Targeting neutrophil extracellular trap accumulation under flow in patients with immune-mediated thrombotic thrombocytopenic purpura.

ABSTRACT: Neutrophil NETosis is a unique form of cell death, characterized by the release of decondensed chromatin and antimicrobial contents to the extracellular space, which is involved in inflammation and thrombosis. However, the role of NETosis in the pathogenesis of immune-mediated thrombotic thrombocytopenic purpura (iTTP) and how a targeted therapy affects the accumulation of neutrophil extracellular traps (NETs) under flow remain unknown. Flow cytometry demonstrated that the percentage of neutrophils undergoing NETosis in whole blood from patients with iTTP on admission was significantly increased, with a concurrent decrease in the capacity of inducible NETosis by shigatoxin. After therapy, the percentage of H3Cit+MPO+ neutrophils was significantly reduced, with an improvement in inducible NETosis in these patients. Additionally, little to no NET and thrombus formation was detected underflow in the whole blood from patients with iTTP when platelet counts were very low, but the NET and thrombus formation was dramatically increased following therapy when platelet counts rose to ≥50 × 109/L or were restored to normal with donor platelets. Similarly, there was no thrombus or NET accumulation under flow in the whole blood from vwf-/- mice, but NET accumulation was significantly higher in Adamts13-/- mice than in wild-type mice. Finally, recombinant ADAMTS13 or caplacizumab (or anfibatide) prevented NET and thrombus formation under flow in whole blood from patients with iTTP or from Adamts13-/- mice. These results indicate that neutrophil NETosis and NET formation depend on platelets and von Willebrand factor (VWF) in iTTP, and a targeted therapy such as recombinant ADAMTS13 or caplacizumab may prevent NET and thrombus formation under flow in iTTP.

Transfusion of cryopreserved packed red blood cells is safe and effective after trauma: a prospective randomized trial.

OBJECTIVES: To determine the safety and efficacy of cryopreserved packed red blood cell (CPRBC) transfusion in trauma patients. BACKGROUND: Liquid packed red blood cells (LPRBCs) have an abbreviated shelf-life and worsening storage lesion with age. CPRBCs are frozen 2 to 6 days after donation, stored up to 10 years, and are available for 14 days after thawing and washing. CPRBCs can be utilized in diverse settings, but the effect on clinical outcomes is unknown. METHODS: We performed a prospective, randomized, double-blind study at 5 level 1 trauma centers. Stable trauma patients requiring transfusion were randomized to young LPRBCs (≤14 storage days), old LPRBCs (>14 storage days), or CPRBCs. Tissue oxygenation (StO2), biochemical and inflammatory mediators were measured, and clinical outcomes were determined. RESULTS: Two hundred fifty-six patients with well-matched injury severity and demographics (P > 0.2) were randomized (84 young, 86 old, and 86 CPRBCs). Pretransfusion and final hematocrits were similar (P > 0.68). Patients in all groups received the same number of units postrandomization (2 [1-4]; P > 0.05). There was no difference in the change in tissue oxygenation between groups. CPRBCs contained less α2-macrogobulin, haptoglobin, C-reactive protein, and serum amyloid P (P < 0.001). Organ failure, infection rate, and mortality did not differ between groups (P > 0.2). CONCLUSIONS: Transfusion of CPRBCs is as safe and effective as transfusion of young and old LPRBCs and provides a mechanism to deliver PRBCs in a wide variety of settings.