Platelets Purification Is a Crucial Step for Transcriptomic Analysis.

Platelets are small anucleate cells derived from the fragmentation of megakaryocytes and are involved in different biological processes especially hemostasis, thrombosis, and immune response. Despite their lack of nucleus, platelets contain a reservoir of megakaryocyte-derived RNAs and all the machinery useful for mRNA translation. Interestingly, platelet transcriptome was analyzed in health and diseases and led to the identification of disease-specific molecular signatures. Platelet contamination by leukocytes and erythrocytes during platelet purification is a major problem in transcriptomic analysis and the presence of few contaminants in platelet preparation could strongly alter transcriptome results. Since contaminant impacts on platelet transcriptome remains theoretical, we aimed to determine whether low leukocyte and erythrocyte contamination could cause great or only minor changes in platelet transcriptome. Using microarray technique, we compared the transcriptome of platelets from the same donor, purified by common centrifugation method or using magnetic microbeads to eliminate contaminating cells. We found that platelet transcriptome was greatly altered by contaminants, as the relative amount of 8274 transcripts was different between compared samples. We observed an increase of transcripts related to leukocytes and erythrocytes in platelet purified without microbeads, while platelet specific transcripts were falsely reduced. In conclusion, serious precautions should be taken during platelet purification process for transcriptomic analysis, in order to avoid platelets contamination and result alteration.

Platelets: a potential role in chronic respiratory diseases?

Platelets are small anucleate cells known for their role in haemostasis and thrombosis. In recent years, an increasing number of observations have suggested that platelets are also immune cells and key modulators of immunity. They express different receptors and molecules that allow them to respond to pathogens, and to interact with other immune cells. Platelets were linked to the pathogenesis of some inflammatory disorders including respiratory diseases such as asthma and idiopathic pulmonary fibrosis. Here, we discuss the involvement of platelets in different immune responses, and we focus on their potential role in various chronic lung diseases.

Epicardial adipose tissue extent: relationship with age, body fat distribution, and coronaropathy.

Epicardial fat is a relatively neglected component of the heart and could be an important risk factor of cardiac disease. The objective of our study was to assess the relationship between epicardial adipose tissue (EAT) extent, fat distribution, and coronaropathy in a group of adult victims of accidental or suspicious sudden death. In 56 cadavers, we performed 34 measurements of EAT from five computerized photographs of the heart (anterior and posterior faces, and three ventricle transversal slices) and analyzed their relationship with anthropometric markers of adiposity (BMI, waist and leg circumference, thickness of abdominal and thigh subcutaneous adipose tissue (SAT)), with the presence and staging of coronary artery disease (CAD), and with markers of myocardial hypertrophy. Simple linear regressions showed that EAT measurements are highly intercorrelated (r from 0.4 to 0.6, P < 0.001), and correlate with age, waist circumference, and heart weight, and to a lesser extent, with BMI, abdominal SAT thickness, and leg SAT thickness. Multiple regression showed that age, waist circumference, and heart weight significantly and independently correlate with EAT (P < 0.0001). No other anthropometric measurement was found independently correlated with EAT. The EAT/myocardium ratios correlated positively with age and waist circumference. Anterior and posterior areas of EAT were found significantly increased in patients with CAD and correlated positively with CAD staging (P = 0.0034, r = 0.38). Anterior EAT surface was found positively associated with CAD (P = 0.01), independently of age and other adiposity measurements. Prospective studies are needed to assess the risk of occurrence/progression of CAD that relate to EAT excess.

Association between TAFI antigen and Ala147Thr polymorphism of the TAFI gene and the angina pectoris incidence. The PRIME Study (Prospective Epidemiological Study of MI).

Thrombin activatable fibrinolysis inhibitor (TAFI), a recently described inhibitor of fibrinolysis, has been hypothesized as playing a role in atherothrombosis. However, the evidence from retrospective studies, which have evaluated the role of TAFI in vascular risk, is conflicting. In a prospective cohort (the PRIME Study) of nearly 10 000 apparently healthy men recruited in France (Lille, Strasbourg, Toulouse) and Northern Ireland (Belfast), we measured baseline plasma concentration of TAFI antigen among 143 participants (81 from France and 62 from Ireland) who subsequently developed angina pectoris and among 286 age-matched participants who remained free of disease during the 5 years of follow-up. Genotyping of the Ala147Thr polymorphism located in the TAFI gene was performed using an allele specific PCR. In France, mean levels of TAFI were significantly higher at baseline among men who subsequently developed angina pectoris compared with their control subjects (119 versus 107 %; p = 0.02). The risk of future angina pectoris increased with increasing tertiles of TAFI (p = 0.02), such that men in the highest tertile at study entry had a 5-fold higher relative risk than those in the lowest tertile (95% confidence interval, 1.38 to 18.58) after controlling for the conventional cardiovascular risk factors. No such difference was observed in Northern Ireland. In France, Thr/Thr carriers of the Ala147Thr polymorphism were significantly more frequent in cases than in controls (p = 0.01) leading to a relative risk of angina pectoris of 2.7 (95%CI 1.2-5.8). Increase in plasma TAFI antigen levels is a risk factor for angina pectoris in France. Genotyping for the Ala147Thr polymorphism seems to be a reliable tool to assess the risk mediated by TAFI.