METTL3-Mediated m6A Regulation of CircINTS4/miR-146b-3p Axis in Rheumatoid Arthritis.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by synovial inflammation and joint destruction. Despite advances in understanding its pathogenesis, the role of epigenetic regulation and non-coding RNA networks remains inadequately explored. This study investigates the involvement of N6-methyladenosine (m6A) modification and circular RNA (circRNA), specifically circINTS4, in RA. METHODS: We conducted a bibliometric analysis to map research trends in m6A and miR-146 family studies in RA. Whole-transcriptome sequencing was performed on synovial tissue from RA patients and healthy controls (HCs) to identify differentially expressed circRNAs. miRNA expression was profiled using publicly available datasets. The role of METTL3 in regulating circINTS4 was examined through loss-of-function experiments in RA fibroblast-like synoviocytes (RA-FLS). A dual-luciferase reporter assay validated the direct interaction between circINTS4 and miR-146b-3p. Functional assays in RA-FLS and in vivo models assessed the impact of circINTS4 depletion on disease progression. RESULTS: circINTS4 was the most significantly downregulated circRNA in RA, and miR-146b-3p was the most upregulated miRNA in RA patients. METTL3 depletion in RA-FLS reduced global m6A methylation and decreased m6A enrichment on circINTS4, leading to increased circINTS4 expression and decreased miR-146b-3p levels. Clinical analysis revealed an inverse relationship between circINTS4 and miR-146b-3p expression. Functionally, circINTS4 served as a sponge for miR-146b-3p, with its depletion enhancing RA-FLS proliferation, migration, and resistance to apoptosis. In vivo, circINTS4 knockdown exacerbated synovial inflammation and elevated pro-inflammatory cytokine levels in a rat model of RA. CONCLUSION: Our findings reveal that METTL3-mediated m6A modification regulates the circINTS4/miR-146b-3p axis, modulating RA-FLS pathogenicity and inflammatory responses. CircINTS4 acts as a molecular sponge for miR-146b-3p and serves as a promising biomarker for RA disease severity. This study provides new insights into the role of m6A methylation and circRNA-miRNA networks in RA, highlighting their potential as diagnostic and therapeutic targets.