MiR-223-3p and miR-122-5p as circulating biomarkers for plaque instability.

BACKGROUND: In this study, we discovered and validated candidate microRNA (miRNA) biomarkers for coronary artery disease (CAD). METHOD: Candidate tissue-derived miRNAs from atherosclerotic plaque material in patients with stable coronary artery disease (SCAD) (n=14) and unstable coronary artery disease (UCAD) (n=25) were discovered by qPCR-based arrays. We validated differentially expressed miRNAs, along with seven promising CAD-associated miRNAs from the literature, in the serum of two large cohorts (n=395 and n=1000) of patients with SCAD and UCAD and subclinical atherosclerosis (SubA) and controls, respectively. RESULT: From plaque materials (discovery phase), miR-125b-5p and miR-193b-3p were most upregulated in SCAD, whereas miR-223-3p and miR-142-3p were most upregulated in patients with UCAD. Subsequent validation in serum from patients with UCAD, SCAD, SubA and controls demonstrated significant upregulation of miR-223-3p, miR-133a-3p, miR-146-3p and miR-155-5p. The ischaemia-related miR-499-5p was also highly upregulated in patients with UCAD compared with the other groups (SCAD OR 20.63 (95% CI 11.16 to 38.15), SubA OR 96.10 (95% CI 40.13 to 230.14) and controls OR 15.73 (95% CI 7.80 to 31.72)). However, no significant difference in miR-499-5p expression was observed across SCAD, SubA and controls. MiR-122-5p was the only miRNA to be significantly upregulated in the serum of both patients with UCAD and SCAD. CONCLUSION: In conclusion, miR-122-5p and miR-223-3p might be markers of plaque instability.

High miR-124-3p expression identifies smoking individuals susceptible to atherosclerosis.

BACKGROUND AND AIMS: The risk of developing cardiovascular disease (CVD) is twice as high among smoking individuals compared to non-smokers. Monocytes are involved in smoking-related atherosclerotic plaque formation. In this study, we investigated whether smokers with an increased risk of developing CVD can be identified on the basis of monocyte-derived miRNA expression levels. METHODS: We performed a miRNA microarray experiment on isolated monocytes from smoking, former smoking and non-smoking individuals in a cohort of patients with premature CVD and healthy controls (Cohort I, n = 76). RESULTS: We found miR-124-3p to be heterogeneously expressed among all smoking individuals, whereas expression was low in non-smokers. Subsequently, RT-qPCR measurements on whole blood showed that among smoking individuals an increase in miR-124-3p is associated with an increased risk for advanced atherosclerotic disease (cohort II, n = 24) (OR 11.72 95% CI 1.09-126.53) and subclinical atherosclerosis (coronary artery calcium score ≥ 80th percentile, cohort III n = 138) (OR 2.71, 95% CI 1.05-7.01). This was not observed among former smokers or non-smoking individuals. Flow cytometric analysis demonstrated that high miR-124-3p expression was associated with upregulation of the monocyte surface markers CD45RA, CD29 and CD206, indicating an altered monocyte phenotype. Finally, overexpression of miR-124-3p resulted in an upregulation of CD206 surface expression on monocytes. CONCLUSIONS: High miR-124-3p expression is associated with an increased risk of subclinical atherosclerosis in smoking individuals and with an altered monocyte phenotype. This may suggest that miR-124-3p identifies which smoking individuals are susceptible to the atherogenic effects of smoking.

Practical data handling pipeline improves performance of qPCR-based circulating miRNA measurements.

Since numerous miRNAs have been shown to be present in circulation, these so-called circulating miRNAs have emerged as potential biomarkers for disease. However, results of qPCR studies on circulating miRNA biomarkers vary greatly and many experiments cannot be reproduced. Missing data in qPCR experiments often occur due to off-target amplification, nonanalyzable qPCR curves and discordance between replicates. The low concentration of most miRNAs leads to most, but not all missing data. Therefore, failure to distinguish between missing data due to a low concentration and missing data due to randomly occurring technical errors partly explains the variation within and between otherwise similar studies. Based on qPCR kinetics, an analysis pipeline was developed to distinguish missing data due to technical errors from missing data due to a low concentration of the miRNA-equivalent cDNA in the PCR reaction. Furthermore, this pipeline incorporates a method to statistically decide whether concentrations from replicates are sufficiently concordant, which improves stability of results and avoids unnecessary data loss. By going through the pipeline's steps, the result of each measurement is categorized as "valid, invalid, or undetectable." Together with a set of imputation rules, the pipeline leads to more robust and reproducible data as was confirmed experimentally. Using two validation approaches, in two cohorts totaling 2214 heart failure patients, we showed that this pipeline increases both the accuracy and precision of qPCR measurements. In conclusion, this statistical data handling pipeline improves the performance of qPCR studies on low-expressed targets such as circulating miRNAs.

Normalization panels for the reliable quantification of circulating microRNAs by RT-qPCR.

Circulating microRNAs (miRNAs) have been reported as biomarkers for disease diagnosis. RT-qPCR is most commonly used to detect miRNAs; however, no consensus on the most appropriate method for data normalization exists. Via a standardized selection method, we aimed to determine separate miRNA normalization panels for RT-qPCR measurements on whole blood, platelets, and serum. Candidate miRNAs were selected from studies describing circulating miRNA microarray data in the Gene Expression Omnibus or ArrayExpress. miRNA expression data of healthy controls were retrieved from each study. For each sample type, we selected those miRNAs that were least variable and sufficiently highly expressed in multiple microarray experiments, performed on at least 2 different platforms. Stability of the candidate miRNAs was assessed using NormFinder and geNorm algorithms in a RT-qPCR cohort of 10 patients with coronary artery disease and 10 healthy controls. We selected miRNA normalization panels for RT-qPCR measurements on whole blood, platelets, and serum. As a validation, we assessed the precision of all 3 panels in 3 independent RT-qPCR cohorts and compared this with normalization for miR-16 or RNU6B. The proposed normalization panels for whole blood, platelets, and serum show better precision than normalization for miR-16 or RNU6B.

Individual with subclinical atherosclerosis have impaired proliferation of blood outgrowth endothelial cells, which can be restored by statin therapy.

BACKGROUND: To study the regenerative capacity of the endothelium in patients with coronary artery disease (CAD), we cultured blood outgrowth endothelial cells (BOECs) of patients with premature CAD and their first degree relatives (FDR). Additionally we evaluated the influence of statin treatment on circulating BOEC precursors in subjects with subclinical atherosclerosis. METHODS AND RESULTS: Patients with premature CAD (men <51 yr, women <56 yr) and their FDRs were included. Based on coronary calcification (CAC) scores FDRs were divided in a group of healthy subjects (CAC = 0) and subjects with subclinical atherosclerosis (CAC>0). We did not observe differences in the number of BOEC colonies and proliferation between premature CAD patients and FDRs. FDRs with subclinical atherosclerosis had lower colony numbers compared with healthy FDRs, however this was not statistically significant, and BOEC proliferation was significantly impaired (OR = 0.45, 95% CI 0.21-0.96). Unexpectedly, the number of BOEC colonies and BOEC proliferation were similar for premature CAD patients and healthy FDRs. Since a considerable number of premature CAD patients used statins, we studied the number of BOEC precursors as well as their proliferative capacity in ten individuals with subclinical atherosclerosis, before and after statin therapy. Interestingly, FDRs with subclinical atherosclerosis showed a significant increase in the number of BOEC colonies after statin therapy. CONCLUSION: BOEC proliferation of subjects with subclinical atherosclerosis is impaired compared with healthy controls. In these subjects, statin therapy significantly increased the number of circulating BOEC precursors as well as their proliferative capacity, revealing a beneficial effect of statins on endothelial regeneration.

Platelets in patients with premature coronary artery disease exhibit upregulation of miRNA340* and miRNA624*.

BACKGROUND: Coronary artery disease (CAD) is the leading cause of human morbidity and mortality worldwide, underscoring the need to improve diagnostic strategies. Platelets play a major role, not only in the process of acute thrombosis during plaque rupture, but also in the formation of atherosclerosis itself. MicroRNAs are endogenous small non-coding RNAs that control gene expression and are expressed in a tissue and disease-specific manner. Therefore they have been proposed to be useful biomarkers. It remains unknown whether differences in miRNA expression levels in platelets can be found between patients with premature CAD and healthy controls. METHODOLOGY/PRINCIPAL FINDINGS: In this case-control study we measured relative expression levels of platelet miRNAs using microarrays from 12 patients with premature CAD and 12 age- and sex-matched healthy controls. Six platelet microRNAs were significantly upregulated (miR340*, miR451, miR454*, miR545:9.1. miR615-5p and miR624*) and one miRNA (miR1280) was significantly downregulated in patients with CAD as compared to healthy controls. To validate these results, we measured the expression levels of these candidate miRNAs by qRT-PCR in platelets of individuals from two independent cohorts; validation cohort I consisted of 40 patients with premature CAD and 40 healthy controls and validation cohort II consisted of 27 patients with artery disease and 40 healthy relatives. MiR340* and miR624* were confirmed to be upregulated in patients with CAD as compared to healthy controls in both validation cohorts. CONCLUSION/SIGNIFICANCE: Two miRNAs in platelets are significantly upregulated in patients with CAD as compared to healthy controls. Whether the two identified miRNAs can be used as biomarkers and whether they are cause or consequence of the disease remains to be elucidated in a larger prospective study.

Incidental venous thromboembolism in cancer patients: prevalence and consequence.

INTRODUCTION: Careful re-evaluation of CT-scans for cancer staging frequently reveals unsuspected venous thromboembolism (VTE) on CT-scans. However, it is unknown how often these findings lead to anticoagulant treatment in daily clinical practice. METHODS: Reports from thoracic and/or abdominal CT-scans performed in a consecutive series of patients to stage cancer were retrospectively evaluated to determine the prevalence of incidental venous thromboembolism (iVTE). Presence of pre-existing signs of VTE, anticoagulant treatment and 3-month follow-up were analysed in patients with iVTE. RESULTS: A total of 1466 staging scans (838 patients) from the year 2006 were included in the analysis. The prevalence of VTE in patients was 2.5% (21/838 patients, 95% confidence interval 1.6-3.8%); the prevalence of VTE on scans was 1.4% (21/1466 scans, 95% CI 0.9-2.2%). Incidental PE or deep vein thrombosis (DVT) was observed in 11 (1.3%, 0.7-2.3%) and abdominal vein thrombosis in 9 patients (1.1%, 0.6-2.0%; in the portal (5), mesenteric (3) and renal vein (1), respectively). Nine out of eleven patients with PE/DVT were treated with anticoagulants, while none of the patients with thrombosis in other locations received anticoagulants. One of these patients developed symptomatic PE one month later; otherwise, follow up was uneventful in the untreated patients. CONCLUSION: The prevalence of iVTE in patients with cancer in clinical practice is relatively low and most patients with PE or DVT are treated with anticoagulants. For patients with thrombi in other locations, further research is necessary to understand the natural history of these thrombi in order to develop adequate guidelines.