Abstract 14608: Functional Screening Identifies Micrornas Inducing Cardiac Regeneration
In mammals, embryonic development of the heart depends on the increase in cardiomyocyte number, but shortly after birth cardiac myocytes stop proliferating and further growth of the myocardium occurs through hypertrophy of existing cardiomyocytes. The actual capacity of the mammalian heart to regenerate following injury is controversial. Several microRNAs - evolutionarily conserved small noncoding RNAs that regulate gene expression - have been implicated in different aspects of heart function and dysfunction, though only a few of them have been shown to control of cardiomyocyte proliferation, all exerting a negative role. Here, we assessed the hypothesis that microRNAs may actively control cardiomyocyte proliferation in heart development and disease. We performed a high-content, fluorescence microscopy-based high-throughput screening in rat neonatal cardiomyocytes using a library of microRNA mimics corresponding to all the annotated microRNAs (∼1000 microRNAs). Proliferation was assessed combining different read-outs: EdU incorporation, Ki-67 expression, histone H3 phosphorylation and AuroraB-kinase localization to mid-bodies. The best candidates were tested in vivo by both injecting the synthetic microRNA intracardially into the heart of newborn rats (n=10) and by delivering their coding sequence using AAV9 vectors intraperitoneally into neonatal mice (n=10) and into the infarct border zone after ligation of the coronary artery in adult mice (n=30), followed by histological, morphological and echocardiographic analysis. We identified 38 microRNAs able to increase cardiomyocyte proliferation by at least 3-fold. Two of these microRNAs also induced proliferation of cardiomyocytes in normal hearts (0.15±0.02 and 0.80±0.08 EdU+ cells in miRNA-expressing and control hearts) and after myocardial infarction, resulting in significantly reduced scar size (14.2±1.5% and 27±2% of the left ventricle) and improved cardiac function (ejection function at 60 days: 59±2% and 38±6% in miRNA-expressing and control hearts). In conclusion, the induction of cardiomyocyte proliferation in vivo by modulation of specific microRNAs might prompt the development of novel, exciting therapies against ischemic cardiomyopathy and heart failure.
- Regenerative medicine stem cells
- Gene therapy
- Myocardial infarction
- Cardiovascular therapeutics
- © 2012 by American Heart Association, Inc.