A new look at an old body: molecular determinants of Weibel-Palade body composition and von Willebrand factor exocytosis.

Endothelial cells, forming a monolayer along blood vessels, intricately regulate vascular hemostasis, inflammatory responses, and angiogenesis. A key determinant of these functions is the controlled secretion of Weibel-Palade bodies (WPBs), which are specialized endothelial storage organelles housing a presynthesized pool of the hemostatic protein von Willebrand factor and various other hemostatic, inflammatory, angiogenic, and vasoactive mediators. This review delves into recent mechanistic insights into WPB biology, including the biogenesis that results in their unique morphology, the acquisition of intraluminal vesicles and other cargo, and the contribution of proton pumps to organelle acidification.

Quantitative super-resolution imaging of platelet degranulation reveals differential release of von Willebrand factor and von Willebrand factor propeptide from alpha-granules.

Background: Von Willebrand factor (VWF) and VWF propeptide (VWFpp) are stored in eccentric nanodomains within platelet alpha-granules. VWF and VWFpp can undergo differential secretion following Weibel-Palade body exocytosis in endothelial cells; however, it is unclear if the same process occurs during platelet alpha-granule exocytosis. Using a high-throughput 3-dimensional super-resolution imaging workflow for quantification of individual platelet alpha-granule cargo, we studied alpha-granule cargo release in response to different physiological stimuli.

Risk of SARS-CoV-2 transmission upon return to work in RNA-positive healthcare workers.

Background: Healthcare workers (HCWs) are at risk for coronavirus disease 2019 (COVID-19), and for spreading severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) amongst colleagues and patients.

Aim: To study the presence of SARS-CoV-2 RNA and possible onward transmission by HCWs upon return to work after COVID-19, and association with disease severity and development of antibodies over time.

Methods: Unvaccinated HCWs with positive SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) were recruited prospectively.