Epigenetic Landscape Analysis of the Long Non-Coding RNA and Messenger RNA in a Mouse Model of Corneal Alkali Burns

Exploring Corneal Neovascularization: An Integrated Approach Using Transcriptomics and Proteomics in an Alkali Burn Mouse Model

Purpose

Corneal neovascularization (CNV) impairs corneal transparency and visual acuity. The study aims to deepen our understanding of the molecules involved in CNV induced by alkali burns, facilitate a better grasp of CNV mechanisms, and uncover potential therapeutic targets.

Methods

Eighty-four mice were selected for establishing CNV models via alkali burns. On days 3, 7, and 14 after the burns, corneal observations and histological investigations were conducted. An integrated analysis of RNA sequencing (RNA-seq)-based transcriptomics and label-free quantitative proteomics was performed in both normal and burned corneas. Bioinformatics approaches, encompassing Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, were applied to discern differentially expressed genes (DEGs) and crucial signaling pathways. Four potentially CNV-related genes were validated using quantitative real-time PCR (qRT-PCR) and Western blot.

Results

Significant CNV was observed on the seventh day. Forty-one genes were differentially expressed in neovascularized corneas, with 15 upregulated and 26 downregulated at both mRNA and protein levels. Bioinformatics analysis revealed that these DEGs participated in diverse biological processes, encompassing retinol and retinoic acid metabolism, neutrophil chemotaxis, and actin filament assembly, along with significant enrichment pathways like cytochrome P450, tyrosine, and phenylalanine metabolism. The upregulation of lymphocyte cytosolic protein 1 (LCP1) and cysteine and glycine-rich protein 2 (CSRP2) genes and the downregulation of transglutaminase 2 (TGM2) and transforming growth factor-beta-induced (TGFBI) genes were confirmed.

Conclusions

We analyzed gene expression differences in mouse corneas 7 days after alkali burns, finding 41 genes with altered expression. The exact role of these genes in CNV is not fully understood, but exploring angiogenesis-related molecules offers potential for CNV treatment or prevention.

A moderate dosage of prostaglandin E2-mediated annexin A1 upregulation promotes alkali-burned corneal repair

Corneal alkali burn remains a clinical challenge in ocular emergency, necessitating the development of effective therapeutic drugs. Here, we observed the arachidonic acid metabolic disorders of corneas induced by alkali burns and aimed to explore the role of Prostaglandin E2 (PGE2), a critical metabolite of arachidonic acid, in the repair of alkali-burned corneas. We found a moderate dosage of PGE2 promoted the alkali-burned corneal epithelial repair, whereas a high dosage of PGE2 exhibited a contrary effect. This divergent effect is attributed to different dosages of PGE2 regulating ANXA1 expression differently. Mechanically, a high dosage of PGE2 induced higher GATA3 expression, followed by enhanced GATA3 binding to the ANXA1 promoter to inhibit ANXA1 expression. In contrast, a moderate dosage of PGE2 increased CREB1 phosphorylation and reduced GATA3 binding to the ANXA1 promoter, promoting ANXA1 expression. We believe PGE2 and its regulatory target ANXA1 could be potential drugs for alkali-burned corneas.

Pathogenesis of Alkali Injury-Induced Limbal Stem Cell Deficiency: A Literature Survey of Animal Models

Limbal stem cell deficiency (LSCD) is a debilitating ocular surface disease that eventuates from a depleted or dysfunctional limbal epithelial stem cell (LESC) pool, resulting in corneal epithelial failure and blindness. The leading cause of LSCD is a chemical burn, with alkali substances being the most common inciting agents. Characteristic features of alkali-induced LSCD include corneal conjunctivalization, inflammation, neovascularization and fibrosis. Over the past decades, animal models of corneal alkali burn and alkali-induced LSCD have been instrumental in improving our understanding of the pathophysiological mechanisms responsible for disease development. Through these paradigms, important insights have been gained with regards to signaling pathways that drive inflammation, neovascularization and fibrosis, including NF-κB, ERK, p38 MAPK, JNK, STAT3, PI3K/AKT, mTOR and WNT/β-catenin cascades. Nonetheless, the molecular and cellular events that underpin re-epithelialization and those that govern long-term epithelial behavior are poorly understood. This review provides an overview of the current mechanistic insights into the pathophysiology of alkali-induced LSCD. Moreover, we highlight limitations regarding existing animal models and knowledge gaps which, if addressed, would facilitate development of more efficacious therapeutic strategies for patients with alkali-induced LSCD.

Long Non-coding RNAs Gabarapl2 and Chrnb2 Positively Regulate Inflammatory Signaling in a Mouse Model of Dry Eye

Purpose: To elucidate the expression profile and the potential role of long non-coding ribonucleic acids (RNAs) (lncRNAs) in a dry eye disease (DED) model.

Methods: A DED model was established in C57BL/6J mice with 0.2% benzalkonium chloride (BAC) twice a day for 14 days. The differentially expressed lncRNAs were detected by RNA-seq technology (Gene Expression Omnibus, GEO GSE186450) and the aberrantly expressed lncRNAs were further verified by RT-qPCR. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to predicate the related candidate genes and potential pathological pathways. Cells from a human corneal epithelial cell line (HCECs) were cultured under hyperosmolarity. The regulation of inflammatory factors by silencing potential targeted lncRNAs was verified in vitro in HCECs.

Results: In our study, a significant increase in corneal fluorescence staining and a reduction in tear production were observed in DED mice at all follow-ups compared with the controls, and the differences were increasing over time. In total, 2,649 upregulated and 704 downregulated lncRNAs were identified in DED mice. We selected six aberrantly expressed and most abundant lncRNAs and performed RT-qPCR using the samples for RNA-seq. Chrnb2, Gabarapl2, and Usp31 were thereby confirmed as the most significantly altered lncRNAs. Pathway analysis revealed that the neuroactive ligand–receptor interaction signaling pathway was the most enriched, followed by the calcium signaling pathway and cytokine–cytokine receptor interaction. Following treatment of Gabarapl2 siRNA and Chrnb2 siRNA, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 were significantly downregulated in the HCECs.

Conclusion: Our study suggests that Chrnb2 and Gabarapl2 may be involved in the inflammation response by regulating TNF-α, IL-1β, and IL-6 in DED. These candidate lncRNAs may be both potential biomarkers and therapeutic targets for DED.

Long Noncoding RNA 3632454L22Rik Contributes to Corneal Epithelial Wound Healing by Sponging miR-181a-5p in Diabetic Mice

Purpose

This work explores the abnormal expression of long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and messenger RNAs (mRNAs) in diabetic corneal epithelial cells (CECs) and constructs an associated competitive endogenous RNA (ceRNA) network. Moreover, we revealed that Rik may exert advantageous effects on diabetic corneal epithelial wound closure by sponging miR-181a-5p.

Methods

We obtained the profiles of differentially expressed lncRNAs (DELs) of CECs of type 1 diabetic versus control corneas by microarray and summarized the differentially expressed miRNAs (DEmiRs) and differentially expressed genes (DEGs) data by published literature. Subsequently, the ceRNA network was constructed using bioinformatics analyses. The levels of lncRNA ENSMUST00000153610/3632454L22Rik (Rik) and miR-181a-5p were verified. The localization of Rik was identified with fluorescence in situ hybridization (FISH), and dual-luciferase assays proved the targeted relationship between Rik and miR-181a-5p. Furthermore, we validated the functional impact of Rik in vitro.

Results

Overall, 111 upregulated and 117 downregulated DELs were detected in diabetic versus control CECs. The level of Rik located in both the cytoplasm and the nucleus was clearly downregulated, whereas miR-181a-5p was upregulated in vitro and in vivo in the diabetic group versus the control group. Rik can act as a ceRNA to bind to miR-181a-5p, thus promoting diabetic corneal epithelial wound healing in vitro.

Conclusions

This work investigated the expression profile of DELs and constructed ceRNA networks of diabetic CECs for the first time. Furthermore, we revealed that Rik may positively impact diabetic corneal epithelial wound healing by sponging miR-181a-5p, providing a novel potential therapeutic target of diabetic keratopathy (DK).