| 1. |
- Connolly-Andersen, Anne-Marie, et al.
(author)
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Increased Thrombopoiesis and Platelet Activation in Hantavirus-Infected Patients
- 2015
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In: Journal of Infectious Diseases. - : Oxford University Press. - 0022-1899 .- 1537-6613. ; 212:7, s. 1061-1069
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Journal article (peer-reviewed)abstract
- Background. Thrombocytopenia is a common finding during viral hemorrhagic fever, which includes hemorrhagic fever with renal syndrome (HFRS). The 2 main causes for thrombocytopenia are impaired thrombopoiesis and/or increased peripheral destruction of platelets. In addition, there is an increased intravascular coagulation risk during HFRS, which could be due to platelet activation. Methods. Thrombopoiesis was determined by quantification of platelet counts, thrombopoietin, immature platelet fraction, and mean platelet volume during HFRS. The in vivo platelet activation was determined by quantification of soluble P-selectin (sP-selectin) and glycoprotein VI (sGPVI). The function of circulating platelets was determined by ex vivo stimulation followed by flow cytometry analysis of platelet surface-bound fibrinogen and P-selectin exposure. Intravascular coagulation during disease was determined by scoring for disseminated intravascular coagulation (DIC) and recording thromboembolic complications. Results. The levels of thrombopoietin, immature platelet fraction, and mean platelet volume all indicate increased thrombopoiesis during HFRS. Circulating platelets had reduced ex vivo function during disease compared to follow-up. Most interestingly, we observed significantly increased in vivo platelet activation in HFRS patients with intravascular coagulation (DIC and thromboembolic complications) as shown by sP-selectin and sGPVI levels. Conclusions. HFRS patients have increased thrombopoiesis and platelet activation, which contributes to intravascular coagulation.
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| 2. |
- Lopez-Alonso, Ana, et al.
(author)
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Individual Platelet Adhesion Assay: Measuring Platelet Function and Antiplatelet Therapies in Whole Blood via Digital Quantification of Cell Adhesion
- 2013
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In: Analytical Chemistry. - : American Chemical Society. - 0003-2700 .- 1520-6882. ; 85:13, s. 6497-6504
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Journal article (peer-reviewed)abstract
- Widespread monitoring of platelet function and the effect of antiplatelet drugs will improve outcomes in cardiovascular patients, but platelet function testing is not routine in clinical practice. We report a rapid, accurate methodology to quantify platelet-protein interactions: a microarray of contact-printed 6-mu m fibrinogen dots on a transparent substrate binds platelets from whole blood, one platelet per dot. The fractional occupancy of an array of fibrinogen dots after a predefined incubation time quantitatively assays platelet adhesion to the protein matrix. We demonstrate this technique by measurement of platelet adhesion to fibrinogen as a means to quantify the effect of the P2Y(12) and alpha IIb beta 3 receptor inhibitors cangrelor and abciximab, respectively, both in vitro-by incubating the drug with a freshly drawn blood sample-and in blood from patients treated with antiplatelet agents. The effects of single- and dual-antiplatelet therapy are also assessed. Results from this platelet-binding assay are well correlated with standard techniques including flow cytometry and light transmission aggregometry. This assay technology, readily integrated with microfluidic platforms, is generally applicable to the assay of cell-protein interactions and promises more effective, rapid assay of drug effects in cardiovascular disease patients.
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| 3. |
- Ramström, Sofia, 1973-, et al.
(author)
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Annexin V binding to platelets is agonist, time and temperature dependent
- 2010
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In: Platelets. - : Taylor & Francis. - 0953-7104 .- 1369-1635. ; 21:4, s. 289-296
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Journal article (peer-reviewed)abstract
- Platelets bind annexin V when stimulated with combinations of platelet agonists such as collagen and thrombin. Previous studies have demonstrated significant heterogeneity of platelets binding annexin V. The relative role of the thrombin protease-activated receptors (PARs), PAR1 and PAR4, together with different methods of platelet preparation on annexin V binding to platelets is unclear. We therefore investigated the role of PAR1- and PAR4-activating peptides in combination with collagen-related peptide on annexin V binding. In diluted whole blood, PAR1- and PAR4-activating peptides were as effective as thrombin in inducing annexin V binding. However, in washed platelets, PAR-activating peptides were less potent than thrombin at inducing annexin V binding. This difference was more pronounced when experiments were performed at 37 degrees C compared to room temperature. In studies of diluted whole blood, platelet rich plasma and washed platelets, platelets incubated at room temperature bound more annexin V than platelets incubated at 37 degrees C. We also saw a significant effect of time on annexin V binding, in that more annexin V bound to platelets with longer incubation times. In conclusion, PAR1 and PAR4-activating peptides were as effective as thrombin in inducing annexin V binding in combination with collagen-related peptide in diluted whole blood and platelet rich plasma, but not in washed platelets. In addition, incubation temperature and time has a strong influence on annexin V binding to platelets. Thus variations in these conditions may explain the differences observed between previous studies.
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| 4. |
- Tynngård, Nahreen, et al.
(author)
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High fragmentation in platelet concentrates impacts the activation, procoagulant, and aggregatory capacity of platelets
- 2023
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In: Platelets. - : Taylor & Francis. - 0953-7104 .- 1369-1635. ; 34:1
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Journal article (peer-reviewed)abstract
- Platelets are transfused to patients to prevent bleeding. Since both preparation and storage can impact the hemostatic functions of platelets, we studied platelet concentrates (PCs) with different initial composition in regard to platelet fragmentation and its impact on storage-induced changes in activation potential. Ten whole blood derived PCs were assessed over 7 storage days. Using flow cytometry, platelet (CD41+) subpopulations were characterized for activation potential using activation markers (PAC-1, P-selectin, and LAMP-1), phosphatidylserine (Annexin V), and mitochondrial integrity (DiIC1(5)). Aggregation response, coagulation, and soluble activation markers (cytokines and sGPVI) were also measured. Of the CD41+ events, the PCs contained a median of 82% normal-sized platelets, 10% small platelets, and 8% fragments. The small platelets exhibited procoagulant hallmarks (increased P-selectin and Annexin V and reduced DiIC1(5)). Normal-sized platelets responded to activation, whereas activation potential was decreased for small and abolished for fragments. Five PCs contained a high proportion of small platelets and fragments (median of 28% of CD41+ events), which was significantly higher than the other five PCs (median of 9%). A high proportion of small platelets and fragments was associated with procoagulant hallmarks and decreased activation potential, but, although diminished, they still retained some activation potential throughout 7 days storage.
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