br Discussion The results of our study have revealed

Discussion The results of our study have revealed for the first time that combination of NT-proBNP and CD31+/annexin V+ EMPs to CD14+CD309+ cell ratio is a useful biomarker for chronic HF, which contributes in the differentiation of HFpEF from HFrEF. We have demonstrated that HF patients have exhibited elevated levels of EPCs with angiopoetic capacities, apoptotic-derived EMCs, as well as decreased level of CD62E+ EMPs secreted by activated endothelial cells. Recently higher level of CD62+ EMP secreted from activated endothelial buy EZ Cap Reagent GG (3\' OMe) in the healthy subjects versus HF patients was related to rather endothelial dysfunction than endothelial cell injury) (Dignat-George and Boulanger, 2011; Burger and Touyz, 2012). In our study we did not find any significance changes between HFrEF and HFpEF patients, probably due to similar molecular mechanisms that might lead to endothelial cell activation. We have suggested that lack of sufficient difference between co-morbidities\' presentation among HFrEF and HFpEF groups might express similar finding. Interestingly, because of the number of existing CV risk factors which are variable between HF patients, simple EPC counts do not adequately describe vascular disease risk in all clinical conditions and, as such, the CV risk remains (Sen et al., 2011). However, the imbalance in pattern of circulating EMPs and EPCs might affect endothelium ability to repair and previously we have described similar changes as “impaired” phenotype (Berezin, 2015b). The concept of “impaired” phenotype as imbalance between factors originating from endothelium with innate angiogenic and/or injury capacities directly contributed in the endothelial dysfunction and requires further investigation because the molecular mechanism of their release into circulation still remains elusive. Because biomarkers\' levels might suggest different amounts of activation of several pathophysiological pathways between HFpEF and HFrEF development (Sanders-van Wijk et al., 2015; Kaila et al., 2012), we have hypothesized that numerous apoptotic EMPs to EPCs might be distinguished in HFpEF and HFpEF individuals. It is important to note that recent clinical studies have shown increased serum level of NT-proBNP as powerful predictive factor in both HFpEF and HFrEF, although patients with HFpEF exhibits lower NT-proBNP levels (Kang et al., 2015). Several biomarkers, i.e. soluble suppression of tumorigenicity 2 protein, galectin-3, cardiac specific troponins, provides robust prognostic information in HFrEF, but not for HFpEF, while they could improve the prognostication pattern via adding to NT-proBNP in predictive model (Friões et al., 2015). In the LUdwigshafen Risk and Cardiovascular Health (LURIC) study high-sensitive C-reactive protein was found to be an independent and strong predictor of mortality in HFpEF (Koller et al., 2014), but this biomarker even after adding to predictive model based on NT-proBNP was not able to predict HFpEF development. Overall, discriminative values of several cardiac biomarkers including NT-proBNP to stratify patients with HFpEF and HFrEF are not fully adequate. Apoptotic EMPs are considered a marker of endothelial cell injury and a factor that contributed in transferring biological information, active molecules, hormones, proteins, lipid components, as well as regulating cell homeostasis and cell response (Sansone et al., 2015; Bank et al., 2015). Interestingly, apoptotic EMPs may directly injure endothelium (Montoro-García et al., 2015). In contrast, EPCs labeled as CD14+CD309+ and CD14+СD309+ Tie-2+ have citoprotective action; they are capable of repairing endothelium and restoring of endothelial function (Sandri et al., 2015; Berezin and Kremzer, 2015a,b). In this context, decreased CD31+/annexin V+ EMPs and increased CD14+CD309+ cells might elucidate reparative ability of endothelium. Recent clinical studies have shown that numerous of EPCs defined as CD34+ CD309+ have failed to associate with CV risk factors, medications, HF etiology, age or gender of the patients, while low EPCs\' number was associated with an increased likelihood of abnormal left ventricular mass and worse cardiac remodeling (Michelucci et al., 2015; António et al., 2014). Numerous of CD31+/annexin V+ EMPs strongly correlate with endothelial function and CV outcomes in stable CAD patients (Sinning et al., 2011; Werner et al., 2006). Moreover, Huang et al. (2010) reported that increased circulating CD31+/annexin V+ EMPs and decreased circulating EPCs predict target organ damage in hypertensive patients. In our study HFpEF patients have exhibited lower CD31+/annexin V+ EMPs to CD14+CD309+ cell ratio and CD31+/annexin V+ EMPs to CD14+CD309+Tie-2+ cell ratio in comparison with HFrEF patients. The result of Cox-regression analysis adjusted etiology (previous myocardial infarction), cardiovascular risk factors (obesity, type 2 diabetes mellitus) has revealed that NT-proBNP and CD31+/annexin V+ EMPs to CD14+CD309+ cell ratio are independent predictors of HFpEF. Additionally, we found that the discriminative value of NT-proBNP as a HF diagnostic biomarker might improve by use in combination with CD31+/annexin V+ EMPs to CD14+CD309+ cell ratio, whereas increased number of CD31+/annexin V+ EMPs alone and decreased number of CD14+CD309+ cells alone were not able to improve the discriminative value of standard models based on combination of clinical features (previous myocardial infarction, obesity, type 2 diabetes mellitus) or NT-proBNP.