Inhibition of miR-154 Protects Against Cardiac Dysfunction and Fibrosis in a Mouse Model of Pressure Overload.

Expression of miR-154 is upregulated in the diseased heart and was previously shown to be upregulated in the lungs of patients with pulmonary fibrosis. However, the role of miR-154 in a model of sustained pressure overload-induced cardiac hypertrophy and fibrosis had not been assessed. To examine the role of miR-154 in the diseased heart, adult male mice were subjected to transverse aortic constriction for four weeks, and echocardiography was performed to confirm left ventricular hypertrophy and cardiac dysfunction. Mice were then subcutaneously administered a locked nucleic acid antimiR-154 or control over three consecutive days (25 mg/kg/day) and cardiac function was assessed 8 weeks later. Here, we demonstrate that therapeutic inhibition of miR-154 in mice with pathological hypertrophy was able to protect against cardiac dysfunction and attenuate adverse cardiac remodelling. The improved cardiac phenotype was associated with attenuation of heart and cardiomyocyte size, less cardiac fibrosis, lower expression of atrial and B-type natriuretic peptide genes, attenuation of profibrotic markers, and increased expression of p15 (a miR-154 target and cell cycle inhibitor). In summary, this study suggests that miR-154 may represent a novel target for the treatment of cardiac pathologies associated with cardiac fibrosis, hypertrophy and dysfunction.

MicroRNAs differentially regulated in cardiac and skeletal muscle in health and disease: potential drug targets?

The identification of non-coding RNA species, previously thought of as 'junk' DNA, adds a new dimension of complexity to the regulation of DNA, RNA and protein. MicroRNAs are short non-coding RNA species that control gene expression, are dysregulated in settings of cardiac and skeletal muscle disease and have emerged as promising therapeutic targets. MicroRNAs specifically enriched in cardiac and skeletal muscle are called myomiRs and play an important role in cardiac pathology and skeletal muscle biology. Moreover, microRNA profiles are altered in response to exercise and disease; thus, their potential as therapeutic drug targets is being widely explored. In the cardiovascular field, therapeutic inhibition of microRNAs has been shown to be effective in improving cardiac outcome in preclinical cardiac disease models. MicroRNAs that promote skeletal muscle regeneration are attractive therapeutic targets in muscle wasting conditions where regenerative capacity is compromised.

Therapeutic silencing of miR-652 restores heart function and attenuates adverse remodeling in a setting of established pathological hypertrophy.

Expression of microRNA-652 (miR-652) increases in the diseased heart, decreases in a setting of cardioprotection, and is inversely correlated with heart function. The aim of this study was to assess the therapeutic potential of inhibiting miR-652 in a mouse model with established pathological hypertrophy and cardiac dysfunction due to pressure overload. Mice were subjected to a sham operation or transverse aortic constriction (TAC) for 4 wk to induce hypertrophy and cardiac dysfunction, followed by administration of a locked nucleic acid (LNA)-antimiR-652 (miR-652 inhibitor) or LNA control. Cardiac function was assessed before and 8 wk post-treatment. Expression of miR-652 increased in hearts subjected to TAC compared to sham surgery (2.9-fold), and this was suppressed by ∼95% in LNA-antimiR-652-treated TAC mice. Inhibition of miR-652 improved cardiac function in TAC mice (fractional shortening:29±1% at 4 wk post-TAC compared to 35±1% post-treatment) and attenuated cardiac hypertrophy. Improvement in heart function was associated with reduced cardiac fibrosis, less apoptosis and B-type natriuretic peptide gene expression, and preserved angiogenesis. Mechanistically, we identified Jagged1 (a Notch1 ligand) as a novel direct target of miR-652. In summary, these studies provide the first evidence that silencing of miR-652 protects the heart against pathological remodeling and improves heart function.