Plasma Von Willebrand Factor Research Articles

Von Willebrand factor polymorphism (rs1063856) as a risk factor for portal vein thrombosis in chronic liver diseases

BackgroundDue to its well-established involvement in clot formation, von Willebrand factor (vWF) has been held responsible for decades as a risk factor for arterio-venous thrombosis. It is currently unclear how genetic differences in vWF genes relate to the incidence of portal vein thrombosis (PVT). Thus, the aim of this study was to evaluate the significance of vWF:Ag level and vWF gene polymorphism (rs1063856) as risk factors for PVT in patients with chronic liver disease (CLD).Subjects and methodsThis research of 70 individuals with CLD comprised 30 without PVT and 40 with PVT. Twenty patients with PVT-linked hepatocellular carcinoma (HCC) and 20 patients with non-HCC-PVT comprised the two subgroups from the 40 PVT patients. Additionally, 30 healthy volunteers of the same age and gender as the patients were included in the study as a control group. Tests for liver and renal function, coagulation profile, complete blood count, hepatitis virus markers, and vWF:Ag level were conducted. The identification of the vWF gene polymorphism (rs1063856) was assessed using real-time PCR.ResultsWhen comparing CLD patients with PVT to those without PVT and the healthy control group, there was a substantial rise in the vWF: Ag level. Additionally, compared to instances of benign PVT, the vWF:Ag levels were considerably greater in malignant PVT.CLD patients with PVT had higher frequencies of the vWF (rs1063856) AA genotype and A alleles (37.5% and 61.3%, respectively) than did control and non-PVT cases. Patients with the AA genotype showed the highest serum levels of vWF antigen, followed by those with the TA genotype.ConclusionvWF (rs1063856) AA gene polymorphism has a strong correlation with vWF plasma level and may be a risk factor for PVT development in CLD patients. These findings should be included in the risk assessment model to determine and guide management for those patients.

Amelioration of a von Willebrand disease type 2B phenotype invivo upon treatment with allele-selective siRNAs.

Treatment options for the bleeding disorder von Willebrand disease type 2B (VWD2B) are insufficient and fail to address the negative effects of circulating mutant von Willebrand factor (VWF). The dominant-negative nature of VWD2B makes functionally defective VWF an interesting therapeutic target. Previous invitro studies have demonstrated the feasibility of allele-selective silencing of mutant VWF using small interfering RNAs (siRNAs) targeting common single nucleotide polymorphisms (SNPs) in the human VWF gene, an approach that can be applied irrespective of the disease-causing VWF mutation. This study aims to extend this concept to a heterozygous VWD2B mouse model (c.3946G>A; p.Val1316Met) here using mouse strain-specific genetic differences as proxy for human SNPs. Homozygous VWD2B C57BL/6J (2B-B6) mice were crossed with homozygous wild-type 129S1/SvImJ (129S) mice to create heterozygous 2B-B6.129S F1 offspring. These 2B-B6.129S mice were intravenously injected with endothelial-specific lipid nanoparticles loaded with the allele-selective siVwf.B6 or control and 96 hours later, lung Vwf messenger RNA, plasma VWF levels, and phenotypic characteristics were evaluated. Treatment with siVwf.B6 reduced total VWF levels by 50%, with an expected selective reduction in mutant VWF protein. This coincided with normalization of multimeric structure, improved VWF collagen binding/VWF antigen ratio, and normalized bleeding times in two-thirds of heterozygous 2B-B6.129S mice. Being a novel approach in the field of hemostasis, we proved, for VWD, in mice, the concept of selectively inhibiting a mutant dominant-negative allele with siRNAs targeting a single nucleotide variation rather than the disease-causing mutation. For dominant-negative VWD, this offers potential for a customized therapeutic strategy.

Interplay between circulating von Willebrand factor and neutrophils: implications for inflammation, neutrophil function, and von Willebrand factor clearance.

Von Willebrand factor (VWF) plays a critical role in hemostasis, and emerging evidence suggests its involvement in inflammation. Our study aimed to investigate the interaction between circulating plasma VWF and neutrophils (polymorphonuclear cells, PMNs), elucidate the fate of VWF after binding, and explore its impact on neutrophil behavior. Neutrophils were isolated from the whole blood of healthy volunteers, and their interaction with plasma VWF was examined ex vivo. Immunofluorescence imaging revealed an enhanced binding of VWF to neutrophils following stimulation with inflammatory agents (PMA, TNFα, and IL-8) and exposure to shear forces, highlighting a previously unknown interaction. Furthermore, immunofluorescence images demonstrated increased co-localization of VWF with the early endosome marker EEA1 and the late endosome marker Rab7 over time, indicating the uptake of VWF by neutrophils subsequent to the binding. This was supported by a significant decrease in VWF antigen levels in the supernatant of cells after stimulation. Moreover, stimulated neutrophils exposed to purified plasma-derived VWF exhibited elevated expression of neutrophil surface markers CD45 and CD66b, indicative of altered neutrophil function related to cell adhesion, migration, and phagocytosis. These findings suggest that VWF binding can modulate neutrophil function, potentially influencing their role in immune responses and inflammation. In summary, our study provides novel insights into the complex interplay between VWF and neutrophils, shedding light on the multifaceted roles of VWF in inflammation. Importantly, we have identified neutrophils as potential cellular mediators involved in the clearance of VWF from circulation, introducing a novel mechanism for VWF removal.

A mutant complement factor H (W1183R) enhances proteolytic cleavage of von Willebrand factor by ADAMTS-13 under shear.

A loss-of-functional mutation (W1183R) in human complement factor H (CFH) is associated with complement-associated hemolytic uremic syndrome; mice carrying a similar mutation (W1206R) in CFH also develop thrombotic microangiopathy but its plasma von Willebrand factor (VWF) multimer sizes were dramatically reduced. The mechanism underlying such a dramatic change in plasma VWF multimer distribution in these mice is not fully understood. To determine the VWF and CFH interaction and how CFH proteins affect VWF multimer distribution. We employed recombinant protein expression, purification, and various biochemical and biophysical tools. Purified recombinant W1183R-CFH but not wild-type (WT) CFH protein enhanced the proteolytic cleavage of both peptidyl and multimeric VWF substrates by recombinant ADAMTS-13 in a concentration-dependent manner. Microscale thermophoresis assay demonstrated that both W1183R-CFH and WT-CFH proteins bound various VWF fragments (eg, AIM-A1, A1-A2-A3, D'D3, D'D3-A1, and D'D3-A1-A2) with high affinities. Optical tweezer experiments further showed a concentration-dependent alteration in the contour length (Lc) and the persistent length (Lp) following pulling VWF-A2 domain in the presence of W1183R-CFH or WT-CFH protein. AlphaFold experiments revealed conformational changes in the VWF-A2, particularly the central region where the cleavage bond resides following addition of W1183R-CFH or WT-CFH protein. These results demonstrate for the first time that W1183R-CFH but not WT-CFH protein enhances the proteolytic cleavage of VWF by ADAMTS-13 under shear. This may be achieved by mechanic-induced conformational changes of the central A2 domain, leading to an enhanced cleavage of Tyr1605-Met1606 bond by ADAMTS-13 under pathophysiological conditions.

Misleading antigenic von Willebrand factor levels in acquired von Willebrand syndrome secondary to monoclonal gammopathy of undetermined significance.

In the diagnosis and treatment of acquired von Willebrand syndrome (AVWS), von Willebrand factor (VWF) antigen levels (VWF:Ag) are helpful for quantifying blood VWF-protein levels. Most clinical laboratories measure VWF:Ag by latex immunoassay (LIA), but underlying diseases of AVWS may influence LIA results. A 60year-old AVWS patient with immunoglobulin G (IgG) kappa-type monoclonal gammopathy of undetermined significance (MGUS) showed reduced VWF activity but normal levels of VWF:Ag. His VWF multimers were broadly decreased, which represented a large discrepancy with VWF:Ag. To investigate the mechanism of this discrepancy, we measured the patient's plasma VWF:Ag by in-house enzyme-linked immunosorbent assay (ELISA) and LIA. We also purified the IgG fraction from the patient's serum and measured VWF:Ag in VWF-deficient plasma supplemented with this fraction. VWF:Ag measured by in-house ELISA (VWF:AgELISA) was much lower than that measured by LIA (VWF:AgLIA), which indicated reduced VWF-protein volume in blood. Indeed, VWF:Ag was detected by LIA in VWF-deficient plasma spiked with a patient-derived IgG fraction. These results suggest that LIA detected a non-specific immunoreaction and overestimated the patient's VWF:AgLIA. Clinicians should be aware that underlying diseases of AVWS could influence the LIA system, and interpret VWF:Ag cautiously.

Laboratory Testing for ADAMTS13 for Thrombotic Thrombocytopenia Purpura and Beyond.

ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), also called von Willebrand factor (VWF) cleaving protease, acts as a moderator of VWF activity. ADAMTS13 cleaves VWF multimers, thereby reducing VWF activity in blood. When ADAMTS13 is absent (e.g., in patients with TTP [thrombotic thrombocytopenia purpura]), accumulation of VWF in plasma can occur, particularly as "ultra-large" VWF multimers, with this leading to adverse outcomes such as thrombosis. Relative ADAMTS13 deficiencies also occur in several other conditions, including secondary thrombotic microangiopathies (TMA), cancer, and with severe infections such as in COVID-19 (coronavirus disease 2019). These situations might therefore be accompanied with relative loss of ADAMTS13, thereby potentially also leading to pathological VWF accumulation, with this then generating a prothrombotic milieu, thus contributing to enhance the risk of thrombosis. Laboratory testing for ADAMTS13 can aid in the diagnosis of such disorders (i.e., TTP, TMA), and help guide their management, with testing now accomplished using various assays. As most presentations of TTP reflect an acquired condition due to anti-ADAMTS13 antibodies, there may also be a need to test for these, as this will also influence clinical management. We herein provide an overview of TTP, note other conditions in which low levels of ADAMTS13 may be present, and then detail laboratory testing for both ADAMTS13 and associated inhibitors.

Clinical Utility of Recently FDA Approved IntelliSep test (Sepsis biomarker) for early Diagnosis of Sepsis: Comparison with other Biomarkers and von Willebrand Factor/ADAMTS13 Ration

Abstract Background Sepsis, a relatively common presentation in emergency departments, is a life-threatening disease. Recently, IntelliSep test by Cytovale (San Francisco, CA) received FDA approval as sepsis biomarker. We investigated clinical utility of this test using 44 patients (19 disease group and 25 non-disease group). Materials and Methods IntelliSep assesses cellular host response via deformability cytometry of leukocyte biophysical properties and intended for use in conjunction with clinical assessments and laboratory findings for early detection of sepsis. Test results are available within 10 minutes. Results consists of IntelliSep Band 1 (low risk, score: 0.1-4.9) to Band 3 (high risk, score: 6.3-10; total scale: 0.1-10). We measured IntelliSep score in 44 patients using EDTA blood. Left over plasma was used for measuring both plasma von Willebrand factor (vWF) antigen and ADAMTS13 antigen by ELISA assays. Monocyte distribution width (MDW) were obtained during routine CBC analysis using Beckman hematology analyzer. Lactate and high sensitivity troponin I were measured using Beckman analyzer. Results The median IntelliSep score was two-fold higher in the disease group (mean score 7.1, SD: 1.5, median: 7.4) compared to non-disease group (mean score 4.0, SD: 1.4, Median: 3.7) indicating that this new test can identify patients with high risk of developing sepsis and also rule out low risk patients (p<0.01 by both Mann-Whitney U test two tailed and t-test two tailed). The median MDW was also 34.8 % higher in the disease group (mean:25.6, SD: 5.0, Median: 24.4) compared to non-disease group (mean: 18.9, SD: 2.4, Median: 18.1) and difference was also statistically significant (p < 0.01 by both Mann-Whitney U test and t-test, two tailed). However, correlation between IntelliSep scores and MDW was only modest (overall, r= 0.66). Both lactate and procalcitonin concentrations were significantly higher in the disease group compared to the non-disease group. Interestingly, high-sensitivity troponin I concentrations were also significantly higher in the disease group. In addition, we observed significantly higher plasma vWF antigen in the disease group compared to the non-disease group (mean: 67.4 ug/mL in disease group vs 34.1 ug/mL in the non-disease group. However, in some patients in the disease group plasma vWF values were 6.8-fold higher than normal. In addition, vWF/ADAMTS13 ratio was also significantly elevated in the disease group compared to non-disease group. Discussion New IntelliSep test is useful in early prediction of sepsis in patients admitted to emergency department and may be superior to MDW and lactate for early diagnosis. Significant increase in plasma vWF in these patients indicate that vWF may also be a surrogate marker for endotheliopathy in sepsis. Lack of correlation between plasma VWF and Intellisep results indicates that these two markers probably measure different pathways for sepsis (endothelial activation vs neutrophil activation).

Increased Platelet Adhesiveness in Patients with Venous Thromboembolic Disease.

Background Association between global platelet function and the risk of venous thromboembolic disease (VTE) has been proposed, though the mechanisms do not involve increased platelet aggregation. However, platelet adhesiveness has not been systematically explored in VTE patients. Objectives To evaluate platelet adhesive functions in VTE patients. Methods Platelet adhesion was evaluated by using whole blood samples from VTE patients, selected based on short closure times on the PFA-100 ( n = 54), and matched healthy individuals ( n = 57) in: (i) the PFA-100, (ii) a cone plate analyzer (CPA), on a plastic surface, (iii) microfluidic devices, with two- and three-dimensional evaluation, and (iv) membrane glycoprotein analysis. Intraplatelet signaling was evaluated in isolated collagen type I (Col-I) activated platelets and platelets adhered on Col-I or von Willebrand factor (VWF) coated coverslips under flow. VWF antigen and ADAMTS-13 activity were measured in plasma samples. Results PFA-100 closure times remained significantly shorter in patients. The CPA test showed a significant increase in the platelet aggregates size when using blood from VTE patients. Platelet adhesion on Col-I revealed a higher area covered by platelets and increased aggregate volume when exposed to samples from VTE patients. Protein P-ZAP70/SYK72 showed a phosphorylation level significantly increased in patients' platelets. Plasma VWF was significantly elevated in VTE patients. Conclusions Platelets from VTE patients exhibit a proadhesive phenotype under flow conditions potentially related to the shortened occlusion times with the PFA-100. This enhanced adhesiveness may be explained by higher intraplatelet ZAP70/SYK72 phosphorylation and increased plasma VWF in patients. Therefore, primary hemostasis plays a significant role in the pathophysiology of VTE.

Conformation-specific RNA aptamers for phenotypic distinction between normal von Willebrand factor and type 2B von Willebrand disease

Abstract The A1 domain in Von Willebrand Factor (VWF) initiates coagulation through binding to platelet glycoprotein GPIbα receptors. Von Willebrand Disease (VWD)-Mutations in A1 that either impair (type 2M) or enhance (type 2B) platelet adhesion to VWF can locally destabilize and even misfold the domain. We leveraged misfolding in the gain-of-function type 2B VWD phenotype as a target, distinct from the normal conformation. Two nuclease-resistant 2′-fluoropyrimidine RNA aptamers were selected to discriminate normal A1 domains from a type 2B V1314D A1 variant in a glycosylated A1A2A3 tri-domain VWF-fragment. Two aptamers, W9 and V1, were isolated that selectively recognize, bind, and inhibit the A1–GPIbα interaction with WT A1A2A3 and V1314D A1A2A3, respectively. These aptamers were tested against their respective recombinant targets, plasma VWF, VWF concentrates, and patient plasma with the heterozygous type 2B VWD R1306W variant using clinical assays, surface plasmon resonance and inhibition assays of platelet adhesion to recombinant A1 and A1A2A3 domains under shear stress. The specificity of W9 and V1 aptamers confirms that pathological conformations of VWD Type 2B proteins are different from normal VWF. The availability of aptamers that distinguish normal plasma-derived VWF from VWD suggests potential applicability in clinical diagnosis of severe gain-of-function phenotypes.

Unfolded von Willebrand factor binds protein S and reduces anticoagulant activity

Unfolded von Willebrand factor binds protein S and reduces anticoagulant activity

Evaluation of a semi-automated test for quantification of von Willebrand multimers

The assessment of von Willebrand factor (VWF) multimer distribution, particularly following the implantation of circulatory support devices, is a crucial parameter in hemostasis. Our study aimed to evaluate the semi-automated quantification of VWF multimers using the Sebia Hydrasys analyzer. Our analysis focused on quantifying high molecular weight, intermediate weight, and low molecular weight VWF multimers. Electrophoretic migration was performed using the Hydrasys 2 scan, and interpretation was carried out using densitometric analysis with the Phoresis software. The Hydrasys scan 2 successfully separated all the expected VWF multimer profiles based on the type of von Willebrand disease. The analysis revealed that in patients with circulatory support devices, elevated levels of plasma VWF rendered multimer migration unanalyzable using the methodology recommended by the manufacturer. Therefore, adjustment to a 100% VWF antigenic level improved gel precision. We also suggest using as a standardized control the Cryocheck™ plasma, and have established reference values. Overall, this semi-automated, standardized, and optimized VWF multimer analysis system allows for an effective assessment of the VWF multimeric profile.

Higher Prevalence of Hepatitis B and C Infections among Indian Patients with Von Willebrand Disease

Background: The use of recombinant coagulation factors has reduced the incidence of hepatitis B and C infections in hemophilia patients. As recombinant von Willebrand factor is not easily available, patients with von Willebrand disease (VWD) may be at higher risk for acquiring hepatitis B and C infections. The prevalence of hepatitis B and C infections in the Indian population is ~0.95% and ~0.3%, respectively. Aims: This single tertiary center study aimed to assess the prevalence of hepatitis B and C infections and the profile of liver disease caused by these viruses among patients with VWD. Methodology: We retrospectively enrolled VWD patients treated in our center from January 2012 to December 2022 and analyzed the prevalence of hepatitis B and C infection and stage of liver disease. Results: Among 189 patients with VWD during the study period, 5 of 61 (8.1%) VWD patients screened were hepatitis B surface antigen positive (age: 34 [24–42] years; median (range); plasma VWF antigen: 10.1, [0–40] IU/dL). One patient had cholangiohepatoma at presentation, whereas none had chronic liver disease. Four of five patients received multiple bloodproduct transfusions before coming to our institution, with 10 (7–18) years interval between 1st transfusion and to detection of hepatitis B infection. Four of the 47 VWD patients (8.5%) screened were positive for hepatitis C virus antibody (48 [43–59] years, plasma VWF antigen: 20 [0–21.5] IU/dL). One patient had chronic liver disease. All four patients received multiple blood product transfusions before coming to our institution, with 15.5 (2–39) years interval between 1st transfusion and to the detection of hepatitis C infection. Conclusions: The prevalence of hepatitis B infection (8.1%) and hepatitis C infection (8.5%) was 8-fold and 28-fold higher, respectively, in VWD patients than the general population in India. VWD patients remain at high risk for acquiring transfusion-transmitted viral infections and appropriate interventions are needed to address this.

Von Willebrand Factor Antigen, Biomarkers of Inflammation, and Microvascular Flap Thrombosis in Reconstructive Surgery.

Background: Microvascular flap surgery has become a routine option for defect correction. The role of von Willebrand factor antigen (VWF:Ag) in the pathophysiology of flap complications is not fully understood. We aim to investigate the predictive value of VWF:Ag for microvascular flap complications and explore the relationship between chronic inflammation and VWF:Ag. Methods: This prospective cohort study included 88 adult patients undergoing elective microvascular flap surgery. Preoperative blood draws were collected on the day of surgery before initiation of crystalloids. The plasma concentration of VWF:Ag as well as albumin, neutrophil-to-lymphocyte ratio (NLR), interleukin-6, and fibrinogen were determined. Results: The overall complication rate was 27.3%, and true flap loss occurred in 11.4%. VWF:Ag levels were higher in true flap loss when compared to patients without complications (217.94 IU/dL [137.27-298.45] vs. 114.14 [95.67-132.71], p = 0.001). Regression analysis revealed the association between VWF:Ag and true flap loss at the cutoff of 163.73 IU/dL (OR 70.22 [10.74-485.28], p = 0.043). Increased VWF:Ag concentrations were linked to increases in plasma fibrinogen (p < 0.001), C-reactive protein (p < 0.001), interleukin-6 (p = 0.032), and NLR (p = 0.019). Conclusions: Preoperative plasma VWF:Ag concentration is linked to biomarkers of inflammation and may be valuable in predicting complications in microvascular flap surgery.

Predictive indicators in peripheral blood and left atrium blood for left atrial spontaneous echo contrast in atrial fibrillation patients

ObjectivesThe purpose of this study was to demonstrate the discriminating predictive indicators in peripheral blood and left atrium blood for predicting the risk of left atrial spontaneous echo contrast (LASEC) in atrial fibrillation patients underwent catheter ablation.MethodsA total of 108 consecutive AF patients treated with radiofrequency ablation between July 2022 and July 2023 were enrolled and divided into two groups based on preprocedural transesophageal echocardiography: the non LASEC group (n = 71) and the LASEC group (n = 37). Circulating platelet and endothelial- derived MPs (PMPs and EMPs) in peripheral blood and left atrial blood were detected. Plasma soluble P-selectin (sP-selectin) and von Willebrand factor (vWF) were observed. Diagnostic efficiency was measured using receiver operating characteristic (ROC) curve.ResultsPeripheral sP-selectin, vWF and EMPs expressions elevated in all subjects when compared to those in left atrium blood. Levels of sP-selectin and vWF were significantly higher in peripheral blood of LASEC group than those of non LASEC group (p = 0.0018,p = 0.0271). Significant accumulations of peripheral PMPs and EMPs were documented in LASEC group by comparison with non LASEC group (p = 0.0395,p = 0.018). The area under curve(AUC) of combined PMPs and sP-selectin in predicting LASEC was 0.769 (95%CI: 0.678–0.845, sensitivity: 86.49%, specificity: 59.15%), significantly larger than PMPs or sP-selectin alone.ConclusionsExpressions of PMPs, sP-selectin, EMPs and vWF Increased in NVAF patients with LASEC and that might be potential biomarkers for LASEC prediction.

Clinical Utility of Recently Food and Drug Administration-Approved IntelliSep Test (Sepsis Biomarker) for Early Diagnosis of Sepsis: Comparison with Other Biomarkers.

Context: IntelliSep by Cytovale has received United States (U.S.) Food and Drug Administration (FDA) approval as a sepsis biomarker test. However, the clinical utility of this new test is not assessed in emergency departments. Objective: We investigated the clinical utility of this test using 44 patients visiting the emergency department at The University of Kansas Medical Center by comparing it with the monocyte distribution width (MDW) and other biomarkers including the von Willebrand factor (vWF) and ADAMTS13. Design and Methods: IntelliSep assesses the cellular host response via deformability cytometry of biophysical leukocyte properties and produces a score (IntelliSep Index; ISI: from 0.1 (lowest risk) to 10 (highest risk). We measured the ISI in 44 patients (19 high probability and 25 low probability of sepsis groups) using EDTA-anticoagulated blood. Left over plasma was used for measuring the plasma von Willebrand factor (vWF) and ADAMTS13 antigen by ELISA assays. The MDW was obtained during routine CBC analysis using a Beckman hematology analyzer. The lactate and high-sensitivity troponin I levels were measured using a Beckman analyzer. Procalcitonin was measured using a Cobas e801 analyzer. Results: The median ISI was twofold higher in the high-probability group than in the low-probability group (p < 0.01) while the median MDW was 34.5% higher in the high-probability group than in the low-probability group (p < 0.01). However, the correlation between the ISI and MDW was only modest (r = 0.66). In addition, significantly higher levels of plasma vWF antigen but lower levels of plasma ADAMTS13 antigen in the high-probability group were found, resulting in significantly higher vWF/ADAMTS13 ratios in the high-probability group than in the low-probability group. Conclusions: The new IntelliSep test along with vWF/ADAMTS13 ratios may be useful for the early diagnosis of sepsis in patients visiting the emergency department, which appears to be superior to the traditional marker, MDW.

The aptamer BT200 blocks interaction of K1405-K1408 in the VWF-A1 domain with macrophage LRP1

Rondaptivon pegol (previously BT200) is a pegylated RNA aptamer that binds to the A1 domain of von Willebrand factor (VWF). Recent clinical trials demonstrated that BT200 significantly increased plasma VWF-factor VIII levels by attenuating VWF clearance. The biological mechanism(s) through which BT200 attenuates invivo clearance of VWF has not been defined. We hypothesized that BT200 interaction with the VWF-A1 domain may increase plasma VWF levels by attenuating macrophage-mediated clearance. We observed that full-length and VWF-A1A2A3 binding to macrophages and VWF-A1 domain binding to lipoprotein receptor-related protein 1 (LRP1) cluster II and cluster IV were concentration-dependently inhibited by BT200. Additionally, full-length VWF binding to LRP1 expressed on HEK293T (HEK-LRP1) cells was also inhibited by BT200. Importantly, BT200 interacts with the VWF-A1 domain in proximity to a conserved cluster of 4 lysine residues (K1405, K1406, K1407, and K1408). Alanine mutagenesis of this K1405-K1408 cluster (VWF-4A) significantly (P< .001) attenuated binding of VWF to both LRP1 clusters II and IV. Furthermore, invivo clearance of VWF-4A was significantly (P< .001) reduced than that of wild-type VWF. BT200 did not significantly inhibit binding of VWF-4A to LRP1 cluster IV or HEK-LRP1 cells. Finally, BT200 interaction with the VWF-A1 domain also inhibited binding to macrophage galactose lectin and the SR-AI scavenger receptor. Collectively, our findings demonstrate that BT200 prolongs VWF half-life by attenuating macrophage-mediated clearance and specifically the interaction of K1405-K1408 in the VWF-A1 domain with macrophage LRP1. These data support the concept that targeted inhibition of VWF clearance pathways represents a novel therapeutic approach for von Willebrand disease and hemophilia A.

Unravelling the spectrum of von Willebrand factor variants in quantitative von Willebrand disease: results from a German cohort study

Von Willebrand disease (VWD), the most prevalent hereditary bleeding disorder, results from deficiency of von Willebrand factor (VWF). This large cohort study aims to offer a comprehensive exploration of mutation spectra and laboratory features in quantitative VWF deficiencies, shedding light on genetic underpinnings and genotype-phenotype associations. Our cohort consisted of 221 Caucasian index patients with quantitative VWD, along with 47 individuals whose plasma VWF levels fell within the lower normal boundaries (50-70 IU/dL). We conducted comprehensive VWF assays and genetic analyses, encompassing VWF gene sequencing, copy number variation investigations, and bioinformatic assessments. Following International Society on Thrombosis and Haemostasis-Scientific and Standardization Committee VWF guidelines, 77 index patients were characterized as having type 1 VWD (VWF antigen [VWF:Ag]< 30 IU/dL), 111 as having type 1 VWD (VWF:Ag, 30-50 IU/dL), and 33 as having type 3 VWD. Mutation detection rates were 88%, 65%, and 92%, respectively. Notably, blood group O overrepresentation was evident in type 1 with VWF:Ag of 30 to 50 IU/dL, particularly among mutation-negative patients, suggesting a potential causal role of blood group O. A total of 223 VWF variants, comprising 147 distinct variations, were identified in quantitative VWD patients, of which 57 were novel variants (39%). Additionally, approximately 70% of individuals with VWF levels within the lower normal boundaries (50-70 IU/dL) displayed VWF variants. Our data advance our understanding of the molecular mechanisms underlying quantitative VWD, offering valuable insights for future research and clinical management. Distinct mutation patterns were observed among subgroups, particularly the contrast between type 1 VWD (VWF:Ag< 30 IU/dL) and type 1 VWD (VWF:Ag, 30-50 IU/dL), an area with limited prior investigation.

Implications of von Willebrand Factor in Inflammatory Bowel Diseases: Beyond Bleeding and Thrombosis.

Inflammatory bowel disease (IBD) displays an increased venous and arterial thrombotic risk despite the common occurrence of intestinal bleeding. While some of the mechanisms leading to these thrombotic complications have been studied, other specific changes in the hemostasis profile of IBD patients have been less explored. One such example relates to von Willebrand factor (VWF) whose plasma levels have been reported to be modulated in IBD. Von Willebrand factor is a plasma glycoprotein crucial for hemostatic functions via roles both in platelet function and coagulation. High plasma VWF is a known risk factor for venous thromboembolism. In addition to its canonical roles in hemostasis, VWF is known to be directly or indirectly involved in other vascular processes such as maintenance of endothelial barrier integrity or proliferation of vascular smooth muscle cells. The purpose of this review is to recapitulate and update the existing data about VWF biology in IBD and to highlight its role both in the existing procoagulant phenotype and in vascular alterations that may occur in IBD.

Plasma von Willebrand factor levels in patients with cancer: A meta‑analysis.

von Willebrand Factor (VWF) is well recognized for being dysregulated in various malignancies and has emerged as a potential biomarker for cancer detection. The present meta-analysis aimed to elucidate the association between plasma VWF and the incidence and metastasis of cancer. For this purpose, a comprehensive search was conducted across multiple databases from their inception until March 3, 2023. This culminated in the selection of 15 original studies on various types of cancer, including a collective sample of 1,403 individuals. The standardized mean difference (SMD) and 95% confidence intervals (CIs) were employed as statistical parameters to determine the association between plasma VWF and the incidence and metastasis of cancer. These were estimated using a random-effects model. The pooled data revealed that the plasma VWF levels of patients with cancer were significantly elevated compared with those of healthy controls (SMD, 0.98; 95% CI, 0.59-1.36), and a significant association was observed between plasma VWF levels and cancer metastasis (SMD, 0.69; 95% CI, 0.33-1.06). The symmetry of the Begg's funnel plots indicated that no significant bias was present in the analyses of VWF in cancer and its metastasis. In summary, the results of the present meta-analysis support the hypothesis that increased plasma VWF levels may serve as a biomarker for cancer and metastatic progression.

Isaridin E Protects against Sepsis by Inhibiting Von Willebrand Factor-Induced Endothelial Hyperpermeability and Platelet-Endothelium Interaction.

Endothelial hyperpermeability is pivotal in sepsis-associated multi-organ dysfunction. Increased von Willebrand factor (vWF) plasma levels, stemming from activated platelets and endothelium injury during sepsis, can bind to integrin αvβ3, exacerbating endothelial permeability. Hence, targeting this pathway presents a potential therapeutic avenue for sepsis. Recently, we identified isaridin E (ISE), a marine-derived fungal cyclohexadepsipeptide, as a promising antiplatelet and antithrombotic agent with a low bleeding risk. ISE's influence on septic mortality and sepsis-induced lung injury in a mouse model of sepsis, induced by caecal ligation and puncture, is investigated in this study. ISE dose-dependently improved survival rates, mitigating lung injury, thrombocytopenia, pulmonary endothelial permeability, and vascular inflammation in the mouse model. ISE markedly curtailed vWF release from activated platelets in septic mice by suppressing vesicle-associated membrane protein 8 and soluble N-ethylmaleide-sensitive factor attachment protein 23 overexpression. Moreover, ISE inhibited healthy human platelet adhesion to cultured lipopolysaccharide (LPS)-stimulated human umbilical vein endothelial cells (HUVECs), thereby significantly decreasing vWF secretion and endothelial hyperpermeability. Using cilengitide, a selective integrin αvβ3 inhibitor, it was found that ISE can improve endothelial hyperpermeability by inhibiting vWF binding to αvβ3. Activation of the integrin αvβ3-FAK/Src pathway likely underlies vWF-induced endothelial dysfunction in sepsis. In conclusion, ISE protects against sepsis by inhibiting endothelial hyperpermeability and platelet-endothelium interactions.