Fig. 3

miR-27b is cardioprotective and pro-angiogenic in a mouse model of myocardial infarction (MI). MI was induced in C57Bl6 mice by ligating left coronary artery. Negative control RNAi (NC) or miR-27b mimics were formulated with Jet-PEI and injected into cardiac muscle at the time of surgery (10 μg/mouse). Transthoracic echocardiography was performed 14 and 28 days post-surgery and the animals were sacrificed on day 28. (a, b) Immunohistochemistry (a) and quantitative analysis (b) of the endothelial marker, CD31, in the hearts of mice treated with NC or miR-27b. The data is presented as boxplot with whiskers. P value was calculated by Kruskal-Wallis method. (c, d) Apical heart sections were assessed for fibrosis using Masson-Trichrome staining. (c) Representative images of the hearts treated with NC and miR-27b mimic (27b), respectively. Arrows point to the areas of fibrosis (blue). (d) Quantitative analysis of fibrotic areas was performed using Nikon Elements software; data is shown as dot plot with whiskers. P value was calculated by Kruskal-Wallis method. (e) Five-μm horizontal apical sections of the hearts treated as indicated were stained for collagen 1, for additional assessment of fibrosis. (f) Total RNA was extracted from cryopreserved tissue isolated from the infarcted areas and expression of Collagen I (Col I) measured by real-time RT-PCR with GAPDH served as an internal control. Data is presented as dot plot with whiskers. P value was determined using Mann–Whitney (Wilcoxon) test. (g, h) Left ventricular cardiac function, including ejection fraction (g) and fractional shortening (h) were measured using images obtained by two-dimensional M-mode echocardiography; statistical analysis was performed using Kruskal-Wallis test. Note a significant increase in the ejection fraction at day 14 in the hearts treated with miR-27b