Abstract Objective Myocardial ischemia-reperfusion (I/R) injury remains a major contributor to cardiac morbidity and mortality, and accumulating evidence suggests that epitranscriptomic regulation may critically influence cardiac stress responses. N6-methyladenosine (m6A) modification and circular RNAs (circRNAs) have emerged as important regulators of cardiovascular pathology; however, their integrated roles in myocardial I/R injury, particularly under chronic cold stress, remain poorly defined. Methods A mouse model of myocardial I/R injury was established under room-temperature or chronic cold exposure conditions. Cardiac function, infarct size, histopathology, and serum injury markers were assessed. Global m6A levels were quantified, and m6A-modified circRNA profiles were analyzed using epitranscriptomic microarrays and bioinformatics approaches. Differentially expressed circRNAs were validated in vivo and in hypoxia-reoxygenation-treated neonatal cardiomyocytes. Circular structures and stability were confirmed by Sanger sequencing, divergent/ convergent PCR, and actinomycin D assays. Competing endogenous RNA (ceRNA) networks were constructed to identify downstream regulatory pathways. Results Myocardial I/R injury resulted in significant cardiac dysfunction, increased infarct size, histological damage, and elevated serum CK-MB and LDH levels, accompanied by a marked increase in global m6A methylation. Epitranscriptomic profiling identified 391 circRNAs with altered m6A modification following I/R injury, involving pathways related to molecular binding, cellular processes, and kinase signaling. Multiple circRNAs exhibited consistent dysregulation in both in vivo and in vitro I/R models and displayed high structural stability. Importantly, chronic cold exposure significantly exacerbated I/R-induced cardiac dysfunction and infarct severity while further modulating the expression of specific m6A-modified circRNAs. ceRNA network analysis revealed that cold-responsive circRNAs potentially regulate myocardial injury through miRNA-mediated signaling pathways. Conclusion This study identifies m6A-modified circRNAs as key epitranscriptomic regulators of myocardial I/R injury and demonstrates that chronic cold stress amplifies circRNA-mediated regulatory networks. These findings provide novel mechanistic insight into temperature-dependent epigenetic regulation in ischemic heart disease and highlight m6A-circRNAs as potential therapeutic targets.
Wu et al. (Sat,) studied this question.