Background-Recently, elevation of circulating muscle-specific microRNA (miRNA) levels has been reported in patients with acute myocardial infarction. However, it is still unclear from which part of the myocardium or under what conditions miRNAs are released into circulating blood. The purpose of this study was to identify the source of elevated levels of circulating miRNAs and their function in cardiovascular diseases. Methods and Results-Serum levels of miRNA (miR)-1 and miR-133a were increased significantly in patients not only with acute myocardial infarction but also with unstable angina pectoris and Takotsubo cardiomyopathy without elevation of serum creatine phosphokinase or cardiac troponin. MicroRNA microarray analysis of the heart from a mouse model of myocardial infarction indicated that the levels of miR-1, miR-133a, miR-208a, and miR-499 were significantly reduced in the infarcted myocardium. In situ hybridization of miR-133a also showed that miR-133a levels were very low in the infarcted and peri-infarcted myocardium. It has been shown that circulating miRNAs are localized inside exosomes, which are released after Ca 2ϩ stimulation. We stimulated H9c2 cardiomyoblasts with A23187 and measured miR-133a levels in the exosome fraction of the culture medium. A23187 induced a dose-dependent release of miR-133a, and significant elevation was observed only at concentrations where dead cells were detected. We also found that miR-133a-containing exosomes reduced the luciferase activity of 293FT cells transfected with an miR-133a sensor vector. Conclusions-These results suggest that elevated levels of circulating miR-133a in patients with cardiovascular diseases originate mainly from the injured myocardium. Circulating miR-133a can be used as a marker for cardiomyocyte death, and it may have functions in cardiovascular diseases. (Circ Cardiovasc Genet. 2011;4:446-454.)Key Words: circulating microRNA Ⅲ myocardial infarction Ⅲ cell death Ⅲ calcium ionophore M icroRNAs (miRNAs) are endogenous, single-stranded, Ϸ22-nucleotide noncoding RNAs. MicroRNAs are generally regarded as negative regulators of gene expression through inhibition of translation and/or promotion of mRNA degradation by base-pairing to complementary sequences within the 3Ј untranslated region (3ЈUTR) of protein-coding mRNA transcripts. 1 The first miRNA assigned to a specific function was lin-4, which targets lin-14 during temporal pattern formation in Caenorhabditis elegans. 2 Since then, a variety of miRNAs have been discovered. More than 500 miRNAs have been cloned and sequenced in humans, and the estimated number of miRNA genes may be as high as 1000 in the human genome. 3 Each miRNA regulates dozens to hundreds of distinct target genes; thus miRNAs are estimated to regulate the expression of more than one-third of human protein-coding genes. 4 Clinical Perspective on p 454The implications of miRNAs in the pathological process of the cardiovascular system have been recognized recently, and research on miRNAs in relation to cardiovascular dise...

No abstract

Background-The influences of antiplatelet therapy discontinuation on the risk of stent thrombosis and long-term clinical outcomes after drug-eluting stent implantation have not yet been addressed adequately. Methods and Results-In an observational study in Japan, 2-year outcomes were assessed in 10 778 patients undergoing sirolimus-eluting stent implantation. Data on status of antiplatelet therapy during follow-up were collected prospectively. Incidences of definite stent thrombosis were 0.34% at 30 days, 0.54% at 1 year, and 0.77% at 2 years. Thienopyridine use was maintained in 97%, 62%, and 50% of patients at 30 days, 1 year, and 2 years, respectively. Patients who discontinued both thienopyridine and aspirin had a significantly higher rate of stent thrombosis than those who continued both in the intervals of 31 to 180 days, 181 to 365 days, and 366 to 548 days after stent implantation (1.76% versus 0.1%, PϽ0.001; 0.72% versus 0.07%, Pϭ0.02; and 2.1% versus 0.14%, Pϭ0.004, respectively). When discontinuation of aspirin was taken into account, patients who discontinued thienopyridine only did not have an excess of stent thrombosis in any of the time intervals studied. Adjusted rates of death or myocardial infarction at 24 months were 4.1% for patients taking thienopyridine and 4.1% for patients not taking thienopyridine (Pϭ0.99) in the 6-month landmark analysis. Conclusions-Discontinuation of both thienopyridine and aspirin, but not discontinuation of thienopyridine therapy only, was associated with an increased risk of stent thrombosis. Landmark analysis did not suggest an apparent clinical benefit of thienopyridine use beyond 6 months after sirolimus-eluting stent implantation. (Circulation. 2009;119:987-995.)