Mechanical activation of a multimeric adhesive protein through domain conformational change

Von Willebrand factor in diagnostics and treatment of cardiovascular disease: Recent advances and prospects

Von Willebrand factor (VWF) is a large multimeric glycoprotein involved in hemostasis. It is essential for platelet adhesion to the subendothelium of the damaged endothelial layer at high shear rates. Such shear rates occur in small-diameter arteries, especially at stenotic sites. Moreover, VWF carries coagulation factor VIII and protects it from proteolysis in the bloodstream. Deficiency or dysfunction of VWF predisposes to bleeding. In contrast, an increase in the concentration of high molecular weight multimers (HMWM) of VWF is closely associated with arterial thrombotic events. Severe aortic stenosis (AS) or hypertrophic obstructive cardiomyopathy (HOCM) can deplete HMWM of VWF and lead to cryptogenic, gastrointestinal, subcutaneous, and mucosal bleeding. Considering that VWF facilitates primary hemostasis and a local inflammatory response at high shear rates, its dysfunction may contribute to the development of coronary artery disease (CAD) and its complications. However, current diagnostic methods do not allow for an in-depth analysis of this contribution. The development of novel diagnostic techniques, primarily microfluidic, is underway. Such methods can provide physiologically relevant assessments of VWF function at high shear rates; however, they have not been introduced into clinical practice. The development and use of agents targeting VWF interaction with the vessel wall and/or platelets may be reasonable in prevention of CAD and its complications, given the prominent role of VWF in arterial thrombosis.

Hyperadhesive von Willebrand Factor Promotes Extracellular Vesicle-Induced Angiogenesis: Implication for LVAD-Induced Bleeding

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VWF in patients on LVAD supports was hyperadhesive, activated platelets, and generated platelet-derived extracellular vesicles.

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Extracellular vesicles from LVAD patients and those from shear-activated platelets promoted aberrant angiogenesis in a VWF-dependent manner.

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The activated VWF exposed the A1 domain through the synergistic actions of oxidative stress and HSS generated in LVAD-driven circulation.

Bleeding associated with left ventricular assist device (LVAD) implantation has been attributed to the loss of large von Willebrand factor (VWF) multimers to excessive cleavage by ADAMTS-13, but this mechanism is not fully supported by the current evidence. We analyzed VWF reactivity in longitudinal samples from LVAD patients and studied normal VWF and platelets exposed to high shear stress to show that VWF became hyperadhesive in LVAD patients to induce platelet microvesiculation. Platelet microvesicles activated endothelial cells, induced vascular permeability, and promoted angiogenesis in a VWF-dependent manner. Our findings suggest that LVAD-driven high shear stress primarily activates VWF, rather than inducing cleavage in the majority of patients.

Wall Shear Stress Alteration: a Local Risk Factor of Atherosclerosis

PURPOSE OF REVIEW

Wall shear stress describes the mechanical influence of blood flow on the arterial wall. In this review, we discuss the role of the wall shear stress in the development of atherosclerosis and its complications.

RECENT FINDINGS

Areas with chronically low, oscillating wall shear stress are most prone to plaque development and include outer bifurcation walls and inner walls of arches. In some diseases, patients have lower wall shear stress even in straight arterial segments; also, these findings were associated with atherosclerosis. High wall shear stress develops in the distal part (shoulder) of a stenosis and contributes to plaque destabilization. Wall shear stress changes are involved in the development of atherosclerosis. They are not fully understood yet and act in concert with tangential wall stress.

Targeting shear gradient activated von Willebrand factor by the novel single-chain antibody A1 reduces occlusive thrombus formation in vitro

Intraluminal thrombus formation precipitates conditions such as acute myocardial infarction and disturbs local blood flow resulting in areas of rapidly changing blood flow velocities and steep gradients of blood shear rate. Shear rate gradients are known to be pro-thrombotic with an important role for the shear-sensitive plasma protein von Willebrand factor (VWF). Here, we developed a single-chain antibody (scFv) that targets a shear gradient specific conformation of VWF to specifically inhibit platelet adhesion at sites of SRGs but not in areas of constant shear. Microfluidic flow channels with stenotic segments were used to create shear rate gradients during blood perfusion. VWF-GPIbα interactions were increased at sites of shear rate gradients compared to constant shear rate of matched magnitude. The scFv-A1 specifically reduced VWF-GPIbα binding and thrombus formation at sites of SRGs but did not block platelet deposition and aggregation under constant shear rate in upstream sections of the channels. Significantly, the scFv A1 attenuated platelet aggregation only in the later stages of thrombus formation. In the absence of shear, direct binding of scFv-A1 to VWF could not be detected and scFV-A1 did not inhibit ristocetin induced platelet agglutination. We have exploited the pro-aggregatory effects of SRGs on VWF dependent platelet aggregation and developed the shear-gradient sensitive scFv-A1 antibody that inhibits platelet aggregation exclusively at sites of shear rate gradients. The lack of VWF inhibition in non-stenosed vessel segments places scFV-A1 in an entirely new class of anti-platelet therapy for selective blockade of pathological thrombus formation while maintaining normal haemostasis.

Dependence of Membrane Tether Strength on Substrate Rigidity Probed by Single-Cell Force Spectroscopy

Substrate rigidity modulates cell mechanics, which affect cell migration and proliferation. Quantifying the effects of substrate rigidity on cancer cell mechanics requires a quantifiable parameter that can be measured for individual cells, as well as a substrate platform with rigidity being the only variable. Here we used single-cell force spectroscopy to pull cancer cells on substrates varying only in rigidity, and extracted a parameter from the force-distance curves to be used to quantify the properties of membrane tethers. Our results showed that tether force increases with substrate rigidity until it reaches its asymptotic limit. The variations are similar for all three cancer cell lines studied, and the largest change occurs in the rigidity regions of softer tissues, indicating a universal response of cancer cell elasticity to substrate rigidity.

Turbulent Flow Promotes Cleavage of VWF (von Willebrand Factor) by ADAMTS13 (A Disintegrin and Metalloproteinase With a Thrombospondin Type-1 Motif, Member 13)

Objective—

Acquired von Willebrand syndrome is defined by excessive cleavage of the VWF (von Willebrand Factor) and is associated with impaired primary hemostasis and severe bleeding. It often develops when blood is exposed to nonphysiological flow such as in aortic stenosis or mechanical circulatory support. We evaluated the role of laminar, transitional, and turbulent flow on VWF cleavage and the effects on VWF function.

Approach and Results—

We used a vane rheometer to generate laminar, transitional, and turbulent flow and evaluate the effect of each on VWF cleavage in the presence of ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type-1 motif, member 13). We performed functional assays to evaluate the effect of these flows on VWF structure and function. Computational fluid dynamics was used to estimate the flow fields and forces within the vane rheometer under each flow condition. Turbulent flow is required for excessive cleavage of VWF in an ADAMTS13-dependent manner. The assay was repeated with whole blood, and the turbulent flow had the same effect. Our computational fluid dynamics results show that under turbulent conditions, the Kolmogorov scale approaches the size of VWF. Finally, cleavage of VWF in this study has functional consequences under flow as the resulting VWF has decreased ability to bind platelets and collagen.

Conclusions—

Turbulent flow mediates VWF cleavage in the presence of ADAMTS13, decreasing the ability of VWF to sustain platelet adhesion. These findings impact the design of mechanical circulatory support devices and are relevant to pathological environments where turbulence is added to circulation.

Force-Regulated Refolding of the Mechanosensory Domain in the Platelet Glycoprotein Ib-IX Complex

In platelets, the glycoprotein (GP) Ib-IX receptor complex senses blood shear flow and transmits the mechanical signals into platelets. Recently, we have discovered a juxtamembrane mechanosensory domain (MSD) within the GPIbα subunit of GPIb-IX. Mechanical unfolding of the MSD activates GPIb-IX signaling into platelets, leading to their activation and clearance. Using optical tweezer-based single-molecule force measurement, we herein report a systematic biomechanical characterization of the MSD in its native, full-length receptor complex and a recombinant, unglycosylated MSD in isolation. The native MSD unfolds at a resting rate of 9 × 10^-3 s^-1. Upon exposure to pulling forces, MSD unfolding accelerates exponentially over a force scale of 2.0 pN. Importantly, the unfolded MSD can refold with or without applied forces. The unstressed refolding rate of MSD is ∼17 s^-1 and slows exponentially over a force scale of 3.7 pN. Our measurements confirm that the MSD is relatively unstable, with a folding free energy of 7.5 k_BT. Because MSD refolding may turn off GPIb-IX's mechanosensory signals, our results provide a mechanism for the requirement of a continuous pulling force of >15 pN to fully activate GPIb-IX.

Structural and Functional Plasticity of Collagen Fibrils

Collagen is a major component of the subendothelial matrix and participates in bleeding arrest by activating and aggregating platelets at the site of vascular injury. The most common type I collagen exists in both soluble and fibrillar forms, but structural exchangeability between the two forms is currently unknown. Using atomic force microscopy, we show that type I collagen switches between soluble and fibrillar forms in a pH-dependent and ion-independent manner. Fibrillar collagen is rope like with characteristic "D-bands." The collagen fibrils can be disrupted with 0.1 M acetic acid and will reform when the pH is adjusted to 7.4. This structural plasticity leads to drastically different activities, with fibrillar collagen being significantly more active for platelets under static and flow conditions. More important, by probing with noncontact hopping probe ion-conductance microscopy, we find that platelets adherent to fibrillar collagen present primarily as high-density bubble shapes that have undergone rapid microvesiculation.

Correlating Conformational Dynamics with the Von Willebrand Factor Reductase Activity of Factor H Using Single Molecule Force Measurements

Activation of proteins often involves conformational transitions, and these switches are often difficult to characterize in multidomain proteins. Full-length factor H (FH), consisting of 20 small consensus repeat domains (150 kD), is a complement control protein that regulates the activity of the alternative complement pathway. Different preparations of FH can also reduce the disulfide bonds linking large Von Willebrand factor (VWF) multimers into smaller, less adhesive forms. In contrast, commercially available purified FH (pFH) has little or no VWF reductase activity unless the pFH is chemically modified by either ethylenediaminetetraacetic acid (EDTA) or urea. We used atomic force microscopy single molecule force measurements to investigate different forms of FH, including recombinant FH and pFH, in the presence or absence of EDTA and urea, and to correlate the conformational changes to its activities. We found that the FH conformation depends on the method used for sample preparation, which affects the VWF reductase activity of FH.

14-3-3 proteins in platelet biology and glycoprotein Ib-IX signaling

Members of the 14-3-3 family of proteins function as adapters/modulators that recognize phosphoserine/phosphothreonine-based binding motifs in many intracellular proteins and play fundamental roles in signal transduction pathways of eukaryotic cells. In platelets, 14-3-3 plays a wide range of regulatory roles in phosphorylation-dependent signaling pathways, including G-protein signaling, cAMP signaling, agonist-induced phosphatidylserine exposure, and regulation of mitochondrial function. In particular, 14-3-3 interacts with several phosphoserine-dependent binding sites in the major platelet adhesion receptor, the glycoprotein Ib-IX complex (GPIb-IX), regulating its interaction with von Willebrand factor (VWF) and mediating VWF/GPIb-IX-dependent mechanosignal transduction, leading to platelet activation. The interaction of 14-3-3 with GPIb-IX also plays a critical role in enabling the platelet response to low concentrations of thrombin through cooperative signaling mediated by protease-activated receptors and GPIb-IX. The various functions of 14-3-3 in platelets suggest that it is a possible target for the treatment of thrombosis and inflammation.

Cancer cell-derived von Willebrand factor enhanced metastasis of gastric adenocarcinoma

Cancer prognosis is poor for patients with blood-borne metastasis. Platelets are known to assist cancer cells in transmigrating through the endothelium, but ligands for the platelet-mediated cancer metastasis remain poorly defined. von Willebrand factor (vWF) is a major platelet ligand that has been widely used as a biomarker in cancer and associated inflammation. However, its functional role in cancer growth and metastasis is largely unknown. Here we report that gastric cancer cells from patients and cells from two well-established gastric cancer lines express vWF and secrete it into the circulation, upon which it rapidly becomes cell-bound to mediate cancer-cell aggregation and interaction with platelets and endothelial cells. The vWF-mediated homotypic and heterotypic cell-cell interactions promote the pulmonary graft of vWF-overexpressing gastric cancer BGC823 cells in a mouse model. The metastasis-promoting activity of vWF was blocked by antibodies against vWF and its platelet receptor GP Ibα. It was also reduced by an inhibitory siRNA that suppresses vWF expression. These findings demonstrate a causal role of cancer-cell-derived vWF in mediating gastric cancer metastasis and identify vWF as a new therapeutic target.

Thrombosis in diabetes: a shear flow effect?

Cardiovascular events are the major cause of morbidity and mortality in Type 2 diabetes (T2D). This condition is associated with heightened platelet reactivity, contributing to increased atherothrombotic risk. Indeed, individuals with diabetes respond inadequately to standard antiplatelet therapy. Furthermore, they often experience recurrent events as well as side effects that include excess bleeding. This highlights the need for identification of novel regulators of diabetes-associated thrombosis to target for therapeutic intervention. It is well established that platelet aggregation, a process essential for thrombus formation, is tightly regulated by shear stress; however, the mechanisms underlying shear activation of platelets, particularly in the setting of diabetes, are still poorly understood. This review will address the limitations of current diagnostic systems to assess the importance of shear stress in the regulation of thrombus formation in T2D, and the inability to recapitulate the pro-thrombotic phenotype seen clinically in the setting of T2D. Moreover, we will discuss recent findings utilizing new technologies to define the importance of shear stress in thrombus formation and their potential application to the setting of diabetes. Finally, we will discuss the potential of targeting shear-dependent mechanisms of thrombus formation as a novel therapeutic approach in the setting of T2D.

A biophysical view on von Willebrand factor activation

The process of hemostatic plug formation at sites of vascular injury crucially relies on the large multimeric plasma glycoprotein von Willebrand factor (VWF) and its ability to recruit platelets to the damaged vessel wall via interaction of its A1 domain with platelet GPIbα. Under normal blood flow conditions, VWF multimers exhibit a very low binding affinity for platelets. Only when subjected to increased hydrodynamic forces, which primarily occur in connection with vascular injury, VWF can efficiently bind to platelets. This force-regulation of VWF's hemostatic activity is not only highly intriguing from a biophysical perspective, but also of eminent physiological importance. On the one hand, it prevents undesired activity of VWF in intact vessels that could lead to thromboembolic complications and on the other hand, it enables efficient VWF-mediated platelet aggregation exactly where needed. Here, we review recent studies that mainly employed biophysical approaches in order to elucidate the molecular mechanisms underlying the complex mechano-regulation of the VWF-GPIbα interaction. Their results led to two main hypotheses: first, intramolecular shielding of the A1 domain is lifted upon force-induced elongation of VWF; second, force-induced conformational changes of A1 convert it from a low-affinity to a high-affinity state. We critically discuss these hypotheses and aim at bridging the gap between the large-scale behavior of VWF as a linear polymer in hydrodynamic flow and the detailed properties of the A1-GPIbα bond at the single-molecule level.

A physical description of the adhesion and aggregation of platelets

The early stages of clot formation in blood vessels involve platelet adhesion-aggregation. Although these mechanisms have been extensively studied, gaps in their understanding still persist. We have performed detailed in vitro experiments, using the well-known Impact-R device, and developed a numerical model to better describe and understand this phenomenon. Unlike previous studies, we took into account the differential role of pre-activated and non-activated platelets, as well as the three-dimensional nature of the aggregation process. Our investigation reveals that blood albumin is a major parameter limiting platelet aggregate formation in our experiment. Simulations are in very good agreement with observations and provide quantitative estimates of the adhesion and aggregation rates that are hard to measure experimentally. They also provide a value of the effective diffusion of platelets in blood subject to the shear rate produced by the Impact-R.

Mutual A domain interactions in the force sensing protein von Willebrand factor

The von Willebrand factor (VWF) is a glycoprotein in the blood that plays a central role in hemostasis. Among other functions, VWF is responsible for platelet adhesion at sites of injury via its A1 domain. Its adjacent VWF domain A2 exposes a cleavage site under shear to degrade long VWF fibers in order to prevent thrombosis. Recently, it has been shown that VWF A1/A2 interactions inhibit the binding of platelets to VWF domain A1 in a force-dependent manner prior to A2 cleavage. However, whether and how this interaction also takes place in longer VWF fragments as well as the strength of this interaction in the light of typical elongation forces imposed by the shear flow of blood remained elusive. Here, we addressed these questions by using single molecule force spectroscopy (SMFS), Brownian dynamics (BD), and molecular dynamics (MD) simulations. Our SMFS measurements demonstrate that the A2 domain has the ability to bind not only to single A1 domains but also to VWF A1A2 fragments. SMFS experiments of a mutant [A2] domain, containing a disulfide bond which stabilizes the domain against unfolding, enhanced A1 binding. This observation suggests that the mutant adopts a more stable conformation for binding to A1. We found intermolecular A1/A2 interactions to be preferred over intramolecular A1/A2 interactions. Our data are also consistent with the existence of two cooperatively acting binding sites for A2 in the A1 domain. Our SMFS measurements revealed a slip-bond behavior for the A1/A2 interaction and their lifetimes were estimated for forces acting on VWF multimers at physiological shear rates using BD simulations. Complementary fitting of AFM rupture forces in the MD simulation range adequately reproduced the force response of the A1/A2 complex spanning a wide range of loading rates. In conclusion, we here characterized the auto-inhibitory mechanism of the intramolecular A1/A2 bond as a shear dependent safeguard of VWF, which prevents the interaction of VWF with platelets.

Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces.

Acquired von Willebrand syndrome associated with left ventricular assist device

Left ventricular assist devices (LVAD) provide cardiac support for patients with end-stage heart disease as either bridge or destination therapy, and have significantly improved the survival of these patients. Whereas earlier models were designed to mimic the human heart by producing a pulsatile flow in parallel with the patient's heart, newer devices, which are smaller and more durable, provide continuous blood flow along an axial path using an internal rotor in the blood. However, device-related hemostatic complications remain common and have negatively affected patients' recovery and quality of life. In most patients, the von Willebrand factor (VWF) rapidly loses large multimers and binds poorly to platelets and subendothelial collagen upon LVAD implantation, leading to the term acquired von Willebrand syndrome (AVWS). These changes in VWF structure and adhesive activity recover quickly upon LVAD explantation and are not observed in patients with heart transplant. The VWF defects are believed to be caused by excessive cleavage of large VWF multimers by the metalloprotease ADAMTS-13 in an LVAD-driven circulation. However, evidence that this mechanism could be the primary cause for the loss of large VWF multimers and LVAD-associated bleeding remains circumstantial. This review discusses changes in VWF reactivity found in patients on LVAD support. It specifically focuses on impacts of LVAD-related mechanical stress on VWF structural stability and adhesive reactivity in exploring multiple causes of AVWS and LVAD-associated hemostatic complications.

Single-molecule force measurements of the polymerizing dimeric subunit of von Willebrand factor

Von Willebrand factor (VWF) multimers are large adhesive proteins that are essential to the initiation of hemostatic plugs at sites of vascular injury. The binding of VWF multimers to platelets, as well as VWF proteolysis, is regulated by shear stresses that alter VWF multimeric conformation. We used single molecule manipulation with atomic force microscopy (AFM) to investigate the effect of high fluid shear stress on soluble dimeric and multimeric forms of VWF. VWF dimers are the smallest unit that polymerizes to construct large VWF multimers. The resistance to mechanical unfolding with or without exposure to shear stress was used to evaluate VWF conformational forms. Our data indicate that, unlike recombinant VWF multimers (RVWF), recombinant dimeric VWF (RDVWF) unfolding force is not altered by high shear stress (100dynes/cm^{2} for 3 min at 37^{∘}C). We conclude that under the shear conditions used (100dynes/cm^{2} for 3 min at 37^{∘}C), VWF dimers do not self-associate into a conformation analogous to that attained by sheared large VWF multimers.

Single molecule force measurements of perlecan/HSPG2: A key component of the osteocyte pericellular matrix

Perlecan/HSPG2, a large, monomeric heparan sulfate proteoglycan (HSPG), is a key component of the lacunar canalicular system (LCS) of cortical bone, where it is part of the mechanosensing pericellular matrix (PCM) surrounding the osteocytic processes and serves as a tethering element that connects the osteocyte cell body to the bone matrix. Within the pericellular space surrounding the osteocyte cell body, perlecan can experience physiological fluid flow drag force and in that capacity function as a sensor to relay external stimuli to the osteocyte cell membrane. We previously showed that a reduction in perlecan secretion alters the PCM fiber composition and interferes with bone's response to a mechanical loading in vivo. To test our hypothesis that perlecan core protein can sustain tensile forces without unfolding under physiological loading conditions, atomic force microscopy (AFM) was used to capture images of perlecan monomers at nanoscale resolution and to perform single molecule force measurement (SMFMs). We found that the core protein of purified full-length human perlecan is of suitable size to span the pericellular space of the LCS, with a measured end-to-end length of 170±20 nm and a diameter of 2-4 nm. Force pulling revealed a strong protein core that can withstand over 100 pN of tension well over the drag forces that are estimated to be exerted on the individual osteocyte tethers. Data fitting with an extensible worm-like chain model showed that the perlecan protein core has a mean elastic constant of 890 pN and a corresponding Young's modulus of 71 MPa. We conclude that perlecan has physical properties that would allow it to act as a strong but elastic tether in the LCS.

DNA under Force: Mechanics, Electrostatics, and Hydration

Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology.

Update on von Willebrand factor multimers: focus on high-molecular-weight multimers and their role in hemostasis

Normal hemostasis requires von Willebrand factor (VWF) to support platelet adhesion and aggregation at sites of vascular injury. VWF is a multimeric glycoprotein built from identical subunits that contain binding sites for both platelet glycoprotein receptors and collagen. The adhesive activity of VWF depends on the size of its multimers, which range from 500 to over 10 000 kDa. There is good evidence that the high-molecular-weight multimers (HMWM), which are 5000-10 000 kDa, are the most effective in supporting interaction with collagen and platelet receptors and in facilitating wound healing under conditions of shear stress. Thus, these HMWM of VWF are of particular clinical interest. The unusually large multimers of VWF are, under normal conditions, cleaved by the plasma metalloproteinase ADAMTS13 to smaller, less adhesive multimers. A reduction or lack of HMWM, owing to a multimerization defect of VWF or to an increased susceptibility of VWF for ADAMTS13, leads to a functionally impaired VWF and the particular type 2A of von Willebrand disease. This review considers the biology and function of VWF multimers with a particular focus on the characterization of HMWM - their production, storage, release, degradation, and role in normal physiology. Evidence from basic research and the study of clinical diseases and their management highlight a pivotal role for the HMWM of VWF in hemostasis.

The various states of von Willebrand factor and their function in physiology and pathophysiology

The specific interactions of von Willebrand factor (VWF) with the vessel wall, platelets or other interfaces strongly depend on (a shear-induced) VWF activation. Shear flow has been shown to induce a conformational transition of VWF, but is modulated by its thermodynamic state (state-function relationship). The state in turn is determined by physical (e.g. vessel geometry), physico-chemical (e.g. pH) and molecular-biological (e.g. mutants, binding) factors. Combining established results with recent insights, we reconstruct VWF biology and its state-function relationship from endothelial cell release to final degradation in the human vasculature. After VWF secretion, endothelial-anchored and shear activated VWF multimers can rapidly interact with surrounding colloids, typically with platelets. Simultaneously, this VWF activation enables ADAMTS13 to cleave VWF multimers thereby limiting VWF binding capacity. The subsequent cell-surface dissociation leads to a VWF recoiling to a globular conformation, shielding from further degradation by ADAMTS13. High local concentrations of these soluble VWF multimers, transported to the downstream vasculature, are capable for an immediate reactivation and re-polymerisation initiating colloid-binding or VWF-colloid aggregation at the site of inflamed endothelium, vessel injuries or pathological high-shear areas. Focusing on these functional steps in the lifecycle of VWF, its qualitative and quantitative deficiencies in the different VWD types will facilitate more precise diagnostics and reliable risk stratification for prophylactic therapies. The underlying biophysical principles are of general character, which broadens prospective studies on the physiological and pathophysiological impact of VWF and VWF-associated diseases and beares hope for a more universal understanding of an entire class of phenomena.