Von Willebrand factor: structure, properties and role in the process of hemostasis
Authors:   SI «Institute of Blood Pathology and Transfusion Medicine, NAMS of Ukraine», Shurko N 
Published: February 2021

The article reviews the scientific papars on the structure, function and biological role of von Willebrand factor (vWF). The vWF mainly was considered as the main factor in the development of bleeding disorders (von Willebrand’s disease). On the other hand, it can be able the cause thrombotic complications through to the functional ability of the factor to stimulate platelet adhesion. The aim of this work was to conduct an analysis of the structure of the factor, its role in the process of hemostasis to determine a border between two opposing processes. Von Willebrand factor is a hemostatic, multimeric glycoprotein, one of the key components of the hemostasis system, taking an active part at startup mechanisms of platelet adhesion at the site of vesselendothelial damage. On the other hand, another important function of vWF is co-factor activity related to coagulation factor VIII (FVIII), which is to stabilize its activity, promoting thrombin activation and preventing the cleavage of the molecule by blood plasma proteinases. The human gene of vWF is localized on the short arm of the 12 chromosome, contains 52 exons and covers approximately 180 kb. VWF is made by endothelial cells and by bone marrow megakaryocytes. The factor is preserved in the Weibel-Palade bodies of endotolial cells and α-granules of platelets. The primary pro-polypeptide consists of 2813 amino acid, of which 2050 form the mature peptide. The molecular weight of vWF is 220 kDa. In bloodstreamv WF circulates as a multimeric protein with a molecular weight from 400 to 20,000 kDa. The synthesized molecule has the next domain structure: D1-D2-D’-D3-A1-A2-A3-D4-C1-C2-C3-C4-C5-C6-CK. Domains are responsible for binding various proteins, including FVIII, fibrin, collagen, heparin, complement components etcetra. Von Willebrand disease (vWD) is the most common autosomal inherited disorder of the hemostasis system (from 0.6 to 2.0% of the population) and the cause is a genetic deficiency of quantitative and/or qualitative abnormal multimeric structure of the vWF molecule. There are three main subtypes of vWD. Quite often in such patients there is a decrease in FVIII activity, as an indirect consequence of changes in vWF. The basic principle of vWD treatment is based on the normalization of vWF and/or FVIII levels by increasing the level of external vWF under the action of desmopressin or the introduction of factor concentrates. In contrast to hereditary vWD, acquired von Willebrand syndrome is a relatively rare acquired bleeding of the blood coagulation system (incidence from 0.04 to 0.13 %) associated with various underlying diseases. For today a significant amount of research devoted to the relationship between vWF and thrombotic complications, that is due functional ability of the factor stimulate platelet adhesion. In particular, there are reports of the following complications in: pneumonia caused by Streptococcus pneumoniae; COVID-19; polycythemia vera; chronic kidney disease etcetra.