Role and mechanism of METTL3 in fibrosis-associated signaling in CVB3-infected H9c2 cardiomyocytes through the lncRNA MEG3/c-MYC/SMAD2 axis

Viral myocarditis (VMC) is an inflammatory disease of the heart muscle caused by viral infection and may lead to myocardial fibrosis. This study aims to investigate the role of METTL3 in myocardial fibrosis in VMC. METTL3 expression was intervened with in VMC cell models, followed by measurement of LDH, CK-MB, and TGF-β1. The expression of METTL3, lncRNA MEG3, c-MYC, SMAD2, Collagen I, Collagen III, and α-SMA was detected by RT-qPCR and Western blot. α-SMA expression was observed by immunofluorescence. MeRIP-qPCR was used to detect m6A levels of MEG3. RNA stability experiments were conducted to determine the residual level of MEG3. The bindings of lncRNA MEG3 to c-MYC and c-MYC to the SMAD2 promoter were analyzed. Results showed that METTL3, c-MYC, and SMAD2 were highly expressed in VMC cell models. METTL3 inhibition increased cell viability and reduced LDH, CK-MB, TGF-β1, Collagen I, Collagen III, and α-SMA. METTL3-mediated m6A modification promoted MEG3 expression, and MEG3 bound to c-MYC and enhanced SMAD2 expression. Overexpression of MEG3 or SMAD2 partially reversed the inhibitory effect of METTL3 on fibrotic-like changes of myocardial cells. In conclusion, METTL3 promotes fibrotic-like changes of myocardial cells in VMC cell models through the lncRNA MEG3/c-MYC/SMAD2 axis via m6A modification.