Background: Reticulated platelets (RP) are young, functionally active platelet forms which are detected by RNA staining. Their content in circulation reflects the intensity of thrombocytopoesis in the bone marrow.

Aims: In this study we assessed the relationships of RP content with platelet size and activity in healthy volunteers.

Methods: RP were evaluated by thiazole orange staining using flow cytometry, platelet size indexes included mean platelet volume (MPV), platelet large cell ratio (P-LCR) measured in a Coulter type analyzer and forward scattering (FSC) measured in a flow cytometer. Platelet activity was evaluated by expression of activated glycoprotein (GP) IIb-IIIa (PAC-1 antibody binding) and CD62P using flow cytometry. Platelets were activated by thrombin receptor activating peptide (TRAP) (10 and 1 µM) and ADP (20 and 2.5 µM).

Results: The percentage of RP in healthy volunteers varied from 2.9% to 23.8% (mean ± SD – 11.7 ± 4.7%, n = 99) and correlated with all platelet size indexes, MPV, P-LCR and FCS (r from 0.452 to 0.529, p < 0.001, n = 87-99). RP were distributed at a ratio 9:1 between 50% subpopulations of large and small platelets according to FSC index. Expression of activated GP IIb-IIIa correlated with RP percentage and platelet size indexes when platelets were activated by both doses of TRAP and ADP (r from 0.309 to 0.560, p from 0.014 to < 0.001, n = 50- 62). CD62P expression correlated with RP percentage and platelet size indexes when platelets were activated by 10 µM TRAP inducing maximal CD62P expression, (r from 0.332 to 0.556, p from 0.008 to < 0.001, n = 65), but not by weaker agonists, 1 µM TRAP and both ADP doses (r < 0.3, n = 54-66).

Conclusions: High RP content in healthy volunteers is associated with the increase of platelet size and activity in the whole platelet population

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/reticulated-platelets-in-healthy-volunteers-relationships-with-platelet-size-indexes-and-platelet-activity/