Platelet transfusion became an indispensable therapy in the modern medicine. Although the clinical advantage of platelet transfusion is well established, adverse reactions upon transfusion, especially transmission of bacterial infection, still represent a major challenge. While bacterial contamination is favored by the storage of platelets at room temperature, cold storage may represent a solution for this clinically relevant issue. In this study, we aimed to elucidate whether plasma has protective or detrimental effects on cold-stored platelets. We investigated the impact of different residual plasma contents in apheresis-derived platelet concentrates, stored at 4°;C or room temperature, on platelet function and survival. We found that platelets stored at 4°C have higher expression of apoptosis marker compared to room temperature-stored platelets leading to an accelerated clearance from the circulation in a humanized animal model. While cold-induced apoptosis was independent of the residual plasma concentration, cold storage was associated with better adhesive properties and higher response to activators. Of note, delta granule-related functions, such as ADP-mediated aggregation and CD63 release, were better preserved at 4°C especially in 100% plasma. An extended study to assess cold-stored platelet concentrates produced under standard care GMP conditions showed that platelet function, metabolism and integrity were better compared to those stored at room temperature. Taken together, our results show that residual plasma concentration does not have a cardinal impact on the cold storage lesions of apheresis-derived platelet concentrates and indicate that the current generation of additive solutions is suitable substitutes for plasma to store platelets at 4°C.

Life-threatening thrombotic events at unusual sites have been reported after vector-based vaccinations against severe acute respiratory syndrome coronavirus 2. This phenomenon is now termed vaccine-induced immune thrombotic thrombocytopenia (VITT). The pathophysiology of VITT is similar to that of heparin-induced thrombocytopenia (HIT) and is associated with platelet-activating antibodies (Abs) against platelet factor 4 (PF4). Therefore, current guidelines suggest nonheparin anticoagulants to treat VITT patients. In this study, we investigated the interactions of heparin, danaparoid, fondaparinux, and argatroban with VITT–Ab/PF4 complexes using an ex vivo model for thrombus formation as well as in vitro assays to analyze Ab binding and platelet activation. We found that immunoglobulin Gs (IgGs) from VITT patients induce increased adherent platelets/thrombus formation in comparison with IgGs from healthy controls. In this ex vivo flow-based model, the procoagulant activity of VITT IgGs was effectively inhibited with danaparoid and argatroban but also by heparin. Interestingly, heparin and danaparoid not only inhibited IgG binding to PF4 but were also able to effectively dissociate the preformed PF4/IgG complexes. Fondaparinux reduced the in vitro generation of procoagulant platelets and thrombus formation; however, it did not affect platelet aggregation. In contrast, argatroban showed no effect on procoagulant platelets and aggregation but significantly inhibited VITT-mediated thrombus formation. Taken together, our data indicate that negatively charged anticoagulants can disrupt VITT–Ab/PF4 interactions, which might serve as an approach to reduce Ab-mediated complications in VITT. Our results should be confirmed, however, in a clinical setting before a recommendation regarding the selection of anticoagulants in VITT patients could be made.

No abstract

Background and objectives Platelet transfusion is a standard medical therapy used to treat several bleeding disorders. However, a critical drawback is the dependency on donor-derived platelets, which leads to concerns like insufficient availability and immunological complications. In vitro platelet production from hematopoietic progenitor cells (CD34) may represent a reasonable solution.Materials and methods CD34+ cells were isolated from either buffy coat or peripheral blood and compared in terms of platelet production in vitro. The number and the quality of magnetically isolated CD34+ cells and their capability to differentiate into mature megakaryocytes were investigated using flow cytometry. Additionally, the functionality of megakaryocytes in term of in vitro platelet production was tested.Results Similar purity and quantity of CD34+ cells was found after their isolation from both cell sources. In contrast, after 6 days of culture, enhanced number of CD34+ cells isolated from buffy coat compared with peripheral blood was observed (5Á3 x 106 vs. 3Á0 x 106, respectively). Interestingly, despite a comparable nuclear maturation phenotype, the yield of platelets released from buffy coatderived megakaryocytes was significantly higher than from peripheral blood cells (platelet yield pro MK: 7Á2 vs. 2Á7, respectively). Importantly, platelets produced from buffy coat-derived cells could be activated by agonists.Conclusion Haematopoietic progenitor cells isolated from buffy coat have increased yield of platelets released from mature megakaryocytes and enhanced in vitro functionality, compared with peripheral blood-derived cells. Our study, suggests that buffy coat, obtained during blood donation processing, might be a promising source of megakaryocytes for in vitro platelet production.

No abstract