WPBs and α-granules: More and more look-alike?

Abstract

In this issue of Blood, Streetley et al have used live-cell imaging and highresolution cryo-electron microscopy tomography to identify CD63+ luminal membrane vesicles in Weibel-Palade bodies (WPBs) in human umbilical vein endothelial cells (HUVECs) and microvascular endothelial cells. In response to an increase in intracellular calcium or cyclic adenosine monophosphate, these membranes are released as so-called exosomes in a fashion similar to that described for platelets and other cells. This is the first report of the presence of intraluminal vesicles (ILVs) in WPBs and the regulated release of exosomes from vasculature endothelial cells.