platelet aggregates
Recently Published Documents


TOTAL DOCUMENTS

548
(FIVE YEARS 75)

H-INDEX

46
(FIVE YEARS 6)

2022 ◽  
Vol 23 (1) ◽  
pp. 493
Author(s):  
Gina Perrella ◽  
Samantha J. Montague ◽  
Helena C. Brown ◽  
Lourdes Garcia Quintanilla ◽  
Alexandre Slater ◽  
...  

Understanding the pathways involved in the formation and stability of the core and shell regions of a platelet-rich arterial thrombus may result in new ways to treat arterial thrombosis. The distinguishing feature between these two regions is the absence of fibrin in the shell which indicates that in vitro flow-based assays over thrombogenic surfaces, in the absence of coagulation, can be used to resemble this region. In this study, we have investigated the contribution of Syk tyrosine kinase in the stability of platelet aggregates (or thrombi) formed on collagen or atherosclerotic plaque homogenate at arterial shear (1000 s−1). We show that post-perfusion of the Syk inhibitor PRT-060318 over preformed thrombi on both surfaces enhances thrombus breakdown and platelet detachment. The resulting loss of thrombus stability led to a reduction in thrombus contractile score which could be detected as early as 3 min after perfusion of the Syk inhibitor. A similar loss of thrombus stability was observed with ticagrelor and indomethacin, inhibitors of platelet adenosine diphosphate (ADP) receptor and thromboxane A2 (TxA2), respectively, and in the presence of the Src inhibitor, dasatinib. In contrast, the Btk inhibitor, ibrutinib, causes only a minor decrease in thrombus contractile score. Weak thrombus breakdown is also seen with the blocking GPVI nanobody, Nb21, which indicates, at best, a minor contribution of collagen to the stability of the platelet aggregate. These results show that Syk regulates thrombus stability in the absence of fibrin in human platelets under flow and provide evidence that this involves pathways additional to activation of GPVI by collagen.


Author(s):  
Catherine J Layssol-Lamour ◽  
Fanny A Granat ◽  
Ambrine M Sahal ◽  
Jean-Pierre D Braun ◽  
Catherine Trumel ◽  
...  

Nonterminal blood sampling in laboratory mice is a very common procedure. With the goal of improving animal welfare, different sampling sites and methods have been compared but have not achieved a consensus. Moreover, most of these studies overlooked the quality of blood specimens collected. The main preanalytical concern with EDTA-treated blood specimens for hematology analyses is platelet aggregation, which is known to cause analytical errors. Our objective was to find a nonterminal blood sampling method with minimal adverse effects on mice and few or no platelet aggregates. We tested and compared 2 collection sites, 4 sampling methods, and 3 antithrombotic drugs in 80 C57BL6/j male and female mice by evaluating platelet aggregates on blood smears and platelet, WBC, and RBC counts. In addition, the blood collection process was carefully evaluated, and adverse effects were recorded. Platelet aggregation was lower in specimens collected from the jugular vein than from the facial vein, with no effect of the sampling device or the presence of an antithrombotic additive. Highly aggregated specimens were significantly associated with lower platelet counts, whereas aggregation had no effect on WBC or RBC counts. Adverse events during sampling were significantly associated with more numerous platelet aggregates. The jugular vein is thus a satisfactory sampling site in mice in terms of both animal welfare and low platelet aggregation. Using antithrombotic agents appears to be unnecessary, whereas improving sampling conditions remains a key requirement to ensure the quality of EDTA-treated blood specimens from mice.


Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3414
Author(s):  
Sarah Nasreen Schmidt ◽  
Wilfried Reichardt ◽  
Beat A. Kaufmann ◽  
Carolin Wadle ◽  
Dominik von Elverfeldt ◽  
...  

Previous mouse studies have shown the increased presence of platelets in the myocardium during early stages of myocarditis and their selective detection by MRI. Here, we aimed to depict early myocarditis using molecular contrast-enhanced ultrasound of activated platelets, and to evaluate the impact of a P2Y12 receptor platelet inhibition. Experimental autoimmune myocarditis was induced in BALB/c mice by subcutaneous injection of porcine cardiac myosin and complete Freund adjuvant (CFA). Activated platelets were targeted with microbubbles (MB) coupled to a single-chain antibody that binds to the “ligand-induced binding sites” of the GPIIb/IIIa-receptor (=LIBS-MB). Alongside myocarditis induction, a group of mice received a daily dose of 100 g prasugrel for 1 month. Mice injected with myosin and CFA had a significantly deteriorated ejection fraction and histological inflammation on day 28 compared to mice only injected with myosin. Platelets infiltrated the myocardium before reduction in ejection fraction could be detected by echocardiography. No selective binding of the LIBS-MB contrast agent could be detected by either ultrasound or histology. Prasugrel therapy preserved ejection fraction and significantly reduced platelet aggregates in the myocardium compared to mice without prasugrel therapy. Therefore, P2Y12 inhibition could be a promising early therapeutic target in myocarditis, requiring further investigation.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Masako Nishikawa ◽  
Hiroshi Kanno ◽  
Yuqi Zhou ◽  
Ting-Hui Xiao ◽  
Takuma Suzuki ◽  
...  

AbstractA characteristic clinical feature of COVID-19 is the frequent incidence of microvascular thrombosis. In fact, COVID-19 autopsy reports have shown widespread thrombotic microangiopathy characterized by extensive diffuse microthrombi within peripheral capillaries and arterioles in lungs, hearts, and other organs, resulting in multiorgan failure. However, the underlying process of COVID-19-associated microvascular thrombosis remains elusive due to the lack of tools to statistically examine platelet aggregation (i.e., the initiation of microthrombus formation) in detail. Here we report the landscape of circulating platelet aggregates in COVID-19 obtained by massive single-cell image-based profiling and temporal monitoring of the blood of COVID-19 patients (n = 110). Surprisingly, our analysis of the big image data shows the anomalous presence of excessive platelet aggregates in nearly 90% of all COVID-19 patients. Furthermore, results indicate strong links between the concentration of platelet aggregates and the severity, mortality, respiratory condition, and vascular endothelial dysfunction level of COVID-19 patients.


TH Open ◽  
2021 ◽  
Author(s):  
Diana Adrienne Gorog ◽  
J. Yamamoto

Herein, we set out a rebuttal to the publication by Claveria and co-workers published in TH Open this month entitled “Global Thrombosis Test: Occlusion by Coagulation or SIPA?” We strongly believe that the conclusions of their paper, suggesting that occlusion (OT) in the Global Thrombosis Test (GTT) is due to coagulation, rather than shear-induced platelet thrombus formation, is incorrect and the evidence and arguments they present are fundamentally flawed, with major errors both in the experimental approach and in the interpretations of the results. The evidence which they demonstrate, shows that occlusion in the GTT is, in fact, caused by high shear induced platelet thrombus formations. We set out herein the evidence for that, based on histology of the thrombus from the GTT in earlier work using electron microscopy showing large platelet aggregates, the very brief timescale of OT in the GTT compared to coagulation time and the sensitivity of the OT in the GTT to the effects of heparin, t-PA and P2Y12 inhibitors. In addition, we revisit the known pathomechanism of high shear-mediated platelet aggregation to underpin our rationale and show that the modifications to the instrument proposed by Claveria and co-authors would render the technique unphysiological. We highlight several methodological concerns and apparent misinterpreted of the data obtained. We present evidence predominantly from the authors’ own data, together with our earlier published data and evidence from the literature, showing that occlusion in the GTT occurs do to shear-induced platelet aggregation.


Author(s):  
Dijana Šefer ◽  
Predrag Miljić ◽  
Nada Kraguljac‐Kurtović ◽  
Sandra Bižić‐Radulović ◽  
Andrija Bogdanović ◽  
...  

Author(s):  
Silke Zimmermann ◽  
Martin Federbusch ◽  
Berend Isermann ◽  
Shrey Kohli

Vaccine-induced thrombotic thrombocytopenia (VITT) is a thrombotic complication mimicking heparin induced thrombocytopenia (HIT). This very rare but severe thrombotic complication occurs post vaccination against SARS-Cov-2. Diagnosis of VITT remains challenging, but a current consensus report suggests a 10-point guideline for early detection of VITT, which should be confirmed by PF-4 immunoassays. The latter is considered to be the most reliable diagnostic test. We observed platelet aggregates and increased platelet volume in patients with VITT in routine blood smear analyses. These routine blood analytic findings may – together with the clinical presentation – support and speed up the diagnosis of VITT, and may be of particular importance in low-income countries with limited access to PF-4 immunoassays.


2021 ◽  
Author(s):  
Beng Chong ◽  
Halina Leung ◽  
Jose Perdomo ◽  
Zohra Ahmadi ◽  
Fairooj Rashid ◽  
...  

Abstract Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare yet serious adverse effect of adenoviral vector vaccines (AstraZeneca and Johnson & Johnson) against COVID-191. Anti-platelet factor 4 (PF4) antibodies are present in VITT patients2,3. Although the current view suggests that platelet activation by anti-PF4 antibodies is the cause of thrombosis there is as yet no direct evidence that the antibodies induce clot formation and thrombocytopenia (reduction in platelet counts) in VITT and the mechanisms involved remain unknown4. Here we show that VITT antibodies induce thrombosis and thrombocytopenia, and that thrombus formation is mediated by neutrophil extracellular traps (NETs). We found markers of NETosis, abundance of neutrophil/platelet aggregates and presence of neutrophils undergoing NETosis in patients with active VITT. VITT antibodies directly stimulate neutrophils to release NETs and induce thrombus formation containing abundant platelets, neutrophils, fibrin, extracellular DNA and citrullinated histone H3 using an in vitro blood flow microfluidic system. In transgenic mice expressing human PF4 and FcγRIIa, VITT antibodies lead to thrombosis, thrombocytopenia and formation of low density granulocytes. Pharmacological and genetic inhibition of NETosis prevents VITT-induced thrombosis in mice but not thrombocytopenia. In contrast, in vivo blockage of FcγRIIa abrogates both thrombosis and thrombocytopenia suggesting they are distinct processes. Our findings indicate that VITT antibodies activate cells via FcγRIIa and are responsible for thrombosis and thrombocytopenia. This study identifies NETosis as a pathogenic mechanism for thrombus formation in VITT. We anticipate our findings will motivate future development of NETosis and FcγRIIa inhibitors as potential specific therapies for VITT and consequently better patient outcomes.


2021 ◽  
Vol 10 (18) ◽  
pp. 4190
Author(s):  
Parnian Alavi ◽  
Abhisha M. Rathod ◽  
Nadia Jahroudi

Endothelial cells that cover the lumen of all blood vessels have the inherent capacity to express both pro and anticoagulant molecules. However, under normal physiological condition, they generally function to maintain a non-thrombogenic surface for unobstructed blood flow. In response to injury, certain stimuli, or as a result of dysfunction, endothelial cells release a highly adhesive procoagulant protein, von Willebrand factor (VWF), which plays a central role in formation of platelet aggregates and thrombus generation. Since VWF expression is highly restricted to endothelial cells, regulation of its levels is among the most important functions of endothelial cells for maintaining hemostasis. However, with aging, there is a significant increase in VWF levels, which is concomitant with a significant rise in thrombotic events. It is not yet clear why and how aging results in increased VWF levels. In this review, we have aimed to discuss the age-related increase in VWF, its potential mechanisms, and associated coagulopathies as probable consequences.


Sign in / Sign up

Export Citation Format

Share Document