Young Investigator Award Session - Heart40Targeting the miRNA-106b-25 cluster as a potential regenerative therapeutic approach for myocardial injury41An allogeneic bioengineered myocardial graft limits infarct size and improves cardiac function: pre-clinical study in the porcine myocardial infarction model42Phosphoinositide 3-kinase gamma inhibition protects against anthracycline-induced cardiomyopathy by boosting cardiac autophagy43Functional screening of microRNAs identifies miR-22 as a …
Authors: E Dirkx, I Perea Gil, MC Li, S K Gupta, THM Nguyen, F Syeda, E Dirkx, A Raso, L Braga, L Zentilin, S Zacchigna, M Giacca, LJ De Windt, C Prat-Vidal, C Galvez-Monton, S Roura, A Llucia-Valldeperas, C Soler-Botija, I Diaz-Guemes, V Crisostomo, FM Sanchez-Margallo, A Bayes-Genis, J Cimino, MC De Santis, N Pianca, S Sciarretta, M Sandri, T Zaglia, M Mongillo, E Hirsch, A Ghigo, C Bauters, P De Groote, A Foinquinos, R Boon, LJ De Windt, S Batkai, F Pinet, T Thum, C Choquet, F Kober, M Bernard, RG Kelly, L Miquerol, N Lalevee, A Holmes, T Yu, S Tull, S Kuhlmann, D Pavlovic, D Betney, G Riley, JP Kucera, F Jousset, J De Groot, S Rohr, N Brown, L Fabritz, P Kirchhof
Journal: Cardiovascular Research (2016)

Background: Myocardial infarction (MI) causes cell death and triggers hypertrophic remodeling of surviving cardiomyocytes, resulting in heart failure.A therapeutic approach aiming at inducing cardiomyocyte proliferation while inhibiting the hypertrophic response would improve cardiac function and prevent MI-induced heart failure.By bioinformatics analyses, we identified the miR-106b 25 cluster to potentially target a network of negative cell cycle regulators, as well as series of prohypertrophic factors, indicating this microRNA cluster to possess a central role in recovering the heart muscle after myocardial injury.Hypothesis: Overexpression of the miR-106b 25 cluster recovers the heart muscle after MI by stimulating cardiomyocyte proliferation and inhibiting hypertrophy.Methods and Results: The miR-106b 25 cluster contains 3 co-expressed microRNAs: miR-106b, miR-93 and miR-25.Experiments in primary cardiomyocytes demonstrated that inhibition of miR-106b, miR-93 and miR-25 increases cell size, while overexpression of the miR-106b 25 cluster inhibited phenylephrine (PE)-induced hypertrophy.By performing fluorescent EdU labeling, we demonstrate that the miR-106b 25 cluster stimulates cardiomyocyte proliferation.Also, in vivo overexpression of miR-106b, miR-93, and miR-25 using adeno-associated virus 9 (AAV9) in neonatal mice induce an increased incorporation of EdU into cardiomyocytes, combined with increased levels of the proliferative markers Aurora-B and phosho-histone 3 (pH3), while cardiomyocyte size was not affected.In line, in adult mice, AAV9-miR106b 25 treatment increases heart mass without inducing hypertrophy, as indicated by both WGA staining and RT-qPCR experiments measuring transcript abundance of the hypertrophic genes Nppa, Nppb and Myh7, showing no difference between the experimental groups.To test the regenerative potential of myocyte proliferation secondary to AAV9-miR-106b 25 gene transfer, mice were randomized to receive a control AAV9-MCS (empty vector) or AAV9-miR-106b 25 and sham surgery or myocardial infarction (MI).Echocardiographic measurements demonstrate improvement of cardiac function after MI upon AAV9-miR106b 25 treatment versus AAV9-MCS, which is associated with a reduced infarction size and a clear decrease in fibrotic damage, as shown by Sirius-Red staining.Finally, to unravel the underlying mechanism by which the miR-106b 25 cluster stimulates cardiomyocyte proliferation, we performed luciferase-reporter assays, which identified negative cell cycle inhibitors Cdk1a, Cdk1c, and E2F5 as direct downstream targets.Conclusion: Our data demonstrate that AAV9-miR106b 25 treatment reduces scar formation and improves cardiac function after MI by stimulating cardiomyocyte proliferation and inhibiting hypertrophic remodeling.These findings might give rise to a new regenerative approach aiming at healing the cardiac muscle after myocardial injury.