A key role of microRNA-26a in the scar formation after glaucoma filtration surgery

Wound Modulations in Glaucoma Surgery: A Systematic Review

Excessive fibrosis and resultant poor control of intraocular pressure (IOP) reduce the efficacy of glaucoma surgeries. Historically, corticosteroids and anti-fibrotic agents, such as mitomycin C (MMC) and 5-fluorouracil (5-FU), have been used to mitigate post-surgical fibrosis, but these have unpredictable outcomes. Therefore, there is a need to develop novel treatments which provide increased effectiveness and specificity. This review aims to provide insight into the pathophysiology behind wound healing in glaucoma surgery, as well as the current and promising future wound healing agents that are less toxic and may provide better IOP control.

Role of epigenetic regulation in glaucoma

Glaucoma is the world's leading irreversible blinding eye disease. Lowering intraocular pressure is currently the only effective clinical treatment. However, there is a lack of long-acting IOP-lowering drugs, and some patients still experience retinal ganglion cell loss even with good intraocular pressure control. Currently, there is no effective method for neuroprotection and regeneration in clinical practice for glaucoma. In recent years, epigenetics has been widely researched and reported for its role in glaucoma's neuroprotection and regeneration. This article reviews the changes in histone modifications, DNA methylation, non-coding RNA, and m6A methylation in glaucoma, aiming to provide new perspectives for glaucoma management, protection of retinal ganglion cells, and axon regeneration by understanding epigenetic alterations.

MiR-29b Downregulation by p53/Sp1 Complex Plays a Critical Role in Bleb Scar Formation After Glaucoma Filtration Surgery

Purpose

To investigate the function and mechanism of tumor protein p53 in pathological scarring after glaucoma filtration surgery (GFS) using human Tenon's fibroblasts (HTFs) and a rabbit GFS model.

Methods

The expression of p53 in bleb scarring after GFS and transforming growth factor-β (TGF-β)-induced HTFs (myofibroblasts [MFs]) was examined by western blot and immunochemical analysis. The interaction between p53 and specificity protein 1 (Sp1) was investigated by immunoprecipitation. The role of p53 and Sp1 in the accumulation of collagen type I alpha 1 chain (COL1A1) and the migration of MFs was evaluated by western blot, quantitative real-time polymerase chain reaction (qRT-PCR), wound healing, and Transwell assay. The regulatory mechanisms among p53/Sp1 and miR-29b were detected via qRT-PCR, western blot, luciferase reporter assay, and chromatin immunoprecipitation assay. The therapeutic effect of mithramycin A, a specific inhibitor of Sp1, on scarring formation was evaluated in a rabbit GFS model.

Results

p53 was upregulated in bleb scar tissue and MFs. p53 and Sp1 form a transcription factor complex that induces the accumulation of COL1A1 and promotes the migration of MFs through downregulation of miR-29b, a known suppressor of COL1A1. The p53/Sp1 axis inhibits miR-29b expression by the direct binding promoter of the miR-29b gene. Mithramycin A treatment attenuated bleb scar formation in vivo.

Conclusions

The p53/Sp1/miR-29b signaling pathway plays a critical role in bleb scar formation after GFS. This pathway could be targeted for therapeutic intervention of pathological scarring after GFS.

Translational Relevance

Our research indicates that inhibition of p53/Sp1/miR-29b is a promising therapeutic strategy for preventing post-GFS pathological scarring.

Role of the chloride channel blocker in the formation of filtering tract scars after glaucoma surgery in rats

Filtration surgery is commonly performed for glaucoma treatment to reduce intraocular pressure (IOP); however, scarring of the filtering bleb is the main cause of failure. In this study, we evaluated the effects of the chloride channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) on scar formation in filtering blebs. A glaucoma filtering surgery model was generated using Sprague-Dawley rats, divided into the control and NPPB groups receiving injections of different NPPB concentrations. The IOP of all rats decreased 1-day post-surgery and gradually increased afterward. However, IOP in rats from the NPPB groups recovered more slowly than that of the control group rats. In addition, the area and survival times of filtering blebs in rats from the NPPB groups were substantially larger and longer than those in the control group. Twenty-eight days after surgery, the protein and mRNA expression of collagen I, fibronectin and α-smooth muscle actin in the filtering area of rats from the NPPB groups were significantly lower than that in the control group rats. Collectively, our study demonstrates that NPPB inhibits filtering bleb scar formation, maintains filtering bleb morphology and prolongs filtering bleb survival time by inhibiting the differentiation of conjunctival fibroblasts and extracellular matrix synthesis.

Circ_0080940 Regulates miR-139-5p/CTGF Pathway to Promote the Proliferation, Migration, Extracellular Matrix Deposition of Human Tenon's Capsule Fibroblasts

PURPOSE

Circular RNA (circRNA) has been identified as an important regulator for glaucoma progression. Our study aims to reveal the circ_0080940 roles in glaucoma progression.

METHODS

Transforming growth factor β1 (TGF-β1) was used to treat human Tenon's capsule fibroblasts (HTFs) to mimic glaucoma cell models. Cell function was determined by cell counting kit 8 assay, EdU assay and wound healing assay. Protein levels were determined by western blot analysis. Quantitative real-time PCR was used to measure RNA expression. Dual-luciferase reporter assay was performed to evaluate RNA interaction.

RESULTS

Our data confirmed that TGF-β1 induced HTFs proliferation, migration and extracellular matrix (ECM) deposition. Circ_0080940 was highly expressed in glaucoma patients, and its knockdown inhibited TGF-β1-induced proliferation, migration and ECM deposition in HTFs. Circ_0080940 sponged miR-139-5p, and anti-miR-139-5p revoked the effect of si-circ_0080940 on the biological functions of TGF-β1-induced HTFs. CTGF was targeted by miR-139-5p, and overexpressed CTGF overturned the inhibition effect of miR-139-5p on the biological functions of TGF-β1-induced HTFs. Furthermore, CTGF expression could be positively regulated by circ_0080940.

CONCLUSION

To sum up, we confirmed that circ_0080940 contributed to glaucoma progression by miR-139-5p/CTGF axis.

Emerging Evidence of Noncoding RNAs in Bleb Scarring after Glaucoma Filtration Surgery

Purpose: To conduct a narrative review of research articles on the potential anti- and pro-fibrotic mechanisms of noncoding RNAs following glaucoma filtration surgery. Methods: Keyword searches of PubMed, and Medline databases were conducted for articles discussing post-glaucoma filtration surgeries and noncoding RNA. Additional manual searches of reference lists of primary articles were performed. Results: Fifteen primary research articles were identified. Four of the included papers used microarrays and qRT-PCR to identify up- or down-regulated microRNA (miRNA, miR) profiles and direct further study, with the remainder focusing on miRNAs or long noncoding RNAs (lncRNAs) based on previous work in other organs or disease processes. The results of the reviewed papers identified miR-26a, -29b, -139, -155, and -200a as having anti-fibrotic effects. In contrast, miRs-200b and -216b may play pro-fibrotic roles in filtration surgery fibrosis. lncRNAs including H19, NR003923, and 00028 have demonstrated pro-fibrotic effects. Conclusions: Noncoding RNAs including miRNAs and lncRNAs are emerging and promising therapeutic targets in the prevention of post-glaucoma filtration surgery fibrosis.

Collecting and deactivating TGF-β1 hydrogel for anti-scarring therapy in post-glaucoma filtration surgery

Scar formation can lead to glaucoma filtration surgery (GFS) failure, wherein transforming growth factor (TGF)-β is the core regulator. To reducing scar formation, this paper presents our study on the design of hydrogels to deactivate TGF-β1. We hypothesized that excess TGF-β1 can be removed from aqueous humor through the addition of oxidized hyaluronic acid (O-HA) hydrogels that are seeded with decorin (O-HA ​+ ​D). Immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) were performed to demonstrate the adsorption properties of O-HA ​+ ​D hydrogel, thus reducing the TGF-β1 concentration in aqueous humor. In the light that collagen contraction in human Tenon's capsule fibroblasts (HTFs) and the angiogenesis of human umbilical vein endothelial cells (HUVECs) can be activated by TGF-β1 and β2, we performed the quantitative analysis of polymerase chain reaction to determine the effect of O-HA ​+ ​D on the type I collagen, fibronectin, and angiogenesis. Our results illustrate that O-HA ​+ ​D can inhibit the increase of α-SMA expression in HTF induced by TGF-β1 and that O-HA ​+ ​D can inhibit the production of collagen I and fibronectin in HTF treated with TGF-β1. Furthermore, we performed in vivo studies by employing a rabbit model, where rabbits were treated with hydrogels post GFS. Our results demonstrate that, as compared with other groups, the rabbits treated with O-HA ​+ ​D had the greatest reduction in inflammatory cells with reduced level of collagen in wounds. Taken together, the present study paves the way toward the treatment of post-glaucoma fibrosis following surgery.

Treatment of hypertrophic scar with injection of triamcinolone leads to increased microRNA-26a in a rabbit ear model

Objectives:

Differential expression of microRNAs (miRNAs) has been confirmed to promote hypertrophic scar (HS) formation. However, this mechanism remains to be further elucidated. This paper investigated the effects of microRNA26a on HS of rabbit ears or its mechanism.

Methods:

The rabbit HS models were established and randomly assigned to either the experimental group (20 rabbits with treatment through triamcinolone acetonide) or the scar group (20 rabbits without treatment). In addition, 10 unmodeled rabbits were served as control group. The expression of microRNA-26a in HS tissues was detected via a stem-loop real-time polymerase chain reaction (RT-PCR).

Results:

According to RT-PCR, we showed the decreased expression of microRNA-26a in the scar group compared with that in the experimental group, and in the experimental group compared with that in the control group ( p < .01). In addition, the expression of microRNA-26a was negatively correlated with scar thickness (STs), number of fibroblasts (NFs), Collagen I (Col I) level, Collagen III (Col III) level, Interleukin-6 (IL-6) level, and Tumor necrosis factor-alpha (TNF-α) level (all p < .01).

Conclusions:

Our findings revealed that the increase of microRNA-26a expression might alleviate excessive inflammation during the HS formation, inhibit fibroblast proliferation and collagen deposition in HS, and promote the treatment of HS.

Pathogenesis and prospects for therapeutic clinical application of noncoding RNAs in glaucoma: Systematic perspectives

Noncoding ribonucleic acids (ncRNAs) are an increasingly studied class of RNA molecules with extensive biological activities, including important roles in human development, health, and disease. Glaucoma is a neurodegenerative disease of the retina, and one of the leading causes of blindness worldwide. However, the specific roles of ncRNAs in the development and progression of glaucoma are unclear, and related reports are fragmented. An in‐depth understanding of ncRNAs participating in the pathogenesis and progression of glaucoma would be helpful for opening up new avenues to facilitate the early diagnosis and clinical treatment. Therefore, in this review, we aimed to discuss the current research progress, the potentialfuture clinical applications and the research limitations of three critical classes of ncRNAs in glaucoma, namely microRNAs, long noncoding RNAs, and circular RNAs.

[Anti-scarring effect of rapamycin following filtering surgery in rabbit eyes]

OBJECTIVE

To study the effect of rapamycin on scar formation in rabbit eyes following filtering operation and explore the possible mechanism.

METHODS

Ninety-six healthy adult rabbits were subjected to trabeculectomy of the left eye and subsequently randomly divided into 4 groups (n=24) for treatment with castor oil (control) or rapamycin (1%, 3%, or 5%) eye drops of the operated eyes 4 times a day. The morphology and function of the filtering blebs of the rabbits were compared at 7, 14, 21 and 28 days after the operation; at each of the time points, 6 rabbits from each group were euthanized for detection of expressions of proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (α-SMA) in the tissues in the surgical area using immunohistochemistry. Cultured rabbit subconjunctival fibroblasts (RTFSs) were treated with different concentrations of rapamycin (0.06, 0.25, 1, and 4 mg/L) and the cell apoptosis was detected using flow cytometry.

RESULTS

In the first, second and third weeks after the operation, the rate of functional follicle formation was significantly higher in the 3 rapamycin groups than in the control group (P < 0.05), and the number of α- SMA-positive fibroblasts decreased over time in the 3 rapamycin groups. In cultured RTFSs, treatment with rapamycin at different concentrations resulted in increased apoptosis of the cells, and rapamycin above 0.25 mg/L significantly increased the cell apoptosis in a dose-dependent manner.

CONCLUSIONS

Rapamycin can inhibit hyperplasia of the filtering passage tissue, helps to preserve the functional filtering blebs and prolong their life span, and induces apoptosis of RTFS.

MicroRNA-26a inhibits hyperplastic scar formation by targeting Smad2

Hypertrophic scar (HS) is a fibrotic disease in which excessive extracellular matrix forms due to the response of fibroblasts to tissue damage. Novel evidence suggests that microRNAs (miRNAs or miRs) may contribute to hypertrophic scarring; however, the role of miRNAs in HS formation remains unclear. In the present study, miR-26a was significantly downregulated in HS tissues and human HS fibroblasts (hHSFs) was detected by reverse transcription-quantitative analysis. TargetScan was used to predict that mothers against decapentaplegic homolog 2 (Smad2) is a potential target gene of miR-26a and a dual-luciferase reporter assay confirmed that Smad2 was a target gene of miR-26a. The expression of Smad2 was upregulated in HS tissues and hHSFs. Cell Counting Kit-8 and flow cytometry analyses demonstrated that the overexpression of miR-26a significantly suppressed the proliferation ability of hHSFs and the apoptotic rate of hHSFs was significantly upregulated in response to miR-26a mimic transfection. Furthermore, the expression of B-cell lymphoma-2 (Bcl-2)-associated X protein was increased and Bcl-2 expression was decreased following miR-26a mimic transfection. The expression of collagens I and III was significantly inhibited following treatment with miR-26a mimics in hHSF cells. Conversely, miR-26a inhibitors served an opposing role in hHSFs. Furthermore, Smad2 overexpression enhanced the expression of collagens I and c III; however, Smad2 silencing inhibited the expression of collagens I and c III. In conclusion, the results of the present study indicate that miR-26a inhibits HS formation by modulating proliferation and apoptosis ad well as inhibiting the expression of extracellular matrix-associated proteins by targeting Smad2.