Weibel-Palade Bodies

Definition/Introduction

Weibel-Palade bodies are small storage granules found in endothelial cells located in the intima of the heart and blood vessels. They are found in arteries, capillaries, veins, and the endocardium but are notably absent in lymphatic vessels. These bodies primarily store 2 key molecules—P-selectin and von Willebrand factor (vWF)—which have important roles in inflammation and hemostasis.

vWF is essential for blood coagulation,[1] and it binds to coagulation factor VIII in the presence of vessel injury and cross-links the basement membrane collagen of the vessel to glycoprotein Ib (gpIb) on platelets. This process of platelet adhesion is one of the initial steps in clot formation and maturation. P-selectin significantly increases the permeability of endothelial cells, allowing components of the cell-mediated immune system, such as leukocytes, to roll, marginate, and infiltrate the site of inflammation. Additionally, P-selectin contributes to platelet aggregation, as it is activated and incorporated into the cell membrane by thrombin.[1]

Many other protein molecules are stored in Weibel-Palade bodies, including interleukin 8, endothelin 1, eotaxin-3, osteoprotegerin, angiopoietin-2, and alpha-1,3-fucosyltransferase VI. These proteins serve as mediators of inflammation, immune response, angiogenesis, and regulation of vessel caliber in response to stressors.

Weibel-Palade bodies synthesize and assemble these protein molecules in the Golgi complex. Immature Weibel-Palade bodies are typically located near the cell nucleus, where they acquire most membrane proteins. As they mature, the Weibel-Palade bodies disperse along microtubules. Over time, Weibel-Palade bodies may also diffuse with one another to form larger congregations.

Issues of Concern