Abstract 16716: Inhibition of Microrna-146a Enhances Angiogenesis and Functional Recovery After Myocardial Infarction and Hindlimb Ischemia
Background: Regeneration and functional recovery following ischemia critically depends on angiogenic processes in the affected tissue. MicroRNAs (miRs), a class of small non-coding RNAs that regulate gene expression by targeting mRNA for cleavage or translational repression, have been shown to influence angiogenesis; however, the key regulators and underlying mechanisms are incompletely defined.
Methods and Results: In ischemic tissues of C57BL/6J mice following myocardial infarction as well as hindlimb ischemia, expression levels of miR-146a were strongly upregulated (myocardial infarction: 3,5-fold after 48h; hindlimb: 14-fold after 72h). In vitro, transfection of endothelial cells with pre-miR-146a significantly attenuated cell proliferation and migration, abrogated endothelial capillary network formation on Matrigel and inhibited cell sprouting from endothelial spheroids. In contrast, an efficient knock-down by antagomiR-146a significantly augmented endothelial cell proliferation, migration, network formation, and sprouting. Among other confirmed targets, NADPH oxidase 4 (Nox4) was identified as direct target of miR-146a and validated by luciferase gene reporter assays. Following hind limb ischemia, systemic application of antagomiR-146a led to enhanced blood vessel growth and blood flow, as determined by histological analysis and laser Doppler imaging, (perfusion recovery: 61.3±18.1% vs. 38.4±11.1%; n=4; P<0.05). Moreover, systemic application of antagomiR-146a after permanent ligation of the left anterior descending coronary artery resulted in a significantly improved cardiac function, as assessed by echocardiography (fractional shortening: 22±4 vs. 11±2; n=6; P<0.01), reduced myocardial infarct size (LV infarct size: 41,6±4,1% vs. 62.7±3.5%; n=5; P<0.01), as assessed by picrosirius-red staining, and increased vascularity in the peri-infarct zone (16.7±1.2 vs. 9.4±1.2 a.u.; n=5; P<0.01).
Conclusions: Our data indicate that miR-146a acts as a critical regulator of angiogenesis during ischemic tissue regeneration. Moreover, miR-146a may represent an attractive target for future therapeutic interventions for the treatment of ischemic heart disease or peripheral arterial disease.
- © 2013 by American Heart Association, Inc.