In this video lecture, Dr. Cécile Denis discusses:
- How naturally occurring and genetically engineered animal models have advanced understanding of von Willebrand disease and von Willebrand factor biology.
- Insights gained from mouse models into the role of von Willebrand factor in hemostasis, thrombosis, stroke, vascular remodeling, and tumor biology.
- How humanized animal models are helping investigators study disease mechanisms and evaluate novel therapies for von Willebrand disease.
Cécile V. Denis, PhD, is Director of Research at INSERM (Institut National de la Santé et de la Recherche Médicale) and the Director of Unit 1176 (Hemostasis-Inflammation-Thrombosis) at the Kremlin-Bicêtre Hospital. After completing her PhD in Biological Sciences at the University of Paris 7 in 1993, she spent seven years conducting postdoctoral research at Harvard Medical School. Upon returning to France, she established her own academic team via INSERM’s prestigious Avenir program.
Dr. Denis has dedicated over 30 years to investigating bleeding and vascular disorders. Her pioneering work focuses heavily on the molecular mechanisms of von Willebrand factor biology, the development of specialized murine models and original treatments for von Willebrand disease. An internationally recognized expert in thrombosis and hemostasis, she has published over 180 peer-reviewed articles and holds 11 patents. In recognition of her contributions to medical science, Dr. Denis was awarded the French Légion d’Honneur (2012), the International Society of Thrombosis and Haemostasis (ISTH) BACH Award (2017), and the Prix Jean-Paul Binet from the Foundation for Medical Research (2025).
(Video Lecture Summary)
Introduction
Dr. Cécile Denis reviews the animal models that have shaped our understanding of von Willebrand disease (VWD) and the broader biological functions of von Willebrand factor (VWF). She explains how naturally occurring animal models, genetically engineered mice, and more recently developed humanized models have provided unique insights into disease mechanisms that would be difficult or impossible to obtain in human studies alone. These models have expanded our understanding of both the hemostatic and non-hemostatic roles of VWF while providing valuable platforms for therapeutic development.
Naturally Occurring and Engineered Animal Models
Dr. Denis begins by noting that several animal species naturally develop VWD, including pigs, dogs, rabbits, cats, horses, and cattle. Although pigs and dogs have historically been important research models, their use is limited by high costs, challenges maintaining colonies, and genetic variability because these animals are generally not inbred.
For these reasons, mice have become the preferred experimental model. She describes both naturally occurring inbred mouse strains with altered VWF levels and genetically engineered models designed to reproduce specific forms of VWD. These include VWF-deficient mice, knock-in models carrying disease-causing mutations, and semi- or fully humanized mouse models that more closely mimic human VWF biology.
VWF-Deficient Mice Reveal the Role of VWF in Hemostasis
The first genetically engineered VWF-deficient mice, developed in 1998, completely lack VWF in plasma, platelets, and endothelial cells. As expected, these mice exhibit a severe bleeding phenotype, readily demonstrated by tail bleeding assays.
These knockout models have become indispensable tools for investigating the role of VWF in hemostasis and thrombosis. Using experimental thrombosis models, investigators demonstrated that platelet adhesion is markedly delayed in the absence of VWF and that stable occlusive thrombi fail to develop following vascular injury. Restoration of mutant forms of VWF further established the complementary importance of both the GPIbα and αIIbβ3 platelet-binding interactions during thrombus formation.
Beyond Hemostasis: VWF in Tumor Biology
One of the unexpected discoveries arising from VWF-deficient mice concerns the role of VWF in cancer metastasis.
Based on the observation that tumor cells express receptors capable of binding VWF, investigators initially hypothesized that VWF might facilitate metastatic spread. Instead, experimental studies produced the opposite result. Mice lacking VWF developed significantly more metastatic lesions following injection of melanoma cells than wild-type animals.
Subsequent experiments demonstrated that VWF promotes apoptosis of tumor cells, suggesting that VWF exerts a protective effect against metastasis rather than enhancing it. Dr. Denis notes that some tumors have evolved mechanisms to evade this VWF-mediated apoptosis, illustrating the complex relationship between VWF and cancer biology.
VWF and Vascular Remodeling
Dr. Denis next discusses the role of VWF in vascular biology, focusing on intimal hyperplasia.
Although VWF is well known for its presence beneath the endothelial surface, studies have also identified VWF deeper within diseased vessel walls, particularly in regions containing proliferating vascular smooth muscle cells. Using carotid artery ligation models, investigators demonstrated that vascular remodeling and neointimal formation are markedly reduced in VWF-deficient mice.
Further mechanistic studies identified interactions between the VWF A2 domain, low-density lipoprotein receptor-related protein 4 (LRP4), and integrin αVβ3 that promote smooth muscle cell proliferation. These findings illustrate how VWF contributes to vascular remodeling independently of its traditional hemostatic functions.
VWF in Thrombosis and Stroke
Animal models have also clarified the importance of VWF in arterial thrombosis and ischemic stroke.
In experimental stroke models produced by middle cerebral artery occlusion, VWF-deficient mice develop substantially smaller areas of cerebral ischemia than wild-type animals. This protection is accompanied by reduced thrombus formation and decreased inflammatory cell infiltration within injured brain tissue.
These observations suggest that targeting VWF may represent a therapeutic strategy for ischemic stroke by simultaneously limiting thrombosis and inflammation.
Animal Models for Therapeutic Development
Dr. Denis reviews how VWF-deficient mice have also been used to evaluate novel therapeutic approaches.
She describes studies using synthetic nanoparticles coated with platelet-mimetic peptides. In vitro, these nanoparticles improved platelet adhesion and thrombus formation in VWF-deficient blood. In vivo, administration of the particles significantly reduced blood loss during tail bleeding assays, illustrating how animal models can accelerate development of innovative therapies for bleeding disorders.
Knock-In Models of Specific VWD Subtypes
Beyond complete VWF deficiency, investigators have generated numerous knock-in mouse models carrying mutations responsible for individual VWD subtypes.
Dr. Denis focuses on type 2B VWD, a gain-of-function disorder characterized by spontaneous binding of VWF to platelets. Despite enhanced platelet binding, affected patients experience increased bleeding, thrombocytopenia, giant platelets, and loss of high-molecular-weight multimers.
The corresponding mouse model faithfully reproduces these clinical features. Using these animals, investigators demonstrated that abnormal VWF-platelet interactions impair platelet signaling, reduce RAP1 activation, disrupt megakaryocyte cytoskeletal organization, and ultimately impair platelet production. These studies clarified the mechanisms responsible for thrombocytopenia and giant platelet formation in type 2B VWD.
Humanized Mouse Models
One limitation of traditional mouse models is the species incompatibility between human VWF and murine platelet GPIbα, preventing accurate evaluation of human VWF therapies.
To overcome this challenge, researchers have developed chimeric and fully humanized mouse models expressing human VWF and human platelet GPIbα. Dr. Denis describes a recently developed fully humanized model that unexpectedly exhibited reduced VWF expression while maintaining normal VWF activity, effectively creating a model of type 1 VWD.
Although unanticipated, this phenotype has proven advantageous because it allows investigators to evaluate therapies designed specifically for patients with type 1 disease. She presents studies demonstrating correction of the bleeding phenotype following treatment with recombinant human VWF or histamine-induced release of endogenous VWF.
Conclusion
Dr. Denis concludes that animal models have been indispensable for advancing knowledge of von Willebrand disease and von Willebrand factor biology. They have revealed critical roles for VWF in hemostasis, thrombosis, stroke, vascular remodeling, and cancer while providing powerful systems for studying individual VWD subtypes and evaluating emerging therapies. The continued development of humanized models promises to further improve translational research and accelerate the development of novel treatments for patients with VWD.