METTL3 attenuates proliferative vitreoretinopathy and epithelial-mesenchymal transition of retinal pigment epithelial cells via wnt/β-catenin pathway

ABCA4 mediated traumatic proliferative vitreoretinopathy associated with PI3K/Akt signaling pathway

Background

Proliferative vitreoretinopathy (PVR) is the main cause of retinal detachment. However, the underlying mechanism of PVR is complex and has not yet been fully elucidated. The PI3K/Akt/mTOR signaling pathway is involved in angiogenesis and plays an important role in cell proliferation and tumor formation. Therefore, our study was designed to investigate the potential biological mechanisms of alleviating ARPE-19 cell and traumatic PVR model involving PI3K/Akt signaling pathway by targeting ABCA4.

Materials and methods

ARPE-19 cell model was induced by ABCA4 overexpression vector and si-ABCA4, then the ABCA4 overexpression vector and si-ABCA4 were constructed, the plasmids were expanded for cell transfection and verification. In addition, OE-ABCA4, shRNA NC and si-ABCA4 were transfected into ARPE-19 cells. Cell viability was detected by CCK-8 assay, cell cycle was determined by flow cytometry. The expression level and location of ABCA4 were detected by immunofluorescence. Finally, rabbit traumatic PVR model was induced by surgery, the adenovirus was injected into the vitreous body respectively, and the fundus observation was performed by direct ophthalmoscope observation combined with fundus photography, and the retinal routine histopathology HE staining was performed. Analysis of P21, CDK4, Cyclin D1, BAX, BAD, and ABCA4 was used by quantitative RT-PCR and Western blot. Besides, the expression level of ABCA4, AKT, p-AKT, PI3K, p-PI3K, P38, p-P38, JNK, p-JNK, ERK, and p-ERK was detected by Western blot.

Results

All results indicated that the viability of cells with high expression of ABC4A increased, while the viability of cells with inhibition of ABC4A decreased, the number of cells with high ABC4A expression was significantly higher, and the migration level of cells was significantly reduced after ABC4A inhibition (P < 0.05). ABC4A could affect cell apoptosis by affecting G1/G2 phase. The cell proliferation level was significantly increased with high expression of ABC4A. High expression of ABC4A increased phosphorylation levels, including p-AKT, p-PIK3, and p-P38, while inhibition of ABC4A decreased the expression levels of these proteins (P < 0.05). Inhibition of ABC4A could significantly improve retinopathy, indicating that the proliferation ability of cells was restored after inhibition of ABC4A.

Conclusions

Our finding suggested that inhibition of ABC4A ameliorated the injury degree of traumatic PVR and performed the potential anti-PVR effect via inhibiting PI3K/Akt signaling pathway, while promoting cell proliferation in both rabbit and ARPE-19 cells PVR model. The study has a certain innovation by building a traumatic PVR model to explore whether the ABCA4 participates in the regulation of the PI3K/AKT signaling pathway and the pathological mechanism of PVR regulation. At the same time, ABCA4's participation in the regulation of PI3K/Akt signaling pathway can prevent and delay the occurrence and development of PVR, which has positive significance for improving the survival rate and quality of life of patients, and also provides an important basis for its therapeutic mechanism. Therefore, our study demonstrated a significant strategy for inhibiting traumatic PVR via targeting PI3K/Akt/ABCA4 pathway.

RNA methylation-related inhibitors: Biological basis and therapeutic potential for cancer therapy

RNA methylation is widespread in nature. Abnormal expression of proteins associated with RNA methylation is strongly associated with a number of human diseases including cancer. Increasing evidence suggests that targeting RNA methylation holds promise for cancer treatment. This review specifically describes several common RNA modifications, such as the relatively well-studied N6-methyladenosine, as well as 5-methylcytosine and pseudouridine (Ψ). The regulatory factors involved in these modifications and their roles in RNA are also comprehensively discussed. We summarise the diverse regulatory functions of these modifications across different types of RNAs. Furthermore, we elucidate the structural characteristics of these modifications along with the development of specific inhibitors targeting them. Additionally, recent advancements in small molecule inhibitors targeting RNA modifications are presented to underscore their immense potential and clinical significance in enhancing therapeutic efficacy against cancer. KEY POINTS: In this paper, several important types of RNA modifications and their related regulatory factors are systematically summarised. Several regulatory factors related to RNA modification types were associated with cancer progression, and their relationships with cancer cell migration, invasion, drug resistance and immune environment were summarised. In this paper, the inhibitors targeting different regulators that have been proposed in recent studies are summarised in detail, which is of great significance for the development of RNA modification regulators and cancer treatment in the future.

TGF-β2-induced alterations of m6A methylation in hTERT RPE-1 cells

N6-methyladenosine (m6A) is a major type of RNA modification implicated in various pathophysiological processes. Transforming growth factor β2 (TGF-β2) induces epithelial-mesenchymal transition (EMT) in retinal pigmental epithelial (RPE) cells and promotes the progression of proliferative vitreoretinopathy (PVR). However, the role of m6A methylation in the EMT of human telomerase reverse transcriptase (hTERT) retinal pigmental epithelium (RPE)-1 cells has not been clarified. Here, we extracted RNA from RPE cells subjected to 0 or 20 ng/mL TGF-β2 for 72 h and identified differentially methylated genes (DMGs) by m6A-Seq and differentially expressed genes (DEGs) by RNA-Seq. We selected the genes related to EMT by conjoint m6A-Seq/RNA-Seq analysis and verified them by qRT-PCR. We then confirmed the function of m6A methylation in the EMT of RPE cells by knocking down the methyltransferase METTL3 and the m6A reading protein YTHDF1. Sequencing yielded 5814 DMGs and 1607 DEGs. Conjoint analysis selected 467 genes altered at the m6A and RNA levels that are closely associated with the EMT-related TGF-β, AGE-RAGE, PI3K-Akt, P53, and Wnt signaling pathways. We also identified ten core EMT genes ACTG2, BMP6, CDH2, LOXL2, SNAIL1, SPARC, BMP4, EMP3, FOXM1, and MYC. Their RNA levels were evaluated by qRT-PCR and were consistent with the sequencing results. We observed that METTL3 knockdown enhanced RPE cell migration and significantly upregulated the EMT markers N-cadherin (encoded by CDH2), fibronectin (FN), Snail family transcription repressor (SLUG), and vimentin. However, YTHDF1 knockdown had the opposite effects and decreased both cell migration and the N-cadherin, FN, and SLUG expression levels. The present study clarified TGF-β2-induced m6A- and RNA-level differences in RPE cells, indicated that m6A methylation might regulate EMT marker expression, and showed that m6A could regulate TGF-β2-induced EMT.

Lactylation-driven FTO targets CDK2 to aggravate microvascular anomalies in diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of irreversible vision loss in working-age populations. Fat mass and obesity-associated protein (FTO) is an N6-methyladenosine (m6A) demethylase that demethylates RNAs involved in energy homeostasis, though its influence on DR is not well studied. Herein, we detected elevated FTO expression in vitreous fibrovascular membranes of patients with proliferative DR. FTO promoted cell cycle progression and tip cell formation of endothelial cells (ECs) to facilitate angiogenesis in vitro, in mice, and in zebrafish. FTO also regulated EC-pericyte crosstalk to trigger diabetic microvascular leakage, and mediated EC-microglia interactions to induce retinal inflammation and neurodegeneration in vivo and in vitro. Mechanistically, FTO affected EC features via modulating CDK2 mRNA stability in an m6A-YTHDF2-dependent manner. FTO up-regulation under diabetic conditions was driven by lactate-mediated histone lactylation. FB23-2, an inhibitor to FTO's m6A demethylase activity, suppressed angiogenic phenotypes in vitro. To allow for systemic administration, we developed a nanoplatform encapsulating FB23-2 and confirmed its targeting and therapeutic efficiency in mice. Collectively, our study demonstrates that FTO is important for EC function and retinal homeostasis in DR, and warrants further investigation as a therapeutic target for DR patients.

N6-methyladenosine methylation in ophthalmic diseases: From mechanisms to potential applications

N6-methyladenosine (m6A) modification, as the most common modification method in eukaryotes, is widely involved in numerous physiological and pathological processes, such as embryonic development, malignancy, immune regulation, and premature aging. Under pathological conditions of ocular diseases, changes in m6A modification and its metabolism can be detected in aqueous and vitreous humor. At the same time, an increasing number of studies showed that m6A modification is involved in the normal development of eye structures and the occurrence and progress of many ophthalmic diseases, especially ocular neovascular diseases, such as diabetic retinopathy, age-related macular degeneration, and melanoma. In this review, we summarized the latest progress regarding m6A modification in ophthalmic diseases, changes in m6A modification-related enzymes in various pathological states and their upstream and downstream regulatory networks, provided new prospects for m6A modification in ophthalmic diseases and new ideas for clinical diagnosis and treatment.

MeCP2-Induced Alternations of Transcript Levels and m6A Methylation in Human Retinal Pigment Epithelium Cells

MeCP2 is a transcriptional regulator that is involved in epithelial-mesenchymal transition (EMT) and is highly expressed in proliferative vitreoretinopathy. m6A methylation is a critical post-transcriptional regulation in eukaryotic cells. However, the connection between MeCP2 and m6A methylation has not been revealed in retinal pigment epithelium (RPE), and the regulatory role of MeCP2 at the post-transcriptional level in an m6A-dependent manner is rarely investigated. In this study, we used sequencing to reveal differences in transcript levels and m6A abundance of individual genes in RPE cells after treatment with human recombinant protein MeCP2. The biological functions and processes of differential genes were further analyzed by bioinformatics. The results exhibited that after MeCP2 treatment, 65 genes were up-regulated and 43 genes were down-regulated at the transcription level, and 4 peaks were hypermethylated and 9,041 peaks were hypomethylated at the m6A modification level. Enrichment analysis found that differentially expressed genes were associated with organic acid metabolism, melanogenesis, and vascular smooth muscle contraction. In addition, differentially methylated genes were related to cell junction, RNA processing and metabolism, cell activity, actin cytoskeleton, and several signaling pathways associated with EMT. Further conjoint analysis indicated that the transcription and m6A levels of the EGR1, ELOVL2, and SFR1 genes were altered, and EGR1 is an essential transcription factor in the EMT process. The RNA levels and m6A levels of the three genes were verified by qPCR and m6A-IP-qPCR, respectively. Overall, this study preliminarily revealed the differential mapping of MeCP2-induced m6A modifications, which contributes to the study of the epigenetic and EMT mechanism in RPE cells.

Targeting non-muscle myosin II inhibits proliferative vitreoretinopathy through regulating epithelial-mesenchymal transition

Proliferative vitreoretinopathy (PVR) is a common complication of rhegmatogenous retinal detachment, eventually leading to vision loss. To date, there are no effective drugs for the treatment of this disease. In this study, we investigated the effect of blebbistatin, a non-muscle myosin II inhibitor, on the ARPE-19 cell line and in a rabbit model of proliferative vitreoretinopathy. In vitro, we found that blebbistatin inhibited the epithelial-mesenchymal transition of retinal pigment epithelial (RPE) cells and inhibited the ability of RPE cells to migrate, proliferate, generate extracellular matrix, and affect contractility. In vivo the PVR model showed that blebbistatin significantly delayed PVR progression. It also partially prevents the loss of retinal function caused by PVR. Our results suggest that blebbistatin is a potential drug with clinical applications for the treatment of PVR.

m6A mRNA Methylation Analysis Provides Novel Insights into Pigmentation in Sheep Skin

N6-methyladenosine (m⁶A) is the most universal post-transcriptional modification of mRNA which may play important roles in verious species. However, the potential roles of m⁶A in the pigmentation of skin are not completely understood. To explore the role of m6A modification in pigmentation of sheep skin, we used MeRIP-seq and RNA-seq to profile the skin transcriptome in black and white coat color (n=3). Our results showed that an average of 7701 m⁶A peaks were obtained for all samples and the average length was 305.89 bp. The GGACUU sequence was the most enrichment motif and shared in black skin and white skin. The m⁶A peaks were mainly enriched in the CDS, 3'UTR and 5'UTR, especially in CDS region near the stop codon of the transcript. 235 significantly differential peaks were found in black skin vs. white skin. The KEGG signaling pathways of downregulated and upregulated m⁶A peaks were mainly enriched in AGE-RAGE signaling pathway in diabetic complications, Viral carcinogenesis, Transcriptional misregulation in cancer, ABC transporters, Basal transcription factors and Thyroid hormone synthesis (P value <0.05). For RNA-seq, 71 differently expressed genes (DEGs) were scanned in black skin vs. white skin. DEGs were significantly enriched in tyrosine metabolism, melanogenesis, neuroactive ligand-receptor interaction pathway (P value <0.05). Combined m⁶A-seq and RNA-seq analysis showed that the hyper-up genes and hypo-up genes were both enriched in ErbB signaling pathway (P value <0.05). In conclusion, it provide a basis for further research into the functions of m⁶A methylation modifications in pigmentation.

Emerging role of m6A modification in fibrotic diseases and its potential therapeutic effect

Fibrosis can occur in a variety of organs such as the heart, lung, liver and kidney, and its pathological changes are mainly manifested by an increase in fibrous connective tissue and a decrease in parenchymal cells in organ tissues, and continuous progression can lead to structural damage and organ hypofunction, or even failure, seriously threatening human health and life. N6-methyladenosine (m6A) modification, as one of the most common types of internal modifications of RNA in eukaryotes, exerts a multifunctional role in physiological and pathological processes by regulating the metabolism of RNA. With the in-depth understanding and research of fibrosis, we found that m6A modification plays an important role in fibrosis, and m6A regulators can further participate in the pathophysiological process of fibrosis by regulating the function of specific cells. In our review, we summarized the latest research advances in m6A modification in fibrosis, as well as the specific functions of different m6A regulators. In addition, we focused on the mechanisms and roles of m6A modification in cardiac fibrosis, liver fibrosis, pulmonary fibrosis, renal fibrosis, retinal fibrosis and oral submucosal fibrosis, with the aim of providing new insights and references for finding potential therapeutic targets for fibrosis. Finally, we discussed the prospects and challenges of targeted m6A modification in the treatment of fibrotic diseases.

In vitro laboratory models of proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR), the most common cause of recurrent retinal detachment, is characterized by the formation and contraction of fibrotic membranes on the surface of the retina. There are no Food and Drug Administration (FDA)-approved drugs to prevent or treat PVR. Therefore, it is necessary to develop accurate in vitro models of the disease that will enable researchers to screen drug candidates and prioritize the most promising candidates for clinical studies. We provide a summary of recent in vitro PVR models, as well as avenues for model improvement. Several in vitro PVR models were identified, including various types of cell cultures. Additionally, novel techniques that have not been used to model PVR were identified, including organoids, hydrogels, and organ-on-a-chip models. Novel ideas for improving in vitro PVR models are highlighted. Researchers may consult this review to help design in vitro models of PVR, which will aid in the development of therapies to treat the disease.

The roles of METTL3 on autophagy and proliferation of vascular smooth muscle cells are mediated by mTOR rather than by CDK1

BACKGROUND

Aberrant proliferation of vascular smooth muscle cells (VSMCs) is the cause of neointima formation followed by vascular injury. Autophagy is involved in this pathological process, but its function is controversial. Recently, we found that methyltransferase like 3 (METTL3) inhibited VSMC proliferation by activating autophagosome formation. Moreover, we also demonstrated that METTL3 reduced the levels of phosphorylated mammalian target of rapamycin (p-mTOR) and cyclin dependent kinase 1 (p-CDK1/CDC2), which were critical for autophagy and proliferation regulation. However, whether mTOR and CDK1 mediated the function of METTL3 on autophagy and proliferation in VSMCs remains unknown.

RESULTS

We showed that the activator of mTOR, MHY1485 largely reversed the effects of METTL3 overexpression on VSMC autophagy and proliferation. Rapamycin, the inhibitor of mTOR, obviously nullified the pro-proliferation effects of METTL3 knockdown by activating autophagy in VSMCs. Unexpectedly, mTOR did not contribute to the impacts of METTL3 on migration and phenotypic switching of VSMCs. On the other hand, by knockdown of CDK1 in VSMC with METTL3 deficiency, we demonstrated that CDK1 was involved in METTL3-regulated proliferation of VSMCs, but this effect was not mediated by autophagy.

CONCLUSIONS

We concluded that mTOR but not CDK1 mediated the role of METTL3 on VSMC proliferation and autophagy.

METTL3-mediated m6A modification of HMGA2 mRNA promotes subretinal fibrosis and epithelial-mesenchymal transition

Subretinal fibrosis is a major cause of the poor visual prognosis for patients with neovascular age-related macular degeneration (nAMD). Myofibroblasts originated from retinal pigment epithelial (RPE) cells through epithelial-mesenchymal transition (EMT) contribute to the fibrosis formation. N6-Methyladenosine (m6A) modification has been implicated in the EMT process and multiple fibrotic diseases. The role of m6A modification in EMT-related subretinal fibrosis has not yet been elucidated. In this study, we found that during subretinal fibrosis in the mouse model of laser-induced choroidal neovascularization, METTL3 was upregulated in RPE cells. Through m6A epitranscriptomic microarray and further verification, high-mobility group AT-hook 2 (HMGA2) was identified as the key downstream target of METTL3, subsequently activating potent EMT-inducing transcription factor SNAIL. Finally, by subretinal injections of adeno-associated virus vectors, we confirmed that METTL3 deficiency in RPE cells could efficiently attenuate subretinal fibrosis in vivo. In conclusion, our present research identified an epigenetic mechanism of METTL3-m6A-HMGA2 in subretinal fibrosis and EMT of RPE cells, providing a novel therapeutic target for subretinal fibrosis secondary to nAMD.

ALKBH5 causes retinal pigment epithelium anomalies and choroidal neovascularization in age-related macular degeneration via the AKT/mTOR pathway

Retinal pigment epithelium (RPE) dysfunction and choroidal neovascularization (CNV) are predominant features of age-related macular degeneration (AMD), with an unclear mechanism. Herein, we show that RNA demethylase α-ketoglutarate-dependent dioxygenase alkB homolog 5 (ALKBH5) is up-regulated in AMD. In RPE cells, ALKBH5 overexpression associates with depolarization, oxidative stress, disturbed autophagy, irregular lipid homeostasis, and elevated VEGF-A secretion, which subsequently promotes proliferation, migration, and tube formation of vascular endothelial cells. Consistently, ALKBH5 overexpression in mice RPE correlates with various pathological phenotypes, including visual impairments, RPE anomalies, choroidal neovascularization (CNV), and interrupted retinal homeostasis. Mechanistically, ALKBH5 regulates retinal features through its demethylation activity. It targets PIK3C2B and regulates the AKT/mTOR signaling pathway with YTHDF2 as the N⁶-methyladenosine reader. IOX1, an ALKBH5 inhibitor, suppresses hypoxia-induced RPE dysfunction and CNV progression. Collectively, we demonstrate that ALKBH5 induces RPE dysfunction and CNV progression in AMD via PIK3C2B-mediated activation of the AKT/mTOR pathway. Pharmacological inhibitors of ALKBH5, like IOX1, are promising therapeutic options for AMD.

Epigenetic modifications and metabolic memory in diabetic retinopathy: beyond the surface

Epigenetics focuses on DNA methylation, histone modification, chromatin remodeling, noncoding RNAs, and other gene regulation mechanisms beyond the DNA sequence. In the past decade, epigenetic modifications have drawn more attention as they participate in the development and progression of diabetic retinopathy despite tight control of glucose levels. The underlying mechanisms of epigenetic modifications in diabetic retinopathy still urgently need to be elucidated. The diabetic condition facilitates epigenetic changes and influences target gene expression. In this review, we summarize the involvement of epigenetic modifications and metabolic memory in the development and progression of diabetic retinopathy and propose novel insights into the treatment of diabetic retinopathy.

Role of m6A methylation in retinal diseases

Retinal diseases remain among the leading causes of visual impairment in developed countries, despite great efforts in prevention and early intervention. Due to the limited efficacy of current retinal therapies, novel therapeutic methods are urgently required. Over the past two decades, advances in next-generation sequencing technology have facilitated research on RNA modifications, which can elucidate the relevance of epigenetic mechanisms to disease. N6-methyladenosine (m6A), formed by methylation of adenosine at the N6-position, is the most widely studied RNA modification and plays an important role in RNA metabolism. It is dynamically regulated by writers (methyltransferases) and erasers (demethylases), and recognized by readers (m6A binding proteins). Although the discovery of m6A methylation can be traced back to the 1970s, its regulatory roles in retinal diseases are rarely appreciated. Here, we provide an overview of m6A methylation, and discuss its effects and possible mechanisms on retinal diseases, including diabetic retinopathy, age-related macular degeneration, retinoblastoma, retinitis pigmentosa, and proliferative vitreoretinopathy. Furthermore, we highlight potential agents targeting m6A methylation for retinal disease treatment and discuss the limitations and challenges of research in the field of m6A methylation.

METTL3 Mediates Epithelial-Mesenchymal Transition by Modulating FOXO1 mRNA N6 -Methyladenosine-Dependent YTHDF2 Binding: A Novel Mechanism of Radiation-Induced Lung Injury

The biological roles of epithelial-mesenchymal transition (EMT) in the pathogenesis of radiation-induced lung injury (RILI) have been widely demonstrated, but the mechanisms involved have been incompletely elucidated. N⁶ -methyladenosine (m⁶ A) modification, the most abundant reversible methylation modification in eukaryotic mRNAs, plays vital roles in multiple biological processes. Whether and how m⁶ A modification participates in ionizing radiation (IR)-induced EMT and RILI remain unclear. Here, significantly increased m⁶ A levels upon IR-induced EMT are detected both in vivo and in vitro. Furthermore, upregulated methyltransferase-like 3 (METTL3) expression and downregulated α-ketoglutarate-dependent dioxygenase AlkB homolog 5 (ALKBH5) expression are detected. In addition, blocking METTL3-mediated m⁶ A modification suppresses IR-induced EMT both in vivo and in vitro. Mechanistically, forkhead box O1 (FOXO1) is identified as a key target of METTL3 by a methylated RNA immunoprecipitation (MeRIP) assay. FOXO1 expression is downregulated by METTL3-mediated mRNA m⁶ A modification in a YTH-domain family 2 (YTHDF2)-dependent manner, which subsequently activates the AKT and ERK signaling pathways. Overall, the present study shows that IR-responsive METTL3 is involved in IR-induced EMT, probably by activating the AKT and ERK signaling pathways via YTHDF2-dependent FOXO1 m⁶ A modification, which may be a novel mechanism involved in the occurrence and development of RILI.

GSK-3 inhibition reverts mesenchymal transition in primary human corneal endothelial cells

Human corneal endothelial cells are organized in a tight mosaic of hexagonal cells and serve a critical function in maintaining corneal hydration and clear vision. Regeneration of the corneal endothelial tissue is hampered by its poor proliferative capacity, which is partially retrieved in vitro, albeit only for a limited number of passages before the cells undergo mesenchymal transition (EnMT). Although different culture conditions have been proposed in order to delay this process and prolong the number of cell passages, EnMT has still not been fully understood and successfully counteracted. In this perspective, we identified herein a single GSK-3 inhibitor, CHIR99021, able to revert and avoid EnMT in primary human corneal endothelial cells (HCEnCs) from old donors until late passages in vitro (P8), as shown from cell morphology analysis (circularity). In accordance, CHIR99021 reduced expression of α-SMA, an EnMT marker, while restored endothelial markers such as ZO-1, Na⁺/K⁺ ATPase and N-cadherin, without increasing cell proliferation. A further analysis on RNA expression confirmed that CHIR99021 induced downregulation of EnMT markers (α-SMA and CD44), upregulation of the proliferation repressor p21 and revealed novel insights into the β-catenin and TGFβ pathways intersections in HCEnCs. The use of CHIR99021 sheds light on the mechanisms involved in EnMT, providing a substantial advantage in maintaining primary HCEnCs in culture until late passages, while preserving the correct morphology and phenotype. Altogether, these results bring crucial advancements towards the improvement of the corneal endothelial cells based therapy.

Inhibition of Ribosomal RNA Processing 15 Homolog (RRP15) Suppressed Tumor Growth, Invasion and Epithelial to Mesenchymal Transition (EMT) of Colon Cancer

Although ribosomal RNA processing 15 Homolog (RRP15) has been implicated in the occurrence of various cancers and is considered a potential target for cancer treatment, its significance in colon cancer (CC) is unclear. Thus, this present study aims to determine RRP15 expression and biological function in CC. The results demonstrated a strong expression of RRP15 in CC compared to normal colon specimens, which was correlated with poorer overall survival (OS) and disease-free survival (DFS) of the patients. Among the nine investigated CC cell lines, RRP15 demonstrated the highest and lowest expression in HCT15 and HCT116 cells, respectively. In vitro assays demonstrated that the knockdown of RRP15 inhibited the growth, colony-forming ability and invasive ability of the CC cells whereas its overexpression enhanced the above oncogenic function. Moreover, subcutaneous tumors in nude mice showed that RRP15 knockdown inhibited the CC growth while its overexpression enhanced their growth. Additionally, the knockdown of RRP15 inhibited the epithelial-mesenchymal transition (EMT), whereas overexpression of RRP15 promoted the EMT process in CC. Collectively, inhibition of RRP15 suppressed tumor growth, invasion and EMT of CC, and might be considered a promising therapeutic target for treating CC.

Methyltransferase-like 3 suppresses phenotypic switching of vascular smooth muscle cells by activating autophagosome formation

Prevention of neointima formation is the key to improving long-term outcomes after stenting or coronary artery bypass grafting. RNA N⁶ -methyladenosine (m⁶ A) methylation has been reported to be involved in the development of various cardiovascular diseases, but whether it has a regulatory effect on neointima formation is unknown. Herein, we revealed that methyltransferase-like 3 (METTL3), the major methyltransferase of m⁶ A methylation, was downregulated during vascular smooth muscle cell (VSMC) proliferation and neointima formation. Knockdown of METTL3 facilitated, while overexpression of METTL3 suppressed the proliferation of human aortic smooth muscle cells (HASMCs) by arresting HASMCs at G2/M checkpoint and the phosphorylation of CDC2 (p-CDC2) was inactivated by METTL3. On the other hand, the migration and synthetic phenotype of HASMCs were enhanced by METTL3 knockdown, but inhibited by METTL3 overexpression. The protein levels of matrix metalloproteinase 2 (MMP2), MMP7 and MMP9 were reduced, while the expression level of tissue inhibitor of metalloproteinase 3 was increased in HASMCs with METTL3 overexpression. Moreover, METTL3 promoted the autophagosome formation by upregulating the expression of ATG5 (autophagy-related 5) and ATG7. Knockdown of either ATG5 or ATG7 largely reversed the regulatory effects of METTL3 overexpression on phenotypic switching of HASMCs, as evidenced by increased proliferation and migration, and predisposed to synthetic phenotype. These results indicate that METTL3 inhibits the phenotypic switching of VSMCs by positively regulating ATG5-mediated and ATG7-mediated autophagosome formation. Thus, enhancing the level of RNA m⁶ A or the formation of autophagosomes is the promising strategy to delay neointima formation.

Integrated bioinformatical analysis, machine learning and in vitro experiment-identified m6A subtype, and predictive drug target signatures for diagnosing renal fibrosis

Renal biopsy is the gold standard for defining renal fibrosis which causes calcium deposits in the kidneys. Persistent calcium deposition leads to kidney inflammation, cell necrosis, and is related to serious kidney diseases. However, it is invasive and involves the risk of complications such as bleeding, especially in patients with end-stage renal diseases. Therefore, it is necessary to identify specific diagnostic biomarkers for renal fibrosis. This study aimed to develop a predictive drug target signature to diagnose renal fibrosis based on m6A subtypes. We then performed an unsupervised consensus clustering analysis to identify three different m6A subtypes of renal fibrosis based on the expressions of 21 m6A regulators. We evaluated the immune infiltration characteristics and expression of canonical immune checkpoints and immune-related genes with distinct m6A modification patterns. Subsequently, we performed the WGCNA analysis using the expression data of 1,611 drug targets to identify 474 genes associated with the m6A modification. 92 overlapping drug targets between WGCNA and DEGs (renal fibrosis vs. normal samples) were defined as key drug targets. A five target gene predictive model was developed through the combination of LASSO regression and stepwise logistic regression (LASSO-SLR) to diagnose renal fibrosis. We further performed drug sensitivity analysis and extracellular matrix analysis on model genes. The ROC curve showed that the risk score (AUC = 0.863) performed well in diagnosing renal fibrosis in the training dataset. In addition, the external validation dataset further confirmed the outstanding predictive performance of the risk score (AUC = 0.755). These results indicate that the risk model has an excellent predictive performance for diagnosing the disease. Furthermore, our results show that this 5-target gene model is significantly associated with many drugs and extracellular matrix activities. Finally, the expression levels of both predictive signature genes EGR1 and PLA2G4A were validated in renal fibrosis and adjacent normal tissues by using qRT-PCR and Western blot method.

METTL3 plays a crucial function in multiple biological processes

The N6-methyladenosine (m⁶A) refers to the methylation of the N6 position of adenosine of RNA adenine. The modification of m⁶A is one of the most abundant epigenetic modifications in eukaryotic mRNA and non-coding RNA and is controlled by methyltransferases and demethylases. The biological mechanism and significance of m⁶A have been discovered with the development of m⁶A sequencing. Various m⁶A complex components regulate the function of m⁶A on mRNA. Methyltransferase-like 3 (METTL3) is one of the earliest identified m⁶A methyltransferases which regulate the functions of m⁶A. A large number of studies have shown that METTL3 establishes a cross-talk with tumor cells and development of various human diseases. In this review, we will briefly elaborate on the role of METTL3 in biological function, epithelial-mesenchymal transition (EMT), inflammatory response and sensitivity to the resistance of chemo radiotherapies. The underlying molecular mechanism demonstrated by METTL3 may provide a possible target for treating and diagnosing human diseases.

Translational and clinical advancements in management of proliferative vitreoretinopathy

PURPOSE OF REVIEW

Despite advancement in the surgical instrumentation and techniques, proliferative vitreoretinopathy (PVR) remains the most common cause for failure of rhegmatogenous retinal detachment (RRD) repair. This review discusses ongoing translational and clinical advancements in PVR.

RECENT FINDINGS

PVR represents an exaggerated and protracted scarring process that can occur after RRD. The primary cell types involved are retinal pigment epithelium, glial, and inflammatory cells. They interact with growth factors and cytokines derived from the breakdown of the blood-retinal barrier that trigger a cascade of cellular processes, such as epithelial-mesenchymal transition, cell migration, chemotaxis, proliferation, elaboration of basement membrane and collagen and cellular contraction, leading to overt retinal pathology. Although there are currently no medical therapies proven to be effective against PVR in humans, increased understanding of the risks factors and pathophysiology have helped guide investigations for molecular targets of PVR. The leading therapeutic candidates are drugs that mitigate growth factors, inflammation, and proliferation are the leading therapeutic candidates.

SUMMARY

Although multiple molecular targets have been investigated to prevent and treat PVR, none have yet demonstrated substantial evidence of clinical benefit in humans though some show promise. Advancements in our understanding of the pathophysiology of PVR may help develop a multipronged approach for this condition.

METTL3-m6 A methylase regulates the osteogenic potential of bone marrow mesenchymal stem cells in osteoporotic rats via the Wnt signalling pathway

OBJECTIVES

Bone marrow mesenchymal stem cells (BMSCs) hold a high osteogenic differentiation potential, but the mechanisms that control the osteogenic ability of BMSCs from osteoporosis (OP-BMSCs) need further research. The purpose of this experiment is to discuss the osteogenic effect of Mettl3 on OP-BMSCs and explore new therapeutic target that can enhance the bone formation ability of OP-BMSCs.

MATERIALS AND METHODS

The bilateral ovariectomy (OVX) method was used to establish the SD rat OP model. Dot blots were used to reveal the different methylation levels of BMSCs and OP-BMSCs. Lentiviral-mediated overexpression of Mettl3 was applied in OP-BMSCs. QPCR and WB detected the molecular changes of osteogenic-related factors and Wnt signalling pathway in vitro experiment. The staining of calcium nodules and alkaline phosphatase detected the osteogenic ability of OP-BMSCs. Micro-CT and histological examination evaluated the osteogenesis of Mettl3 in OP rats in vivo.

RESULTS

The OP rat model was successfully established by OVX. Methylation levels and osteogenic potential of OP-BMSCs were decreased in OP-BMSCs. In vitro experiment, overexpression of Mettl3 could upregulate the osteogenic-related factors and activate the Wnt signalling pathway in OP-BMSCs. However, osteogenesis of OP-BMSCs was weakened by treatment with the canonical Wnt inhibitor Dickkopf-1. Micro-CT showed that the Mettl3(+) group had an increased amount of new bone formation at 8 weeks. Moreover, the results of histological staining were the same as the micro-CT results.

CONCLUSIONS

Taken together, the methylation levels and osteogenic potential of OP-BMSCs were decreased in OP-BMSCs. In vitro and in vivo studies, overexpression of Mettl3 could partially rescue the decreased bone formation ability of OP-BMSCs by the canonical Wnt signalling pathway. Therefore, Mettl3 may be a key targeted gene for bone generation and therapy of bone defects in OP patients.

Emerging Role of Epitranscriptomics in Diabetes Mellitus and Its Complications

Diabetes mellitus (DM) and its related complications are among the leading causes of disability and mortality worldwide. Substantial studies have explored epigenetic regulation that is involved in the modifications of DNA and proteins, but RNA modifications in diabetes are still poorly investigated. In recent years, posttranscriptional epigenetic modification of RNA (the so-called 'epitranscriptome') has emerged as an interesting field of research. Numerous modifications, mainly N⁶ -methyladenosine (m⁶A), have been identified in nearly all types of RNAs and have been demonstrated to have an indispensable effect in a variety of human diseases, such as cancer, obesity, and diabetes. Therefore, it is particularly important to understand the molecular basis of RNA modifications, which might provide a new perspective for the pathogenesis of diabetes mellitus and the discovery of new therapeutic targets. In this review, we aim to summarize the recent progress in the epitranscriptomics involved in diabetes and diabetes-related complications. We hope to provide some insights for enriching the understanding of the epitranscriptomic regulatory mechanisms of this disease as well as the development of novel therapeutic targets for future clinical benefit.

Artesunate inhibits the development of PVR by suppressing the TGF-β/Smad signaling pathway

Proliferative vitreoretinopathy (PVR) is the main cause of retinal detachment surgery failure. The epithelial-mesenchymal transition (EMT) induced by transforming growth factor (TGF-β2) plays an important role in the development of PVR. Artesunate has been widely studied as a treatment for ophthalmic diseases because of its antioxidant, anti-inflammatory, antiapoptotic and antiproliferative properties. The purpose of this study was to investigate the effects of artesunate on the TGF-β2-induced EMT in ARPE-19 cells and PVR development. We found that artesunate inhibited the proliferation and contraction of ARPE-19 cells after the EMT and the autocrine effects of TGF-β2 on ARPE-19 cells. Additionally, the levels of Smad3 and p-Smad3 were increased in clinical samples, and artesunate decreased the levels of Smad3 and p-Smad3 in ARPE-19 cells treated with TGF-β2. Artesunate also inhibited the occurrence and development of PVR in vivo. In summary, artesunate inhibits the occurrence and development of PVR by inhibiting the EMT in ARPE-19 cells.

MTDH associates with m6A RNA methylation and predicts cancer response for immune checkpoint treatment

Immune checkpoint blockade (ICB) persistently provides a prognosis improvement but only in a small fraction of patients with cancer due to immunotherapy resistance induced by the consecutive activated oncogenic pathways, including MAPK, Akt, and WNT pathway partially driven by Metadherin (MTDH). However, there is no study to investigate the potential role and mechanisms of MTDH in ICB-treated cancers. Here, we systematically explored the cohorts from The Cancer Genome Atlas (TCGA) and independent cancer cohorts. Elevated MTDH expression was founded to associate with a worse overall survival and poorer immune response in patients with cancer. Dysregulated tumor-infiltrating immune cells and inhibitory immune checkpoint expression were correlated with MTDH expression. Furthermore, the mutual interactions between epithelial-to-mesenchymal-transition, m6A-RNA-methylation, and MTDH may illustrate the potential mechanisms of MTDH resistant to ICB treatment. Although more designed experiments and trials are needed in the future, targeting MTDH may help to overcome immunotherapy resistance in a wide range of cancers.

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MTDH associates with prognosis and immunotherapy response for patients with cancer

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MTDH associates with dysregulated tumor immune environment and checkpoint expression

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The MTDH/m6A RNA methylation/EMT pathway may contribute to immunotherapy resistance

The role of N6-methyladenosine (m6A) in eye diseases

N6-methyladenosine (m6A) is the most common form of internal RNA modification in eukaryotes. The dynamic regulation of m6A modification mainly rely on three proteases, installed by m6A methyltransferase, removed by m6A demethylase and recognized by m6A reader protein, which regulates the metabolism of RNA, thereby regulating the processes of cell proliferation, migration, invasion and apoptosis. Recently, a number of studies have found that m6A aberrant methylation in some eye diseases. This review was to summarize the recent research progress on the role of m6A modification in eye diseases and give a perspective on its prospective applications in eye diseases.

Expression of lncRNA TINCR in the placenta of patients with pre-eclampsia and its effect on the biological behaviours of trophoblasts

To explore the effect of lncRNA TINCR on the biological behaviours of trophoblasts, we detected and analyzed the expression of terminal differentiation-induced non-protein coding RNA (TINCR) in the placenta tissues of pre-eclamptic and non-pre-eclamptic pregnant women. The gain- and loss-of-function of TINCR was performed to examine the proliferation, migration and invasion abilities of Htr-8/Svneo cells. The levels of epithelial-mesenchymal transition (EMT)-related proteins, cyclin and Wnt/β-catenin pathway were detected. High expression of lncRNA TINCR appeared in placental tissues of patients with pre-eclampsia. The proliferation, invasion and migration of Htr-8/Svneo cells were promoted by TINCR downregulation; the cells were transited from G0/G1 to S phase; and EMT was promoted and the Wnt/β-catenin pathway was activated. In summary, the downregulation of lncRNA TINCR activated the Wnt/β-catenin pathway and promoted the proliferation, invasion and migration of Htr-8/Svneo cells. This study may provide a theoretical basis for treatment of patients with pre-eclampsia.

METTL3 attenuates proliferative vitreoretinopathy and epithelial-mesenchymal transition of retinal pigment epithelial cells via wnt/β-catenin pathway

Proliferative vitreoretinopathy (PVR) is a refractory vitreoretinal fibrosis disease, and epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is the key pathological mechanism of PVR. However, few studies focused on the role of METTL3, the dominating methyltransferase for m6A RNA modification in PVR pathogenesis. Immunofluorescence staining and qRT-PCR were used to determine the expression of METTL3 in human tissues. Lentiviral transfection was used to stably overexpress and knockdown METTL3 in ARPE-19 cells. MTT assay was employed to study the effects of METTL3 on cell proliferation. The impact of METTL3 on the EMT of ARPE-19 cells was assessed by migratory assay, morphological observation and expression of EMT markers. Intravitreal injection of cells overexpressing METTL3 was used to assess the impact of METTL3 on the establishment of the PVR model. We found that METTL3 expression was less in human PVR membranes than in the normal RPE layers. In ARPE-19 cells, total m6A abundance and the METTL3 expression were down-regulated after EMT. Additionally, METTL3 overexpression inhibited cell proliferation through inducing cell cycle arrest at G0/G1 phase. Furthermore, METTL3 overexpression weakened the capacity of TGFβ1 to trigger EMT by regulating wnt/β -catenin pathway. Oppositely, knockdown of METTL3 facilitated proliferation and EMT of ARPE-19 cells. In vivo, intravitreal injection of METTL3-overexpressing cells delayed the development of PVR compared with injection of control cells. In summary, this study suggested that METTL3 is involved in the PVR process, and METTL3 overexpression inhibits the EMT of ARPE-19 cells in vitro and suppresses the PVR process in vivo.