Novel Insights Into the Multifaceted Functions of RNA n6-Methyladenosine Modification in Degenerative Musculoskeletal Diseases

Novel Insights into the Links between N6-Methyladenosine and Regulated Cell Death in Musculoskeletal Diseases

Musculoskeletal diseases (MSDs), including osteoarthritis (OA), osteosarcoma (OS), multiple myeloma (MM), intervertebral disc degeneration (IDD), osteoporosis (OP), and rheumatoid arthritis (RA), present noteworthy obstacles associated with pain, disability, and impaired quality of life on a global scale. In recent years, it has become increasingly apparent that N6-methyladenosine (m6A) is a key regulator in the expression of genes in a multitude of biological processes. m6A is composed of 0.1-0.4% adenylate residues, especially at the beginning of 3'-UTR near the translation stop codon. The m6A regulator can be classified into three types, namely the "writer", "reader", and "eraser". Studies have shown that the epigenetic modulation of m6A influences mRNA processing, nuclear export, translation, and splicing. Regulated cell death (RCD) is the autonomous and orderly death of cells under genetic control to maintain the stability of the internal environment. Moreover, distorted RCDs are widely used to influence the course of various diseases and receiving increasing attention from researchers. In the past few years, increasing evidence has indicated that m6A can regulate gene expression and thus influence different RCD processes, which has a central role in the etiology and evolution of MSDs. The RCDs currently confirmed to be associated with m6A are autophagy-dependent cell death, apoptosis, necroptosis, pyroptosis, ferroptosis, immunogenic cell death, NETotic cell death and oxeiptosis. The m6A-RCD axis can regulate the inflammatory response in chondrocytes and the invasive and migratory of MM cells to bone remodeling capacity, thereby influencing the development of MSDs. This review gives a complete overview of the regulatory functions on the m6A-RCD axis across muscle, bone, and cartilage. In addition, we also discuss recent advances in the control of RCD by m6A-targeted factors and explore the clinical application prospects of therapies targeting the m6A-RCD in MSD prevention and treatment. These may provide new ideas and directions for understanding the pathophysiological mechanism of MSDs and the clinical prevention and treatment of these diseases.

METTL3 potentiates osteogenic differentiation of bone marrow mesenchymal stem cells via IGF2BP1/m6A/RUNX2

OBJECTIVE

Maxillofacial bone defect is a critical obstacle for maxillofacial tumors and periodontal diseases. The osteogenic differentiation of bone marrow mesenchymal stem cells BMSCs is critical for maxillofacial osteogenesis and functional reconstruction. Here, our study focused on the functions and mechanism of N6-methyladenosine during BMSCs osteogenic differentiation BMSCs.

SUBJECT AND METHODS

Biofunctions of BMSCs were detected using ALP activity and alizarin red S staining assays. The molecular interaction within RNA/protein was identified by RNA immunoprecipitation and/or methylation immunoprecipitation.

RESULTS

Results indicated that m6A 'writer' METTL3 upregulated during the osteogenic differentiation of BMSCs upon osteogenic induction. Functionally, assays' results revealed that METTL3 overexpression promoted the osteogenic differentiation of BMSC, while METTL3 knockdown repressed the osteogenic differentiation. Mechanistically, results revealed that RUNX2 mRNA was a m6A-methylated target by METTL3 at its 3'-UTR. Moreover, m6A reader IGF2BP1 recognized the m6A site on RUNX2 mRNA to enhance its stability.

CONCLUSION

In conclusion, our findings revealed the novel roles of METTL3 in BMSCs osteogenic differentiation via the IGF2BP1/m6A/RUNX2 signaling axis of m6A-dependent manner, providing a potential therapeutic target for maxillofacial bone defects treatment.

Novel insights of EZH2-mediated epigenetic modifications in degenerative musculoskeletal diseases

Degenerative musculoskeletal diseases (Osteoporosis, Osteoarthritis, Degenerative Spinal Disease and Sarcopenia) are pathological conditions that affect the function and pain of tissues such as bone, cartilage, and muscles, and are closely associated with ageing and long-term degeneration. Enhancer of zeste homolog 2 (EZH2), an important epigenetic regulator, regulates gene expression mainly through the PRC2-dependent trimethylation of histone H3 at lysine 27 (H3K27me3). Increasing evidence suggests that EZH2 is involved in several biological processes closely related to degenerative musculoskeletal diseases, such as osteogenic-adipogenic differentiation of bone marrow mesenchymal stem cells, osteoclast activation, chondrocyte functional status, and satellite cell proliferation and differentiation, mainly through epigenetic regulation (H3K27me3). Therefore, the synthesis and elucidation of the role of EZH2 in degenerative musculoskeletal diseases have attracted increasing attention. In addition, although EZH2 inhibitors have been approved for clinical use, whether they can be repurposed for the treatment of degenerative musculoskeletal diseases needs to be considered. Here, we reviewed the role of EZH2 in the development of degenerative musculoskeletal diseases and brought forward prospects of its pharmacological inhibitors in the improvement of the treatment of the diseases.

N6-methyladenosine (m6A) writer METTL3 accelerates the apoptosis of vascular endothelial cells in high glucose

Recent studies have shown that N⁶-methyladenosine (m⁶A) methylation, one of the most prevalent epigenetic modifications, is involved in diabetes mellitus. However, whether m⁶A regulates diabetic vascular endothelium injury is still elusive. Present research aimed to investigate the regulation and mechanism of m⁶A on vascular endothelium injury. Upregulation of METTL3 was observed in the high glucose (HG)-induced human umbilical vein endothelial cells (HUVECs), following with the upregulation of m⁶A methylation level. Functionally, METTL3 silencing repressed the apoptosis and recovered the proliferation of HUVECs disposed by HG. Moreover, HG exposure upregulated the expression of suppressor of cytokine signaling3 (SOCS3). Mechanistically, METTL3 targeted the m⁶A site on SOCS3 mRNA, which positively regulated the mRNA stability of SOCS3. In conclusion, METTL3 silencing attenuated the HG-induced vascular endothelium cells injury via promoting SOCS3 stability. In conclusion, this research expands the understanding of m⁶A on vasculopathy in diabetes mellitus and provides a potential strategy for the protection of vascular endothelial injury.

N6-methyladenosine (m6A) reader IGF2BP1 facilitates clear-cell renal cell carcinoma aerobic glycolysis

Emerging articles have reported that N⁶-methyladenosine (m⁶A) modification is mainly involved in clear-cell renal cell carcinoma (ccRCC) tumorigenesis. However, the regulatory mechanisms of m⁶A reader IGF2BP1 involved in ccRCC tumor energy metabolism are currently unknown. Results showed that the m⁶A reader IGF2BP1 exhibited significantly higher expression in ccRCC cells. Functionally, results by gain/loss functional assays indicated that IGF2BP1 promoted the glycolytic characteristics, including glucose uptake, lactate production and extracellular acidification rate (ECAR). Mechanistically, IGF2BP1 recognized the m⁶A modified sites on LDHA mRNA and enhanced its mRNA stability, thereby accelerating tumor energy metabolism. Thus, our work reveals a novel facet of the m⁶A that promoted mRNA stability and highlighted the functional importance of IGF2BP1 as m⁶A readers in post-transcriptional gene regulation.

m6A-modified circFOXK2 targets GLUT1 to accelerate oral squamous cell carcinoma aerobic glycolysis

N⁶-methyladenosine (m⁶A) is an abundant nucleotide modification in mRNA, and its emerging roles have been gradually identified. However, the potential function of m⁶A and m⁶A-modified circular RNA (circRNA) is still unclear. Here, m⁶A-circRNA epitranscriptomic microarray analysis revealed a high-expressed m⁶A-modified circFOXK2 (hsa_circ_0000816, from FOXK2 gene) in oral squamous cell carcinoma (OSCC). For the biofunctions of OSCC, results revealed that circFOXK2 promoted the malignant phenotypes of OSCC cells. Methylated RNA immunoprecipitation sequencing (MeRIP-Seq) demonstrated that a remarkable m⁶A modified site was installed on glucose transporter 1 (GLUT1) mRNA. Mechanistically, circFOXK2 promoted the GLUT1 mRNA stability through cooperating with insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) in a m⁶A-dependent manner. In summary, the present study explored the oncogenic role of m⁶A-modified circFOXK2 in OSCC through the m⁶A-dependent IGF2BP3/GLUT1 axis, indicating a potential therapeutic target for OSCC.

Characterization of immune microenvironment infiltration and m6A regulator-mediated RNA methylation modification patterns in osteoarthritis

Background

Few studies have been reported the potential role of N6-methyladenosine (m6A) modification in osteoarthritis (OA). We investigated the patterns of m6A modification in the immune microenvironment of OA.

Methods

We evaluated the m6A modification patterns based on 22 m6A regulators in 139 OA samples and systematically associated these modification patterns with immune cell infiltration characteristics. The function of m6A phenotype-related differentially expressed genes (DEGs) was investigated using gene enrichment analysis. An m6A score model was constructed using principal component analysis (PCA), and an OA prediction model was established based on the key m6A regulators. We used real-time PCR analysis to detect the changes of gene expression in the cell model of OA.

Results

Healthy and OA samples showed significant differences in the expression of m6A regulators. Nine key m6A regulators, two m6A modification patterns, m6A-related genes and two gene clusters were identified. Some m6A regulators had a strong correlation with each other. Gene clusters and m6A clusters have high similarity, and cluster A corresponds to a high m6A score. Immunocytes infiltration differed significantly between the two clusters, with the m6A cluster B and gene cluster B having more types of infiltrating immunocytes than cluster A. The predictive model can also predict the progression of OA through m6A regulators expression. The results of real-time PCR analysis showed that the gene expression in the cell model of OA is similar to that of the m6A cluster B.

Conclusions

Our study reveals for the first time the potential regulatory mechanism of m6A modification in the immune microenvironment of OA. This study also sheds new light on the pathogenesis of OA.

The emerging roles of N6-methyladenosine in osteoarthritis

Finding new biomarkers and molecular targets to guide OA treatment remains a significant challenge. One of the most frequent forms of RNA methylation, N6-methyladenosine (m6A), can affect gene expression and RNA transcription, processing, translation, and metabolism. Osteoarthritis (OA) can cause disability and pain degenerative disease, reduce the quality of life of the elderly, and increase the social and economic burden. Changes in m6A levels are crucial in OA progress. In this review, the discussion will concentrate on the role that m6A plays in OA occurrence and progression. The m6A involved in the OA process mainly includes METTL3 and FTO. Current studies on m6A and OA primarily focus on four signaling pathways, namely, NF-κB, LNCRNAs, ATG7, and Bcl2. m6A participates in these signaling pathways and affects cellular inflammation, apoptosis, senescence, and autophagy, thus controlling the OA process. The modification of m6A affects so many signaling pathways. For the treatment of OA, it may represent a viable new therapeutic target.

Regulatory Role of N6-Methyladenosine (m6A) Modification in Osteoarthritis

Osteoarthritis (OA) is the most common joint disease, usually occurring in middle-aged and elderly people. However, current treatment for OA in its early stages is ineffective, and drug therapy is often ineffective in slowing the progression of the disease. In fact, a deeper understanding of the underlying molecular mechanisms of OA could help us to better develop effective therapeutic measures. N6-methyladenosine (m6A) is a methylation that occurs at the adenosine N6-position, which is the most common internal modification on eukaryotic mRNAs. The role and mechanisms of m6A in mammalian gene regulation have been extensively studied. The “Writer”, “eraser”, and “reader” proteins are key proteins involved in the dynamic regulation of m6A modifications. Recent studies on post-transcriptional regulation alone have shown that m6a modification has an important role in the development of OA. This paper summarizes the specific regulatory processes of M6A in disease and reviews the role of m6A in OA, describing its pathophysiological role and molecular mechanisms, as well as its future research trends and potential clinical applications in OA.

N6-methyladenosine (m6A) reader IGF2BP2 stabilizes HK2 stability to accelerate the Warburg effect of oral squamous cell carcinoma progression

PURPOSE

The N⁶-methyladenosine (m⁶A) has been involved in the regulation of cell proliferation and metastasis in multiple cancers. However, the biological significance of m⁶A reader IGF2BP2 in oral squamous cell carcinoma (OSCC) and the mechanism of IGF2BP2 itself have not been fully investigated.

METHODS

The cellular phenotypes of OSCC cells were determined by CCK-8 and transwell migration assays. The energy metabolism was detected using glucose uptake/lactate production assay and extracellular acidification rate analysis. The molecular interaction was tested by  RNA immunoprecipitation  assay.

RESULTS

Here, results indicated that IGF2BP2 was up-regulated in OSCC and that it acted as a predictor of poor prognosis. IGF2BP2 promoted the proliferation, migration and Warburg effect of OSCC cells in vitro. Mechanistical assays illustrated that IGF2BP2 directly interacted with HK2 mRNA by binding the 3'-UTR m⁶A site. Moreover, IGF2BP2 positively promoted the stability of HK2 mRNA and thus the protein level of HK2 increased upon IGF2BP2 overexpression.

CONCLUSIONS

In conclusion, the IGF2BP2/m⁶A/HK2 axis accelerated the abnormal energy metabolism of OSCC. Taken together, these findings revealed a novel mechanism by which IGF2BP2 functions in OSCC progression, which may provide new therapy options for OSCC patients.

SIAH1 promotes senescence and apoptosis of nucleus pulposus cells to exacerbate disc degeneration through ubiquitinating XIAP

BACKGROUND

Using clinical samples and database analysis, this study aimed to investigate the signaling pathways that mediated degeneration of nucleus pulposus cells (NPCs) in patients with intervertebral disc degeneration (IDD).

METHODS

NPCs were extracted from enucleated intervertebral discs of IDD patients, and the senescence, apoptosis, and extracellular matrix (ECM) synthesis levels of cells were confirmed by β-galactosidase (SA-β-gal), Western blot, and measurement of superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione (GSH). The microarray expression profile of GSE56081 was downloaded to screen differentially expressed mRNAs. CO-IP and ubiquitination assays were used to determine the targeted regulation of XIAP by SIAH1. Methylation of mRNA was verified by m6A RIP and actinomycin D assays.

RESULTS

NPCs extracted from the enucleated intervertebral discs of IDD patients exhibited marked senescence, apoptosis, elevated levels of inflammation, and decreased ECM synthesis. The expression of SIAH1 was significantly elevated in NPCs of IDD patients, and SIAH1 knockdown reversed senescence, apoptosis, elevated levels of inflammation, and decreased ECM synthesis in NPCs of IDD patients. CO-IP and ubiquitination assays indicated that SIAH1 can target and ubiquitinate XIAP. Besides, MeRIP-qPCR and actinomycin experiments showed that METTL3-mediated m6A can methylate SIAH1 mRNA.

CONCLUSION

In IDD patients, SIAH1 can target and ubiquitinate XIAP, thereby mediating senescence, apoptosis, increased inflammation, and decreased ECM synthesis of NPCs, while METTL3-mediated m6A can methylate SIAH1 mRNA, producing harmful effects.