| 1. |
- Tynngård, Nahreen, 1976-, et al.
(author)
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Variation in activation marker expression within the platelet population - a new parameter for evaluation of platelet flow cytometry data
- 2022
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In: Platelets. - : Taylor & Francis Group. - 0953-7104 .- 1369-1635. ; 33:8, s. 1113-1118
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Journal article (peer-reviewed)abstract
- In flow cytometry, individual cells are investigated. Platelet activation is normally reported in form of percentage of platelets expressing the marker (positive platelets) and/or mean/median fluorescence intensity (MFI) for the entire analyzed population. None of these take into account the variance of the marker expression between individual platelets. This can be obtained as data on coefficient of variation (CV). This study explores if CV provides additional information regarding platelet function. Samples from platelet concentrates (PCs) prepared by apheresis- (n = 13) and interim platelet unit (IPU) technique (n = 26) and stored for 6-7 days were included and compared. Spontaneous- and agonist-induced expression of activation markers (fibrinogen binding and exposure of P-selectin, LAMP-1, and CD63) was investigated as percentage positive platelets, MFI and CV. Spontaneous expression of P-selectin as percentage positive platelets and MFI was higher for IPU PCs than apheresis PCs, which in contrast had higher agonist-induced activation. CV for spontaneous fibrinogen binding and P-selectin exposure was larger for apheresis PCs, while IPU PCs generally had larger CV for P-selectin, LAMP-1, and CD63 after agonist stimulation. Our findings show that CV adds additional information when assessing platelet activation by providing data on the variation in activation responses within the platelet population.
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| 2. |
- 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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