39 m6A-mediated epitranscriptional reprogramming drives cardiac fibrosis by suppressing PGC-1α and boosting mitochondrial fission

Dysregulated mitochondrial fission drives pathological cell states in cardiac fibrosis, but its upstream regulatory mechanisms remain poorly understood. The role of epitranscriptomic regulation, particularly N6-methyladenosine (m6A) modification, in this process has not been defined. We employed integrated approaches including in vitro models of TGF-β1-stimulated cardiac fibroblasts, in vivo mouse models of isoproterenol-induced cardiac fibrosis, and analysis of human atrial fibrillation tissues. Techniques encompassed molecular profiling, m6A-specific assays (MeRIP-qPCR, RIP-qPCR), functional studies, high-resolution imaging, and fibroblast-targeted AAV9-mediated gene manipulation. METTL3 and YTHDF2 were significantly upregulated in experimental and human fibrotic hearts. METTL3-mediated m6A modification of PGC-1α mRNA promoted its recognition and degradation by YTHDF2. This suppression of PGC-1α led to excessive Drp1-dependent mitochondrial fission, which in turn promoted cardiac fibroblast proliferation, migration, and extracellular matrix production. Inhibition of METTL3 or YTHDF2 restored PGC-1α expression, normalized mitochondrial dynamics, and attenuated fibrotic responses in vitro. Fibroblast-specific knockdown of METTL3 or YTHDF2 in vivo attenuated fibrosis, improved mitochondrial ultrastructure, and restored systolic function. In human atrial fibrillation tissue, activation of this axis was associated with reduced PGC-1α expression, enhanced mitochondrial fission, and greater disease severity. Our findings identify a novel epitranscriptomic pathway in which METTL3 and YTHDF2 regulate PGC-1α through m6A modification. Targeting this axis may represent a potential therapeutic strategy for cardiac fibrosis, providing insight into the molecular mechanisms underlying fibrotic remodeling. The proposed mechanism is summarised in figure 1.