Abstract 14023: Inhibition of the Age-induced microRNA-34 Improves Recovery After AMI in Mice
Aging is the major risk factor for developing complications like acute myocardial infarction (AMI) and chronic heart failure. The mechanisms involved in cardiac aging are poorly understood, but microRNAs (miRNAs) are emerging as key biological regulators. Therefore, we investigated the changes in mRNA and miRNA expression of the heart in aged mice (18 months old) compared to young mice (6 weeks old) by microarray expression profiling. Amongst the most significantly upregulated miRNAs in hearts of aged mice was the entire miR-34 family (miR-34a, b and c). MiR-34 has previously been implicated in apoptosis, partly through the suppression of SIRT1, which we show to be regulated by age in the heart (45.0±7.4% inhibition, p<0.05). Inhibition of miR-34a in 18 month old mice using specific antagomirs against miR-34a (Ant-34a) reduced apoptosis in the heart (70.6±6.0% inhibition, p<0.05), compared to scrambled control antagomir (Ant-Control) treated mice. Furthermore, we found that miR-34a is induced 2.4-fold at day 7 after AMI in mice and silencing of miR-34a after AMI induction improves recovery. This is evidenced by an improvement in ejection fraction (EF) and wall motion score index (WMSI) 14 days after AMI in mice treated with Ant-34a as compared to Ant-Control treated mice (EF: Ant-Control: 19.9±2.3%, Ant-34a: 36.8±3.7%, p<0.05; WMSI: Ant-Control: 2.14±0.16, Ant-34a: 1.53±0.12, p<0.05), as well as apoptosis and fibrosis (74.0±15.4% and 68±10.1% inhibition, p<0.05, resp.). Mechanistically, we identified several novel additional potential targets of miR-34, of which PNUTS (PPP1R10) is most strongly downregulated in aged hearts (89.4±4.2% inhibition, p<0.05). PNUTS is known to be involved in apoptosis and to interact with the telomere regulator TRF2. Regulation of PNUTS by miR-34 is confirmed in vitro using the miR-34 binding site in the 3′UTR of PNUTS in a luciferase assay and in vivo in the heart after Ant-34a treatment. Furthermore, we show that miR-34a transfection in cultured rat cardiomyocytes augments H2O2-induced apoptosis, which is rescued by lentiviral overexpression of PNUTS. Together, these results indicate that in vivo silencing of miR-34 reverses the adverse effects of aging on the heart and improves cardiac function after AMI.
- © 2010 by American Heart Association, Inc.