MicroRNAs in the Human Heart

TLDR

Chronic heart failure involves left ventricular remodeling and reactivation of a fetal gene program, mechanisms of which remain incompletely understood. The study aims to demonstrate that cardiac microRNAs contribute to the transcriptional changes observed in heart failure. Cardiac transcriptome analyses revealed fetal‑like patterns in failing hearts, and transfection of cardiomyocytes with fetal microRNAs induced hypertrophy and gene expression changes resembling heart failure. MicroRNA profiling showed profound alterations that mirror fetal expression, bioinformatics linked these changes to mRNA binding sites, and functional assays confirmed that fetal microRNAs drive hypertrophy and gene expression shifts, underscoring their role in heart failure.

Abstract

Background— Chronic heart failure is characterized by left ventricular remodeling and reactivation of a fetal gene program; the underlying mechanisms are only partly understood. Here we provide evidence that cardiac microRNAs, recently discovered key regulators of gene expression, contribute to the transcriptional changes observed in heart failure. Methods and Results— Cardiac transcriptome analyses revealed striking similarities between fetal and failing human heart tissue. Using microRNA arrays, we discovered profound alterations of microRNA expression in failing hearts. These changes closely mimicked the microRNA expression pattern observed in fetal cardiac tissue. Bioinformatic analysis demonstrated a striking concordance between regulated messenger RNA expression in heart failure and the presence of microRNA binding sites in the respective 3′ untranslated regions. Messenger RNAs upregulated in the failing heart contained preferentially binding sites for downregulated microRNAs and vice versa. Mechanistically, transfection of cardiomyocytes with a set of fetal microRNAs induced cellular hypertrophy as well as changes in gene expression comparable to the failing heart. Conclusions— Our data support a novel mode of regulation for the transcriptional changes in cardiac failure. Reactivation of a fetal microRNA program substantially contributes to alterations of gene expression in the failing human heart.