Stasis Promotes Erythrocyte Adhesion to von Willebrand Factor.

Objective: Venous thromboembolism is a major contributor to global disease burden. Leukocytes and platelets initiate thrombogenesis on blood stasis and initiate the formation of a fibrin, VWF (von Willebrand factor), and neutrophil extracellular trap scaffold for erythrocytes. However, there is little knowledge on how erythrocytes become stably incorporated into this scaffold.

Content delivery to newly forming Weibel-Palade bodies is facilitated by multiple connections with the Golgi apparatus.

Weibel-Palade bodies (WPBs) comprise an on-demand storage organelle within vascular endothelial cells. It's major component, the hemostatic protein von Willebrand factor (VWF), is known to assemble into long helical tubules and is hypothesized to drive WPB biogenesis. However, electron micrographs of WPBs at the Golgi apparatus show that these forming WPBs contain very little tubular VWF compared with mature peripheral WPBs, which raises questions on the mechanisms that increase the VWF content and facilitate vesicle growth.

Correlative light microscopy and electron tomography to study Von Willebrand factor exocytosis from vascular endothelial cells.

Revealing the ultrastructure and function of fluorescently labeled cellular components by correlative light and electron microscopy (CLEM) facilitates the study of structure-function relationships in complex biological processes. Given the diversity of available fluorescent tags, light microscopy is ideal for monitoring dynamic cellular processes, while electron microscopy reveals the morphological context of structures at high resolution. Endothelial cells lining the blood vessel wall contain storage organelles called Weibel-Palade bodies (WPBs), which contain tubules of densely packed helical spirals of the blood coagulation protein Von Willebrand factor (VWF).

Storage and secretion of naturally occurring von Willebrand factor A domain variants.

Von Willebrand disease (VWD) is a bleeding disorder characterized by reduced plasma von Willebrand factor (VWF) levels or functionally abnormal VWF. Low VWF plasma levels in VWD patients are the result of mutations in the VWF gene that lead to decreased synthesis, impaired secretion, increased clearance or a combination thereof. However, expression studies of variants located in the A domains of VWF are limited.

Factor VIII alters tubular organization and functional properties of von Willebrand factor stored in Weibel-Palade bodies.

In endothelial cells, von Willebrand factor (VWF) multimers are packaged into tubules that direct biogenesis of elongated Weibel-Palade bodies (WPBs). WPB release results in unfurling of VWF tubules and assembly into strings that serve to recruit platelets. By confocal microscopy, we have previously observed a rounded morphology of WPBs in blood outgrowth endothelial cells transduced to express factor VIII (FVIII).

Multigranular exocytosis of Weibel-Palade bodies in vascular endothelial cells.

Regulated exocytosis of Weibel-Palade bodies (WPBs) is a pivotal mechanism via which vascular endothelial cells initiate repair in response to injury and inflammation. Several pathways have been proposed to enable differential release of bioactive molecules from WPBs under different pathophysiologic conditions. Due to the complexity, many aspects of WPB biogenesis and exocytosis are still poorly understood.