Stent thrombosis (ST) is a serious complication following coronary stenting. Intravascular optical coherence tomography (OCT) may provide insights into mechanistic processes leading to ST. We ...performed a prospective, multicenter study to evaluate OCT findings in patients with ST.
Consecutive patients presenting with ST were prospectively enrolled in a registry by using a centralized telephone registration system. After angiographic confirmation of ST, OCT imaging of the culprit vessel was performed with frequency domain OCT. Clinical data were collected according to a standardized protocol. OCT acquisitions were analyzed at a core laboratory. Dominant and contributing findings were adjudicated by an imaging adjudication committee.
Two hundred thirty-one patients presenting with ST underwent OCT imaging; 14 (6.1%) had image quality precluding further analysis. Of the remaining patients, 62 (28.6%) and 155 (71.4%) presented with early and late/very late ST, respectively. The underlying stent type was a new-generation drug-eluting stent in 50.3%. Mean reference vessel diameter was 2.9±0.6 mm and mean reference vessel area was 6.8±2.6 mm
. Stent underexpansion (stent expansion index <0.8) was observed in 44.4% of patients. The predicted average probability (95% confidence interval) that any frame had uncovered (or thrombus-covered) struts was 99.3% (96.1-99.9), 96.6% (92.4-98.5), 34.3% (15.0-60.7), and 9.6% (6.2-14.5) and malapposed struts was 21.8% (8.4-45.6), 8.5% (4.6-15.3), 6.7% (2.5-16.3), and 2.0% (1.2-3.3) for acute, subacute, late, and very late ST, respectively. The most common dominant finding adjudicated for acute ST was uncovered struts (66.7% of cases); for subacute ST, the most common dominant finding was uncovered struts (61.7%) and underexpansion (25.5%); for late ST, the most common dominant finding was uncovered struts (33.3%) and severe restenosis (19.1%); and for very late ST, the most common dominant finding was neoatherosclerosis (31.3%) and uncovered struts (20.2%). In patients presenting very late ST, uncovered stent struts were a common dominant finding in drug-eluting stents, and neoatherosclerosis was a common dominant finding in bare metal stents.
In patients with ST, uncovered and malapposed struts were frequently observed with the incidence of both decreasing with longer time intervals between stent implantation and presentation. The most frequent dominant observation varied according to time intervals from index stenting: uncovered struts and underexpansion in acute/subacute ST and neoatherosclerosis and uncovered struts in late/very late ST.
Cardiovascular (CV) death remains the largest cause of mortality in dialysis patients, unexplained by traditional risk factors. Endothelial microvesicles (EMVs) are elevated in patients with ...traditional CV risk factors and acute coronary syndromes while platelet MVs (PMVs) are associated with atherosclerotic disease states. This study compared relative concentrations of circulating MVs from endothelial cells and platelets in two groups of dialysis patients and matched controls and investigated their relative thromboembolic risk. MVs were isolated from the blood of 20 haemodialysis (HD), 17 peritoneal dialysis (PD) patients and 20 matched controls. Relative concentrations of EMVs (CD144(+ ve)) and PMVs (CD42b(+ ve)) were measured by Western blotting and total MV concentrations were measured using nanoparticle-tracking analysis. The ability to support thrombin generation was measured by reconstituting the MVs in normal plasma, using the Continuous Automated Thrombogram assay triggered with 1µM tissue factor. The total concentration of MVs as well as the measured sub-types was higher in both patient groups compared to controls (p<0.05). MVs from HD and PD patients were able to generate more thrombin than the controls, with higher peak thrombin, and endogenous thrombin potential levels (p<0.02). However there were no differences in either the relative quantity or activity of MVs between the two patient groups (p>0.3). Dialysis patients have higher levels of circulating procoagulant MVs than healthy controls. This may represent a novel and potentially modifiable mediator or predictor of occlusive cardiovascular events in these patients.
Extracellular vesicles (EVs) released from activated platelets contain microRNAs, the most abundant of which is hsa-miR-223-3p. Endogenous hsa-miR-223-3p suppresses the expression of tissue factor ...(TF), the initiator of the extrinsic coagulation pathway, in endothelial cells. Monocytes can be induced to express TF to enhance coagulation, but the role of hsa-miR-223-3p in regulating monocyte TF remains unknown. This study examined whether hsa-miR-223-3p from platelet-derived EVs (pdEVs) affects TF expression in monocytes. THP-1 cells, differentiated into a monocyte-like phenotype with 1α,25-dihydroxyvitaminD3, were transfected with hsa-miR-223-3p mimic or control microRNA. Alternatively, THP-1 cells were incubated with pdEVs from PAR1-agonist peptide activated-platelets, as platelet releasate, or pdEVs isolated by ultracentrifugation. Transfection with hsa-miR-223-3p mimic resulted in significant reductions in TF protein, determined by western blotting and flow cytometry and reduced procoagulant activity, measured by a TF-specific factor Xa generation assay, compared to cells transfected with control microRNA. This reduction was reversed by co-transfection with hsa-miR-223-3p inhibitor, AntagomiR-223. Incubation of THP-1 cells with pdEVs also decreased TF expression; however, this was not reversed by AntagomiR-223. Taken together, monocyte TF expression is downregulated by hsa-miR-223-3p, but when transferred via pdEVs the effect was not reversed with Antagomir-223, suggesting other pdEV components may contribute to TF regulation.
Abbreviations: Tissue factor (TF), Factor VII (FVII), activated Factor VII (FVIIa), Factor X (FX), activated Factor X (FXa), extracellular vesicles (EVs), microvesicles (MVs), platelet-derived extracellular vesicles (pdEVs), protease-activated receptor 1 agonist peptide (PAR1-AP), lipopolysaccharide (LPS), P-selectin glycoprotein ligand-1 (PSGL-1), Tris-Buffered Saline Tween (TBST), room temperature (RT)
Unfractionated heparin (UFH) is an effective antithrombotic during surgery but has known adverse effects, in particular on platelets. A marked increase in platelet responsiveness has previously been ...observed in patients within minutes of receiving UFH, despite adequate inhibition by aspirin prior to heparin. We studied this phenomenon in patients undergoing cardiac artery bypass grafting (n = 17) to determine whether the effects of heparin were systemic or platelet-specific. All patients' platelets were fully inhibited by aspirin prior to surgery, but within 3 min of receiving heparin spontaneous aggregation and responses to arachidonic acid (AA) and ADP increased significantly (p ≥ 0.0002), and activated platelets were found in the circulation. While there was no rise in thromboxane in the plasma following heparin, levels of the major platelet 12-lipoxygenase product, 12-HETE, rose significantly. Mixing experiments demonstrated that the changes caused by heparin resided primarily in the platelets, while addition of AA pathway inhibitors, and analysis of oxylipins provided evidence that, following heparin, aggregating platelets regained their ability to synthesise thromboxane. These findings highlight potentially unrecognised pro-thrombotic and pro-inflammatory changes during CABG surgery, and provide further evidence of adverse effects associated with UFH.
Apoptosis in megakaryocytes results in the formation of platelets. The role of apoptotic pathways in platelet turnover and in the apoptotic-like changes seen after platelet activation is poorly ...understood. ABT-263 (Navitoclax), a specific inhibitor of antiapoptotic BCL2 proteins, which is currently being evaluated in clinical trials for the treatment of leukemia and other malignancies, induces a dose-limiting thrombocytopenia. In this study, the relationship between BCL2/BCL-XL inhibition, apoptosis, and platelet activation was investigated. Exposure to ABT-263 induced apoptosis but repressed platelet activation by physiologic agonists. Notably, ABT-263 induced an immediate calcium response in platelets and the depletion of intracellular calcium stores, indicating that on BCL2/BCL-XL inhibition platelet activation is abrogated because of a diminished calcium signaling. By comparing the effects of ABT-263 and its analog ABT-737 on platelets and leukemia cells from the same donor, we show, for the first time, that these BCL2/BCL-XL inhibitors do not offer any selective toxicity but induce apoptosis at similar concentrations in leukemia cells and platelets. However, reticulated platelets are less sensitive to apoptosis, supporting the hypothesis that treatment with ABT-263 induces a selective loss of older platelets and providing an explanation for the transient thrombocytopenia observed on ABT-263 treatment.
The role of mechanosensitive (MS) Ca2+-permeable ion channels in platelets is unclear, despite the importance of shear stress in platelet function and life-threatening thrombus formation. We ...therefore sought to investigate the expression and functional relevance of MS channels in human platelets. The effect of shear stress on Ca2+ entry in human platelets and Meg-01 megakaryocytic cells loaded with Fluo-3 was examined by confocal microscopy. Cells were attached to glass coverslips within flow chambers that allowed applications of physiological and pathological shear stress. Arterial shear (1002.6 s−1) induced a sustained increase in Ca2+i in Meg-01 cells and enhanced the frequency of repetitive Ca2+ transients by 80% in platelets. These Ca2+ increases were abrogated by the MS channel inhibitor Grammostola spatulata mechanotoxin 4 (GsMTx-4) or by chelation of extracellular Ca2+. Thrombus formation was studied on collagen-coated surfaces using DiOC6-stained platelets. In addition, Ca2+i and functional responses of washed platelet suspensions were studied with Fura-2 and light transmission aggregometry, respectively. Thrombus size was reduced 50% by GsMTx-4, independently of P2X1 receptors. In contrast, GsMTx-4 had no effect on collagen-induced aggregation or on Ca2+ influx via TRPC6 or Orai1 channels and caused only a minor inhibition of P2X1-dependent Ca2+ entry. The Piezo1 agonist, Yoda1, potentiated shear-dependent platelet Ca2+ transients by 170%. Piezo1 mRNA transcripts and protein were detected with quantitative RT-PCR and Western blotting, respectively, in both platelets and Meg-01 cells. We conclude that platelets and Meg-01 cells express the MS cation channel Piezo1, which may contribute to Ca2+ entry and thrombus formation under arterial shear.
On activation platelets release microRNAs and extracellular vesicles (EV) into circulation. The release of EV from platelets has been shown to be dependent on the agonist; in this study, we ...investigated whether the microRNA profile or EV released from platelets was also agonist specific.
Washed platelets from healthy subjects were maximally stimulated with agonists specific for the receptors for collagen (Glycoprotein VI (GPVI)), thrombin (PAR1/PAR4), or ADP (P2Y1/P2Y12) with/without inhibiting secondary mediators, using aspirin to block cyclooxygenase-1 and apyrase to remove ADP. The released microRNAs were profiled using TaqMan microRNA microarray cards. Platelet-derived EV (pdEV) were characterized by size (Nanoparticle Tracking Analysis, NTA), for procoagulant activity (Annexin-V binding and support of thrombin generation), and for the EV markers CD63 and HSP70.
Platelet activation triggered the release of 57-79 different microRNAs, dependent upon agonist, with a core of 46 microRNAs observed with all agonists. There was a high level of correlation between agonists (r
2
> 0.98; p < 0.0001 for all), and with the microRNA content of the parent platelets (r
2
> 0.98; p < 0.0001). The 46 microRNAs seen in all samples are predicted to have significant effects on the translation of proteins involved in endocytosis, cell cycle control, and differentiation. MiR-223-3p was the most abundant in all samples and has previously been implicated in myeloid lineage development and demonstrated to have anti-inflammatory effects. Stimulation through GPVI produced a pdEV population with significantly more procoagulant activity than the other agonists. Apyrase significantly reduced microRNA and pdEV release, while aspirin had little effect.
These data suggest that all tested agonists trigger the release of a similar microRNA profile while the procoagulant activity of the pdEV was agonist dependent. ADP was shown to play an important role in the release of both microRNAs and pdEV.
OBJECTIVE—Biological age may be distinct from chronological age and contribute to the pathogenesis of age-related diseases. Mean telomeres lengths provide an assessment of biological age with shorter ...telomeres, indicating increased biological age. We investigated whether subjects with premature myocardial infarction (MI) had shorter leukocyte telomeres.
METHODS AND RESULTS—Mean terminal restriction fragment (TRF) length, a measure of average telomere size, was compared in leukocyte DNA of 203 cases with a premature MI (<50 years) and 180 controls. Age- and sex-adjusted mean TRF length of cases was significantly shorter than that of controls (difference 299.7±69.3 base pairs, P <0.0001) and on average equivalent to controls 11.3 years older. The difference in mean TRF length between cases and controls was not accounted for by other coronary risk factors. Compared with subjects in the highest quartile for telomere length, the risk of myocardial infarction was increased between 2.8- and 3.2-fold (P <0.0001) in subjects with shorter than average telomeres.
CONCLUSIONS—The findings support the concept that biological age may play a role in the etiology of coronary heart disease and have potentially important implications for our understanding of its genetic etiology, pathogenesis, and variable age of onset.
Smoking is a major risk factor in many diseases. Genome wide association studies have linked genes for nicotine dependence and smoking behavior to increased risk of cardiovascular, pulmonary, and ...malignant diseases. We conducted an epigenome wide association study in peripheral-blood DNA in 464 individuals (22 current smokers and 263 ex-smokers), using the Human Methylation 450 K array. Upon replication in an independent sample of 356 twins (41 current and 104 ex-smokers), we identified 30 probes in 15 distinct loci, all of which reached genome-wide significance in the combined analysis P < 5 × 10
−8
. All but one probe (cg17024919) remained significant after adjusting for blood cell counts. We replicated all 9 known loci and found an independent signal at CPOX near GPR15. In addition, we found 6 new loci at PRSS23, AVPR1B, PSEN2, LINC00299, RPS6KA2, and KIAA0087. Most of the lead probes (13 out of 15) associated with cigarette smoking, overlapped regions of open chromatin (FAIRE and DNaseI hypersensitive sites) or / and H3K27Ac peaks (ENCODE data set), which mark regulatory elements. The effect of smoking on DNA methylation was partially reversible upon smoking cessation for longer than 3 months. We report the first statistically significant interaction between a SNP (rs2697768) and cigarette smoking on DNA methylation (cg03329539). We provide evidence that the metSNP for cg03329539 regulates expression of the CHRND gene located circa 95 Kb downstream of the methylation site. Our findings suggest the existence of dynamic, reversible site-specific methylation changes in response to cigarette smoking , which may contribute to the extended health risks associated with cigarette smoking.
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