenesis of HUVECs by modulating VEGFA expression through targeting miR-505-3p.

CONCLUSIONS

Our results suggest that lncRNA TUG1 promotes the angiogenesis of HUVECs through modulating miR-505-3p/VEGFA axis.

Cell-Free Biological Approach for Corneal Stromal Wound Healing

Corneal opacification is the fourth most common cause of blindness globally behind cataracts, glaucoma, and age-related macular degeneration. The standard treatment of serious corneal scarring is corneal transplantation. Though it is effective for restoring vision, the treatment outcome is not optimal, due to limitations such as long-term graft survival, lifelong use of immunosuppressants, and a loss of corneal strength. Regulation of corneal stromal wound healing, along with inhibition or downregulation of corneal scarring is a promising approach to prevent corneal opacification. Pharmacological approaches have been suggested, however these are fraught with side effects. Tissue healing is an intricate process that involves cell death, proliferation, differentiation, and remodeling of the extracellular matrix. Current research on stromal wound healing is focused on corneal characteristics such as the immune response, angiogenesis, and cell signaling. Indeed, promising new technologies with the potential to modulate wound healing are under development. In this review, we provide an overview of cell-free strategies and some approaches under development that have the potential to control stromal fibrosis and scarring, especially in the context of early intervention.

The potential protective effects of miR-497 on corneal neovascularization are mediated via macrophage through the IL-6/STAT3/VEGF signaling pathway

Corneal neovascularization (CoNV) can cause abnormal blood vessels to grow in the transparent cornea, leading to various sight-threatening eye diseases. MicroRNAs are known to play essential roles in the regulation of numerous biological functions. We try to clarify the role of a specific microRNA, miR‑497, which has been shown to regulate the growth of tumor cells and angiogenesis on the basis of available data. However, the association between miR-497 and vascularized cornea remains unclear. Therefore, it is urgently needed to understand the molecular mechanism of miR497 in the progress of corneal neovascularization. Animal model of CoNV was established in wildtype (WT) C57BL/6 mice, CRISPR/Cas9 mediated miR-497 knockout (KO) and overexpressed (TG) C57BL/6 mice. MiR-497, expressed in corneas, was actively involved in alkali burn-induced corneal neovascularization via targeting STAT3 and negatively regulating its expression, attenuating macrophage infiltration and M2 polarization. Knockdown of miR-497 enhanced the formation of corneal angiogenesis through targeting STAT3 and facilitating its expression, promoting recruitment of macrophages, while overexpression of miR-497 restrained blood vessel sprouting via regulating downstream STAT3 and VEGFA expression, reducing macrophage activation and inhibiting M2 polarization. Moreover, miR-497 knockout-mediated damage effect can be rescued through the inhibition of STAT3 signaling. Mechanically, miR-497 might serve as a potential strategy for pathological corneal neovascularization via macrophage through the IL-6/STAT3/VEGFA signaling pathway.

Corneal angiogenic privilege and its failure

The cornea actively maintains its own avascular status to preserve its ultimate optical function. This corneal avascular state is also defined as "corneal angiogenic privilege", which results from a critical and sensitive balance between anti-angiogenic and pro-angiogenic mechanisms. In our review, we aim to explore the complex equilibrium among multiple mediators which prevents neovascularization in the resting cornea, as well as to unveil the evolutive process which leads to corneal angiogenesis in response to different injuries.

Regenerative Approaches and Future Trends for the Treatment of Corneal Burn Injuries

Ocular chemical and thermal burns are frequent causes of hospitalization and require immediate interventions and care. Various surgical and pharmacological treatment strategies are employed according to damage severity. Controlling inflammation and neovascularization while promoting normal ocular surface anatomy and function restoration is the principal aim. In the most severe cases, when epithelial healing is severely affected, reconstruction of the ocular surface may be a valid option, which, however, requires expertise, adequate instruments, and qualified donors. Numerous endogenous and exogenous strategies have been considered for corneal repair. Among these, stem cells and their derivatives have offered numerous attractive possibilities in finding an effective way in stimulating corneal regeneration. Limbal epithelial stem cells and mesenchymal cells from the ocular tissue as well as from various sources have demonstrated their effectiveness in dampening neovascularization, scarring, and inflammation, while promoting epithelialization of the injured cornea. Moreover, a plethora of cytokines and growth factors, and extracellular vesicles, which constitute the secretome of these cells, work in concert to enhance wound healing. In this review, we provide an update on the recent potential therapeutic avenues and clinical applications of stem cells and their products in corneal regeneration after burn injury, as well as current imaging strategies for monitoring therapeutic efficacy and damage resolution.

Therapeutic measures for sulfur mustard-induced ocular injury

The use of sulfur mustard (SM) in global terrorism is still a relevant threat to both civilian population and military personnel. Casualties exposed to SM may present mild, moderate or severe acute ocular lesions followed by a complete ocular resolution, chronic lesions or re-emerged ocular pathologies after a latent period. Current treatment for SM-induced ocular injury is based mainly on the clinical manifestation at the different stages of the injury and includes pharmaceutical and surgical interventions. These therapeutic measures are beneficial but not sufficient, and the ocular injury remains a continuous challenge for medical professionals. This review focuses on treatment experience carried out in humans and studied in animal models, for both SM-induced ocular acute injury and late pathology. In general, therapeutic measures are based on clinical features of the ocular injury or on the involvement of specific factors during the ocular injury that point out towards potential treatments. Anti-inflammatory treatments and limbal stem cell transplantation techniques were developed based on the clinical manifestation of the ocular injury. Optional therapies for impaired corneal innervation and endothelium are suggested for future research. Additionally, studies on potential treatments with anti-matrix metalloproteinase (MMP), anti-vascular endothelial growth factor (VEGF) and anti-IL-6 agents are discussed. Consequently, future studies may reveal the potential of additional pharmacological and biological treatments or advanced cellular and molecular biology methods to serve as novel therapeutic measures and techniques for this complicated ocular injury.

Therapeutic Potential of Extracellular Vesicles for the Treatment of Corneal Injuries and Scars

Infection, trauma, and chemical exposure of the ocular surface can severely damage the cornea, resulting in visually significant stromal scars. Current medical treatments are ineffective in mitigating corneal scarring, and corneal transplantation is the only therapy able to restore vision in these eyes. However, because of a severe shortage of corneal tissues, risks of blinding complications associated with corneal transplants, and a higher rate of graft failure in these eyes, an effective and deliverable alternative therapy for the prevention and treatment of corneal scarring remains a significant unmet medical need globally. In recent years, the therapeutic potential of extracellular vesicles (EVs) secreted by cells to mediate cell-cell communication has been a topic of increasing interest. EVs derived from mesenchymal stem cells, in particular human corneal stromal stem cells, have antifibrotic, anti-inflammatory, and regenerative effects in injured corneas. The exact mechanism of action of these functional EVs are largely unknown. Therapeutic development of EVs is at an early stage and warrants further preclinical studies.

Multimodal Photoacoustic Imaging-Guided Regression of Corneal Neovascularization: A Non-Invasive and Safe Strategy

Corneal neovascularization (CNV) is one of the main factors that induce blindness worldwide. However, current medical treatments cannot achieve non-invasive and safe inhibition of CNV. A noninvasive photoacoustic imaging (PAI)-guided method is purposed for the regression of CNV. PAI can monitor the oxygen saturation of cornea blood vessels through the endogenous contrast of hemoglobin and trace administrated drugs by themselves as exogenous contrast agents. An indocyanine green (ICG)-based nanocomposite (R-s-ICG) is prepared for CNV treatment via eye drops and subconjunctival injections. It is demonstrated that R-s-ICG can enrich corneal tissues and pathological blood vessels rapidly with minor residua in normal eyeball tissues. Anti-CNV treatment-driven changes in the blood vessels are assessed by real-time multimodal PAI in vivo, and then a safe laser irradiation strategy through the canthus is developed for phototherapy and gene therapy synergistic treatment. The treatment leads to the efficient inhibition of CNV with faint damages to normal tissues.

Abnormal neovascular and proliferative conjunctival phenotype in limbal stem cell deficiency is associated with altered microRNA and gene expression modulated by PAX6 mutational status in congenital aniridia

PURPOSE

To evaluate conjunctival cell microRNA (miRNAs) and mRNA expression in relation to observed phenotype of progressive limbal stem cell deficiency in a cohort of subjects with congenital aniridia with known genetic status.

METHODS

Using impression cytology, bulbar conjunctival cells were sampled from 20 subjects with congenital aniridia and 20 age and sex-matched healthy control subjects. RNA was extracted and miRNA and mRNA analyses were performed using microarrays. Results were related to severity of keratopathy and genetic cause of aniridia.

RESULTS

Of 2549 miRNAs, 21 were differentially expressed in aniridia relative to controls (fold change ≤ -1.5 or ≥ +1.5). Among these miR-204-5p, an inhibitor of corneal neovascularization, was downregulated 26.8-fold in severely vascularized corneas. At the mRNA level, 539 transcripts were differentially expressed (fold change ≤ -2 or ≥ +2), among these FOSB and FOS were upregulated 17.5 and 9.7-fold respectively, and JUN by 2.9-fold, all being components of the AP-1 transcription factor complex. Pathway analysis revealed enrichment of PI3K-Akt, MAPK, and Ras signaling pathways in aniridia. For several miRNAs and transcripts regulating retinoic acid metabolism, expression levels correlated with keratopathy severity and genetic status.

CONCLUSION

Strong dysregulation of key factors at the miRNA and mRNA level suggests that the conjunctiva in aniridia is abnormally maintained in a pro-angiogenic and proliferative state, and these changes are expressed in a PAX6 mutation-dependent manner. Additionally, retinoic acid metabolism is disrupted in severe, but not mild forms of the limbal stem cell deficiency in aniridia.

Pathogenesis of Herpes Stromal Keratitis: Immune Inflammatory Response Mediated by Inflammatory Regulators

Herpes stromal keratitis (HSK) is one of the primary diseases that cause vision loss or even blindness after herpes simplex virus (HSV)-1 infection. HSK-associated vision impairment is predominantly due to corneal scarring and neovascularization caused by inflammation. In the infected cornea, HSV can activate innate and adaptive immune responses of host cells, which triggers a cascade of reactions that leads to the release of inflammatory cytokines, chemokines, microRNA, and other regulatory factors that have stimulating or inhibitory effects on tissue. Physiologically, host cells show homeostasis. In this review, we summarize the factors involved in HSK pathogenesis from the perspective of immunity, molecules, and pathological angiogenesis. We also describe in detail the pathogenesis of chronic inflammatory lesions of the corneal stroma in response to HSV-1 infection.

MicroRNA Profiling of Highly Enriched Human Corneal Epithelial Stem Cells by Small RNA Sequencing

The objective of the study was to elucidate the microRNA (miRNA) profile of an enriched human corneal epithelial stem cell (CESC) population in comparison to differentiated central corneal epithelial cells (CCECs) by small RNA sequencing. The CESCs were enriched by differential enzymatic treatment to isolate the basal limbal epithelial cells followed by laser capture microdissection of cells with nucleus to cytoplasm ratio ≥0.7, from donor tissues. Small RNA sequencing was carried out using Illumina NextSeq. 500 platform and the validation of differentially expressed miRNAs by quantitative real-time PCR (qPCR) and locked nucleic acid miRNA in-situ hybridization (LNA-ISH). The sequencing identified 62 miRNAs in CESCs and 611 in CCECs. Six miRNAs: hsa-miR-21-5p, 3168, 143-3p, 10a-5p, 150-5p and 1910-5p were found to be significantly upregulated in enriched CESCs, which was further confirmed by qPCR and LNA-ISH. The expression of hsa-miR-143-3p was exclusive to clusters of limbal basal epithelial cells. The targets of the upregulated miRNAs were predicted to be associated with signaling pathways -Wnt, PI3K-AKT, MAPK and pathways that regulate pluripotency of stem cells, cell migration, growth and proliferation. Further studies are essential to elucidate their functional role in maintenance of stemness. The findings of the study also hypothesize the inherent potential of hsa-miR-143-3p to serve as a biomarker for identifying CESCs.

Controlled Release of rAAV Vectors from APMA-Functionalized Contact Lenses for Corneal Gene Therapy

As an alternative to eye drops and ocular injections for gene therapy, the aim of this work was to design for the first time hydrogel contact lenses that can act as platforms for the controlled delivery of viral vectors (recombinant adeno-associated virus, rAAV) to the eye in an effective way with improved patient compliance. Hydrogels of hydroxyethyl methacrylate (HEMA) with aminopropyl methacrylamide (APMA) (H₁: 40, and H₂: 80 mM) or without (H_c: 0 mM) were synthesized, sterilized by steam heat (121 °C, 20 min), and then tested for gene therapy using rAAV vectors to deliver the genes to the cornea. The hydrogels showed adequate light transparency, oxygen permeability, and swelling for use as contact lenses. Loading of viral vectors (rAAV-lacZ, rAAV-RFP, or rAAV-hIGF-I) was carried out at 4 °C to maintain viral vector titer. Release in culture medium was monitored by fluorescence with Cy3-rAAV-lacZ and AAV Titration ELISA. Transduction efficacy was tested through reporter genes lacZ and RFP in human bone marrow derived mesenchymal stem cells (hMSCs). lacZ was detected with X-Gal staining and quantified with Beta-Glo^®, and RFP was monitored by fluorescence. The ability of rAAV-hIGF-I-loaded hydrogels to trigger cell proliferation in hMSCs was evaluated by immunohistochemistry. Finally, the ability of rAAV-lacZ-loaded hydrogels to transduce bovine cornea was confirmed through detection with X-Gal staining of β-galactosidase expressed within the tissue.

Progress in Research on the Role of FGF in the Formation and Treatment of Corneal Neovascularization

Corneal neovascularization (CNV) is a sight-threatening disease usually associated with inflammatory, infectious, degenerative, and traumatic disorders of the ocular surface. Fibroblast growth factor (FGF) family members play an important role in angiogenesis to induce corneal neovascularization, which significantly affects the differentiation, proliferation, metastasis, and chemotaxis of vascular endothelial cells. Both acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) demonstrate positive staining in capillaries and induce corneal stromal cells. The anabolism of endothelial cells is induced by bFGF in corneal neovascularization. FGFs exert their effects via specific binding to cell surface-expressed specific receptors. We believe that both anti-FGF antibodies and anti-FGF receptor antibodies represent new directions for the treatment of CNV. Similar to anti-vascular endothelial growth factor antibodies, subconjunctival injection and eye drops can be considered effective forms of drug delivery.

MicroRNAs in Ocular Infection

MicroRNAs (miRNAs) are small, non-coding, regulatory RNA molecules and constitute a newly recognized, important layer of gene-expression regulation at post-transcriptional levels. miRNAs quantitatively fine tune the expression of their downstream genes in a cell type- and developmental stage-specific fashion. miRNAs have been proven to play important roles in the normal development and function as well as in the pathogenesis of diseases in all tissues and organ systems. miRNAs have emerged as new therapeutic targets and biomarkers for treatment and diagnosis of various diseases. Although miRNA research in ocular infection remains in its early stages, a handful of pioneering studies have provided insight into the roles of miRNAs in the pathogenesis of parasitic, fungal, bacterial, and viral ocular infections. Here, we review the current status of research in miRNAs in several major ocular infectious diseases. We predict that the field of miRNAs in ocular infection will greatly expand with the discovery of novel miRNA-involved molecular mechanisms that will inform development of new therapies and identify novel diagnostic biomarkers.