Cardiac
fibrosis is a common pathological manifestation in multiple
cardiovascular diseases and often results in myocardial stiffness and cardiac dysfunctions.
LncRNA (
long noncoding RNA) participates in a number of pathophysiological processes. However, its role in cardiac
fibrosis remains unclear. The purpose of this study was to investigate the role and molecular mechanism of MetBil in regulating cardiac
fibrosis. Our data showed that METTL3 binding
lncRNA (MetBil) was significantly increased both in fibrotic tissue following
myocardial infarction (MI) in mice and in cardiac fibroblasts (CFs) exposed to TGF-β1 (20 ng/mL) or 20% FBS. Overexpression of MetBil augmented
collagen deposition, CF proliferation and activation while silencing MetBil exhibited the opposite effects. Importantly, heterozygous knockout of MetBil alleviated cardiac
fibrosis and improved cardiac function after MI.
RNA pull-down and
RNA-binding protein immunoprecipitation assay showed that METTL3 is a direct downstream target of MetBil; consistently, MetBil and METTL3 were co-localized in both the nucleus and cytoplasm of CFs. Interestingly, MetBil regulated METTL3 expression at
protein level, but not
mRNA level, in
ubiquitin-
proteasome pathway. Enforced expression of METTL3 canceled the antifibrotic effects of silencing MetBil reflected by increased
collagen production, CF proliferation and activation. Most notably, the m6A-modified
fibrosis-regulated genes mediated by METTL3 are profoundly involved in the regulation of MetBil in the cardiac
fibrosis following MI. Our study reveals that MetBil as a novel regulator of
fibrosis promotes cardiac
fibrosis via interacting with METTL3 and regulating the expression of the methylated
fibrosis-associated genes, providing a new intervening target for
fibrosis-associated
cardiac diseases.