Identification of upregulated microRNAs in the plasma of patients with acute myocardial infarction

Background: the discovery of new biomarkers in the setting of acute myocardial infarction (AMI) would be desirable for both diagnostic and prognostic purposes. Because of their tissue specificity and stability in the plasma, microRNAs (miRNA) hold promise as potential biomarkers. Recently, upregulation of specific circulating miRNA has been described in various diseases. Aim of our study was to evaluate the levels of circulating miRNA in AMI patients. Methods: plasma was collected from: 18 AMI patients at the time of admission (T0), after 24 hours (T1) and 7 days (T2); 18 sex- and age-matched patients with stable angina; 18 healthy donors. We performed Illumina MicroRNA Expression Profiling Array (Human v2 Panel) that can recognize 1146 human miRNA and analyzed the data with the dedicated software GenomeStudio Gene Expression. Differential expression (DS) was calculated using the Illumina Custom error model. The results obtained with the array were validated using the TaqMan MicroRNA qPCR. For selected miRNA, we calculated the area under the ROC curve (AUC) and the correlation with CK-MB peak. Results: using as cut-off a DS>13 (p<0.05), a total of 65 miRNA were upregulated at any time point in AMI patients compared with controls. Applying a more stringent statistical analysis (DS>20; p<0.01) and excluding those miRNA with an average level similar to the background, the number of miRNA upregulated at one or more consecutive time points was reduced to 10: two at T0, two at T1 and seven at T2. The qPCR analysis confirmed that two of these miRNA were upregulated at T0 (HS_52 and miR-423-5p), one at T1 (miR-345) and three at T2 (miR-1233, miR-362-3p and miR-483-3p). The ROC analysis showed a remarkably high diagnostic accuracy for the miRNA HS_52 at T0 (AUC=0.89). Furthermore, the level of HS_52 positively correlated with the CK-MB peak, a classic biomarker of AMI (r=0.46). Conclusions: we identified six circulating miRNA that are significantly elevated after AMI. Our finding paves the way for the search of the possible role of these miRNA in the response to acute myocardial ischemia/infarction and as potential diagnostic tool. For this latter purpose, our data suggest that miRNA HS_52 seems a strong candidate and may represent a novel biomarker in the setting of AMI.