PB0890 - Discrimination of agonists-stimulated platelet phenotypes depending on pathogen inactivation and storage temperature in a blood bank

Background: Platelets accumulate lesions over their life (in vivo) and their storage duration (ex vivo). The choice of the processing and storage conditions by blood centers influences platelet characteristics: platelet concentrates (PCs) going through a pathogen inactivation treatment (PIT), or a 4°C-storage will, each in their own way, modify the functions and phenotypes of platelets.

Aims: In-vitro functionality tests are primordial to understand the impact on patients of the above-mentioned alterations. We set up an innovative flow cytometry characterization of platelet function, mapping their phenotype upon stimulation by different agonists. Both the effects of PIT and storage temperature were evaluated.

Methods: Based on a pool-&-split approach, four conditions (PIT or not, 22 or 4°C) up to 14 days of storage were evaluated. Platelet functions were analyzed using the combination of platelet surface expressions: CD42b(+/-), Lactadherin(+/-), CD62P(+/-) and PAC-1(+/-) at baseline (with or without Ca2+Mg2+) or after activation (ADP, TRAP-6, Convulxin) and under different incubation temperatures (either 22 or 37°C).

Results: After 7 days of storage at 4°C (Fig.1 C-D), regardless of which agonist was added, the population of aggregatory phenotype (CD42b+/Lactadherin-/CD62P+/PAC-1+) decreased and privileged a more secretory platelet population (CD42b+/Lactadherin-/CD62P+/PAC-1-) compared with 22°C-stored platelets (Fig.1 A-B). Furthermore, PIT-4°C PCs also revealed a higher activation capacity, as procoagulant (CD42b+/Lactadherin+/CD62P+/PAC-1-) and secretory populations appeared just with the addition of Ca2+Mg2+ (Fig.1 D).

Conclusion(s): Our results revealed a clear difference in platelet subset composition and activation behavior following stimulation between storage conditions. A change on activation phenotype was observed following the PIT and the 4°C-Storage. 14-day-storage data will be presented and discussed with other platelet functions and proteomic data.
Finally, platelet heterogeneity phenotypes after stimulation or not, might be essential to understand the platelet function. 4°C-stored platelets is a promising development field, and such methods could help characterizing the mechanisms involved during storage and the potential clinical impacts.