Abstract Number: PB1666
Meeting: ISTH 2020 Congress
Background: Newly formed platelets, also known as reticulated or immature platelets, have been clinically correlated with adverse cardiovascular outcomes. However, much of what is thought about young platelets is largely based upon indirect measures or follows a pathological insult.
Aims: To develop direct temporal labelling of platelets in mice in vivo to allow tracking and molecular phenotyping without the need to induce experimental thrombocytopenia.
Methods: Fluorescently conjugated antibodies (Emfret, Germany) were administered (i.v.) to C57BL/6 mice at specific timepoints, to label platelets. Fluorescence activated cell sorting was used to isolate platelets in blood samples and mRNA levels quantified by qPCR. Alternatively flow cytometry was used to track or assess platelets in blood samples. Whole blood ex vivo aggregation and in vivo arterial injury model were used to examine platelet function.
Results: Newly formed platelets (< 24 hours old) contained the greatest levels of mRNA and contributed disproportionately to thrombi forming ex vivo and in vivo. Consecutive sampling demonstrated that new platelets are heterogenous in size, with a similar size distribution to older populations, and that their average size does not change as they age. Finally, paired flow cytometric analysis revealed that expression of MHC1, PECAM-1 (CD31), GPV (CD42d), integrin α2 (CD49b) and GPVI significantly decreased as platelets aged. In contrast CD9 expression significantly increased.
Conclusions: Unlike approaches that induce pathophysiological insult such as thrombocytopaenia, our approach allows the study of platelets throughout a normal life span. Our observations confirm (mRNA content and function) and dispel (platelet size) certain commonly held beliefs. Our studies also indicate that loss of key receptors including PECAM1 and GPVI, with concurrent increase in CD9 may underpin changes in hemostatic function associated with the ageing platelet. Finally, this approach will provide further functional and molecular insights into how different platelet-age profiles contribute to health and disease.
To cite this abstract in AMA style:Armstrong P, Joshi A, Crescente M, Mayr M, Warner T. Direct Temporal Labelling of Platelets in vivo Allows Monitoring and Examination of Newly Formed and Aged Platelets to Reveal Changes in Receptor Expression Levels and Loss of Functional Ability [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/direct-temporal-labelling-of-platelets-in-vivo-allows-monitoring-and-examination-of-newly-formed-and-aged-platelets-to-reveal-changes-in-receptor-expression-levels-and-loss-of-functional-ability/. Accessed February 27, 2024.
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