Von Willebrand factor (VWF), encoded by the Vwf gene, is a large adhesive multimeric glycoprotein. It plays a crucial role in hemostasis, bridging platelets to the subendothelial matrix after vessel damage and thus regulating the balance between blood clotting and bleeding [2,3]. Aberrant regulation of VWF can lead to diseases ranging from bleeding disorders like von Willebrand disease (VWD) to thrombotic conditions [3].

Regarding low VWF, which is defined by mild to moderate reductions in plasma VWF antigen (VWF:Ag) levels (30-50 IU/dL), its pathogenesis remains poorly understood. However, some studies suggest that enhanced VWF clearance may contribute to its pathobiology [4]. Also, the number of rare nonsynonymous variants in the VWF gene significantly predicts VWF:Ag levels [1]. In COVID-19, increased VWF levels, often accompanied by decreased ADAMTS-13 activity, may promote (micro)thrombosis [2]. In acute myocardial infarction patients, higher plasma VWF:Ag levels are associated with long-term major adverse cardiopulmonary and cerebrovascular events (MACEs) [5].

In conclusion, Vwf is essential for maintaining hemostasis. Studies, although not specifically from KO/CKO mouse models in the provided references, have shed light on its role in various disease conditions such as VWD, COVID-19-related thrombosis, and acute myocardial infarction outcomes. Understanding Vwf function contributes to better management and treatment strategies for these diseases.

References:

1. Sadler, Brooke, Christopherson, Pamela A, Haller, Gabe, Montgomery, Robert R, Di Paola, Jorge. . von Willebrand factor antigen levels are associated with burden of rare nonsynonymous variants in the VWF gene. In Blood, 137, 3277-3283. doi:10.1182/blood.2020009999. https://pubmed.ncbi.nlm.nih.gov/33556167/

2. Favaloro, Emmanuel J, Henry, Brandon Michael, Lippi, Giuseppe. 2021. Increased VWF and Decreased ADAMTS-13 in COVID-19: Creating a Milieu for (Micro)Thrombosis. In Seminars in thrombosis and hemostasis, 47, 400-418. doi:10.1055/s-0041-1727282. https://pubmed.ncbi.nlm.nih.gov/33893632/

3. Xiang, Yaozu, Hwa, John. . Regulation of VWF expression, and secretion in health and disease. In Current opinion in hematology, 23, 288-93. doi:10.1097/MOH.0000000000000230. https://pubmed.ncbi.nlm.nih.gov/26771163/

4. Doherty, Dearbhla, Byrne, Mary, Nolan, Margaret, James, Paula D, O'Donnell, James S. . Enhanced VWF clearance in low VWF pathogenesis: limitations of the VWFpp/VWF:Ag ratio and clinical significance. In Blood advances, 7, 302-308. doi:10.1182/bloodadvances.2022007340. https://pubmed.ncbi.nlm.nih.gov/35523118/

5. Xier, Zulipiyemu, Zhu, Yu-Xia, Tang, Shou-Wei, Huojia, Guzailinuer, Peng, Hui. 2023. Plasma VWF: Ag levels predict long-term clinical outcomes in patients with acute myocardial infarction. In Frontiers in cardiovascular medicine, 9, 1013815. doi:10.3389/fcvm.2022.1013815. https://pubmed.ncbi.nlm.nih.gov/36684571/