We demonstrate mechanochemical regulation of platelet adhesion to von Willebrand factor in thrombosis and hemostasis.

Key Points: ERp5, like its family members PDI and ERp57, accumulates at sites of vessel wall injury. Both platelets and endothelium secrete ERp5 on activation and contribute ERp5 necessary for thrombus formation in vivo.

Microfluidic devices have an established role in the study of platelets and coagulation factors in thrombosis, with potential diagnostic applications. However, few microfluidic devices have assessed the contribution of neutrophils to thrombus formation, despite increasing knowledge of neutrophils’ importance in cardiovascular thrombosis. We describe a thromboinflammation model which uses straight channels, lined with fixed human umbilical vein endothelial cells, after treatment with tumour necrosis factor-alpha. Re-calcified whole blood is perfused over the endothelium at venous and arterial shear rate. Neutrophil adhesion, platelet and fibrin thrombus formation, is measured over time by the addition of fluorescent antibodies to a whole blood sample. Fixed endothelium retains surface expression of adhesion molecules ICAM-1 and E-Selectin. Neutrophils adhere preferentially to platelet thrombi on the endothelium. Inhibitors of neutrophil adhesion and anti-inflammatory agents, such as isoquercetin, decrease neutrophil adhesion. Our model offers the advantage of the use of (1) fixed endothelium, (2) whole blood, instead of isolated neutrophils, and (3) a small amount of blood (1 mL). The characteristics of this thromboinflammation model provide the potential for further development for drug screening and point-of-care applications.

Peripheral artery disease (PAD) is caused by blocked arteries due to atherosclerosis and/or thrombosis which reduce blood flow to the lower limbs. It results in major morbidity, including ischemic limb, claudication, and amputation, with patients also suffering a heightened risk of heart attack, stroke, and death. Recent studies suggest women have a higher prevalence of PAD than men, and with worse outcomes after intervention. In addition to a potential unconscious bias faced by women with PAD in the health system, with underdiagnosis, and lower rates of guideline-based therapy, fundamental biological differences between men and women may be important. In this review, we highlight sexual dimorphisms in endothelial cell functions and how they may impact PAD pathophysiology in women. Understanding sex-specific mechanisms in PAD is essential for the development of new therapies and personalized care for patients with PAD.

Vaccine‐induced thrombotic thrombocytopenia (VITT) is a rare complication of adenovirus‐based vaccines aimed to prevent and minimize COVID‐19 and related pathophysiology. To describe patterns of testing for anti‐platelet factor 4 (PF4) antibodies using various ELISA assays in a large Australian cohort and comparative functional platelet activation assays in a subset. Asserachrom HPIA IgG ELISA was performed in 1284 patients over a period of 12 months, supplemented in select cohorts by comparative ELISA using three other methods (n = 78–179), three different functional assays (flow cytometry, serotonin release assay, and/or Multiplate; n = 476), and rapid immunological chemiluminescence anti‐PF4 assay (n = 460), in a multicenter study. For first episode presentations, 190/1284 (14.8%) ELISA tests were positive. Conversely, most (445/460; 96.7%) chemiluminescence anti‐PF4 test results were negative. All functional assays showed associations of higher median ELISA optical density with functional positivity and with high rates of ELISA positivity (64.0% to 85.2%). Data also identified functional positivity in 14.8%–36.0% of ELISA negative samples, suggesting false negative VITT by HPIA IgG ELISA in upward of one third of assessable cases. To our knowledge, this is the largest multicenter evaluation of anti‐PF4 testing for investigation of VITT. Discrepancies in test results (ELISA vs. ELISA or ELISA vs. functional assay) in some patients highlighted limitations in relying on single methods (ELISA and functional) for PF4 antibody detection in VITT, and also highlights the variability in phenotypic test presentation and pathomechanism of VITT.