Sex-specific associations between systolic, diastolic and pulse pressure and hemostatic parameters in the population-based KORA-Fit study: a cross-sectional study

Unfolded Von Willebrand Factor Binds Protein S and Reduces Anticoagulant Activity

Protein S (PS), the critical plasma cofactor for the anticoagulants tissue factor (TF) pathway inhibitor (TFPI) and activated protein C (APC), circulates in two functionally distinct pools: free (anticoagulant) or bound to complement component 4b-binding protein (C4BP) (anti-inflammatory). Acquired free PS deficiency is detected in several viral infections, but its cause is unclear. Here, we identified a shear-dependent interaction between PS and von Willebrand Factor (VWF) by mass spectrometry. Consistently, plasma PS and VWF comigrated in both native and agarose gel electrophoresis. The PS/VWF interaction was blocked by TFPI but not APC, suggesting an interaction with the C-terminal sex hormone binding globulin (SHBG) region of PS. Microfluidic systems, mimicking arterial laminar flow or disrupted turbulent flow, demonstrated that PS stably binds VWF as VWF unfolds under turbulent flow. PS/VWF complexes also localized to platelet thrombi under laminar arterial flow. In thrombin generation-based assays, shearing plasma decreased PS activity, an effect not seen in the absence of VWF. Finally, free PS deficiency in COVID-19 patients, measured using an antibody that binds near the C4BP binding site in SHBG, correlated with changes in VWF, but not C4BP, and with thrombin generation. Our data suggest that PS binds to a shear-exposed site on VWF, thus sequestering free PS and decreasing its anticoagulant activity, which would account for the increased thrombin generation potential. As many viral infections present with free PS deficiency, elevated circulating VWF, and increased vascular shear, we propose that the PS/VWF interaction reported here is a likely contributor to virus-associated thrombotic risk.

Testing and Evaluation of a Novel Hemostatic Matrix in a Swine Junctional Hemorrhage Model

INTRODUCTION

In an ongoing effort to improve survival and reduce blood loss from hemorrhagic injuries on the battlefield, new hemostatic dressings continue to be developed. This study aimed to determine the efficacy of a novel silicon dioxide-based hemostatic matrix (HM) and compare it with the current military standard Quikclot Combat Gauze (QCG) utilizing a lethal femoral artery injury model.

MATERIALS AND METHODS

The femoral arteries of 20 anesthetized swine were isolated, and an arteriotomy was performed. After a 45 s free bleed, the wound was treated with either HM or QCG (n = 10 per group). Following a 60-min observation period, ipsilateral leg manipulations and angiography were performed. Animal survival, hemostasis, blood loss, exothermic reaction, and femoral artery patency were analyzed.

RESULTS

Despite a volumetric size discrepancy between the two products tested, the survival rate was similar between the two groups (80% HM, 90% QCG, n = 10, P = 0.588). Immediate hemostasis was obtained in 50% of HM animals and 40% of QCG animals. There was no difference in total blood loss recorded between the two groups (P = 0.472). Femoral artery patency rates following ipsilateral leg manipulations were similar between the two groups (50% HM, 33% QCG, P = 0.637), with no contrast extravasation in HM-treated wounds (0% HM, 33% QCG, P = 0.206). There was no significant difference in either pretreatment or posttreatment laboratory values, and there were no exothermic reactions in either group.

CONCLUSIONS

The SiOxMed HM demonstrated comparable hemostatic efficacy to QCG. The tested form of HM may be appropriate for surgical or topical hemostasis applications, and with further product development, it could be used for battlefield trauma implementation.