Venous thromboembolism (VTE) is the third leading cardiovascular cause of death and is conventionally treated with anticoagulants that directly antagonize coagulation. However, recent data have demonstrated that also platelets play a crucial role in VTE pathophysiology. In the current review, we outline how platelets are involved during all stages of experimental venous thrombosis. Platelets mediate initiation of the disease by attaching to the vessel wall upon which they mediate leukocyte recruitment. This process is referred to as immunothrombosis, and within this novel concept inflammatory cells such as leukocytes and platelets directly drive the progression of VTE. In addition to their involvement in immunothrombosis, activated platelets can directly drive venous thrombosis by supporting coagulation and secreting procoagulant factors. Furthermore, fibrinolysis and vessel resolution are (partly) mediated by platelets. Finally, we summarize how conventional antiplatelet therapy can prevent experimental venous thrombosis and impacts (recurrent) VTE in humans.

Platelet concentrate (PC) transfusion seeks to provide haemostasis in patients presenting severe central thrombocytopenia or severe bleeding. PCs may induce adverse reactions (AR) that can occasionally be severe (SAR). PCs contain active biomolecules such as cytokines and lipid mediators. The processing and storage of PCs creates so-called structural and biochemical storage lesions that accumulate when blood products reach their shelf life. We sought to investigate lipid mediators as bioactive molecules of interest during storage and review associations with adverse reactions post-transfusion. To facilitate understanding, we focused on single donor apheresis (SDA) PCs with approximately 31.8% of PCs being delivered in our setting. Indeed, pooled PCs are the most widely transfused products, but the study of a single donor lipid mediator is easier to interpret. We are investigating key lipid mediators involved in AR. Adverse reactions were closely monitored in accordance with current national and regional haemovigilance protocols. Residual PCs were analysed post-transfusion in a series of observations, both with and without severe reactions in recipients. A decrease in the lysophosphatidylcholine species to produce the lysophosphatidic acid species has been observed during storage and in the case of AR. Lysophosphatidic acid increased with primarily platelet-inhibitor lipids. Anti-inflammatory platelet-induced inhibition lipids were weakly expressed in cases of severe adverse reactions. We therefore propose that a decrease in lysophosphatidylcholine and an increase in lysophosphatidic acid can prospectively predict serious adverse transfusion reactions.

Platelet concentrates (PCs) intended for transfusion contain bioactive molecules that can be considered Biological Response Modifiers (BRMs), mainly originating from plasma regardless of the preparation process. During storage, NGAL and GDF-15 levels increase in single donor apheresis platelet concentrates (SDA-PC), whereas in buffy coat platelet concentrates (BC-PC), the levels of MIP1α, MCP-3, and HSAA increase, and GDF-15 levels decrease. These molecules, primarily released by leukocytes, may contribute to adverse reactions (ARs) following a PC transfusion. Notably, in SDA-PC or BC-PC transfusions that result in ARs, the levels of NGAL, HSAA, and GDF-15 are significantly elevated, while the levels of MDC and CX3CL1 are significantly reduced compared to transfusions without ARs. These biomarkers could potentially serve as predictors for PCs-induced ARs.

The aging population often faces health issues that sometimes necessitate transfusions. Transfusion services are increasingly concerned about the rising number of transfusions and the aging donor population, as both factors are crucial in maintaining the quality of blood donations. In this context, our study aims to measure the bioactive molecule cytokine levels in single donor apheresis platelet concentrates (SDA-PC) based on the donor’s age and to determine whether these cytokines, in conjunction with the donor age, could contribute to transfusion adverse reactions (AR). Our findings indicate that well-known platelet molecules such as sCD62P, as well as IL-13, ADAMTS13, MIP-1α, NGAL, MCP-3, HSAA, GDF-15, CX3CL1, and MDC, were present in SDA-PC. Levels of MIP-1α, GDF-15, and sCD62P increased with donor aging, whereas levels of MDC decreased. In conclusion, most of the cytokine levels detected were elevated in cases of AR and with increasing donor age. Notably, GDF-15 was the only cytokine that showed a positive correlation with age in the context of AR.