Von Willebrand factor deficiency and atherosclerosis

Von Willebrand factor (VWF) is a large multimeric glycoprotein that plays a major role in haemostasis, illustrated by the bleeding tendency in von Willebrand disease (VWD), the most common hereditary bleeding disorder caused by VWF deficiency or dysfunction. Elevated VWF levels are strongly associated with an increased risk of ischemic cardiovascular events. Whether this relation is causal, or whether increased VWF levels reflect disturbances of endothelial function remains to be elucidated. One possibility is that VWF participates in the process of atherogenesis. The aim of the current review is to determine whether VWF deficiency provides protection against the development of atherosclerosis in humans and animals. Results from animal studies suggest that, at arterial branch point predilection sites, VWF deficiency or blockage has a protective effect against atherosclerosis. Based on the available evidence, this potential protective effect of VWF deficiency can most likely be tracked to the VWF-platelet interaction. Sites involved in this interaction could prove attractive targets in future treatment and prevention of cardiovascular disease, an option that is already being explored in humans. An unequivocal protective effect of VWD on atherosclerosis has not been demonstrated in humans. However the interpretation of these results is hampered by several methodological weaknesses. In conclusion, VWF is probably a significant player in the multifaceted interaction between the haemostatic system and the atherosclerotic process which deserves further study.     

Von Willebrand Disease Lab Diagnosis

The hemorrhagic diseases are characterized by bleeding which can vary considerably according to their severity. The von Willebrand disease (VWD) is the most frequent hereditary hemorrhagic disease and the prevalence of clinically significant disease is probably closer to 1:1000, being an extremely heterogeneous and complex disorder that is related to the deficiency in concentration, structure or function of von Willebrand factor (VWF). The VWD is divided into type 1, with partial deficiency of the VWF, type 2, with qualitative defects in the molecule with four subdivisions, and type 3, with very low or undetectable levels of plasma and platelet VWF and ristocetin cofactor activity. The laboratory diagnosis of VWD is complex. Specific tests that assess the functionality and concentrations of the VWF and FVIII are needed. The routine tests are the bleeding time, the activated partial thromboplastin time and the platelet count, however, singly, they may not suggest the diagnosis of VWD, requiring further specific tests, such as VWF function evaluation through its ristocetin cofactor assay (VWF:RCo), VWF protein concentration immunoassay (VWF:Ag), the factor VIII coagulation assay (FVIII:C), VWF binding to immobilized collagen (VWF:CB), ristocetin-induced platelet aggregation (RIPA), VWF multimers patterns, factor VIII binding of immobilized VWF (VWF:FVIIIB), among others. From the moment the diagnosis is confirmed, the appropriate treatment for each patient is sought, with the purpose of increasing plasma concentrations of the deficient protein, both in bleeding episodes, as for invasive procedures. Although diagnosis facilitates treatment other approach in the present scenario is prenatal diagnosis which, is the need of the hour.     

Von Willebrand factor testing ratios in the diagnosis and subtyping of von Willebrand disease

Von Willebrand disease (VWD) is a common bleeding disorder of platelet adhesion with six currently recognized subtypes. Laboratory diagnosis consists of an initial test panel including antigen, activity and factor VIII measurements, sometimes followed by further specialized testing. VWF activity/antigen testing ratios help to differentiate type 1 and type 2 disease, which is important for selection of proper therapy. Recommended ratio cutoffs differ by guideline, ranging from 0.5 to 0.7, with 0.7 commonly recommended. The ratio cutoff used affects the sensitivity and specificity for type 2 diagnosis. Variability in VWD due to underlying mutations and patient factors, as well as variability in VWF tests, impact the accuracy of ratios for VWD subtyping. This review discusses the use of activity/antigen ratios in the diagnosis and subtyping of VWD with a focus on technical aspects of the tests.     

血管性血友病因子及其裂解酶在肺癌患者中的表达及其意义

目的探讨肺癌患者在不同病理状态下血管性血友病因子(vWF)水平及其裂解酶(vWF-cp)活性的改变及临床意义。方法以残余胶原结合实验及ELISA分别测定2003年10月至2005年1月苏州大学附属第一医院呼吸科78例肺癌血浆vWF-cp和vWF,对其中23例合并胸腔积液的肺癌患者以放免法测定血清和胸水癌胚抗原(CEA)水平。结果(1)肺癌患者vWF抗原(vWFAg)(107.7±43.7)%显著高于正常对照组(71.3±49.5)%及肺良性疾病组(82.4±41.3)%(P<0.05),而vWF-cp活性水平在肺癌患者(59.2±21.5)%显著低于正常对照组(86.6±1.8)%和肺良性疾病组(79.4±13.3)%(P<0.05);二者在肺癌晚期广泛转移较局限期差异均有显著性;(2)血浆vWFAg与胸水CEA呈正相关,而vWF-cp与胸水CEA呈负相关。结论肺癌患者血浆vWFAg升高、vWF-cp降低,并与疾病进展有关。     

Prophylaxis in von Willebrand disease

Von Willebrand disease (VWD), the most common hereditary bleeding disorder, is divided into three types depending on the quantitative (type 1 and 3) or qualitative (type 2) abnormality of von Willebrand factor (VWF). About 70–80% of VWD patients can be treated with the synthetic product desmopressin, while the others necessitate factor VIII/VWF concentrates. In addition to the treatment of bleeding episodes, therapeutic regimens include short- or long-term prophylaxis. While the literature data on short-term prophylaxis in VWD are consistent and clearly show the safety and efficacy of such a therapeutic approach, little evidence is available regarding long-term prophylaxis, and although the preliminary results are encouraging, they need to be validated by large prospective studies.     

心脏起搏早期对血浆血管性假性血友病因子和可溶性P-选择素的影响及意义

探讨心脏起搏早期对血浆血管性假性血友病因子 (VWF)和可溶性P 选择素 (SPS)的影响及其意义。对 32例不同方式起搏患者及 2 0例对照者采用酶联免疫双抗夹心法测定术前及术后 7～ 8天的VWF及SPS。结果 :心脏起搏患者术前存在高水平的VWF、SPS ,术后血浆VWF及SPS随临床症状的改善而显著下降 ,但仍高于正常对照。结论 :心脏起搏早期明显降低血浆VWF及SPS水平 ,由于血浆VWF、SPS分别是反映血管内皮功能和血小板活性的特异敏感分子标志物 ,因此 ,心脏起搏早期在改善临床症状的同时伴有血管内皮功能的改善和血小板活性的降低。而起搏患者术前、术后高水平的VWF、SPS可能是术后的起搏患者静脉血栓形成的病理基础     

Impact of transcatheter aortic valve implantation on circulating von Willebrand factor in patients with severe aortic stenosis

Introduction

Severe aortic stenosis (AS) can lead to degradation of high molecular weight (HMW) von Willebrand factor (VWF) which can result in haemostatic abnormalities. While studies have explored changes in VWF profiles before and after surgical aortic valve replacement (SAVR), the longer-term changes in VWF profiles pre- and post-transcatheter aortic valve implantation (TAVI) are less understood.

Aim

Our primary objective was to identify differences in VWF multimer profiles and VWF function pre-TAVI and 1-month post-TAVI. Our secondary objective was to correlate VWF markers with measures of AS severity.

Methods

Adult patients with severe AS referred for TAVI at our institution were prospectively enrolled in this cohort study. Blood samples were collected for plasma analysis at three time points for all patients: 1 day pre-TAVI, 3 days post-TAVI, and 1-month post-TAVI. VWF antigen, activity, propeptide, collagen binding, multimers, and factor VIII coagulant activity were determined at each time point. Correlations between VWF parameters and severity of AS were assessed.

Results

Twenty participants (15 males, five females) with severe AS were recruited for the study. There was a significant increase in HMW VWF between pre-procedure and 1-month post-TAVI (p < .05). There was a transient increase in VWF antigen levels and activity at 3-days post TAVI that decreased to pre-TAVI levels at 1-month. There were no statistically significant correlations between VWF markers and AS severity.

Conclusions

This is the first study to elucidate longer-term (>1 week) improvements in HMW VWF after a TAVI procedure in severe AS patients.     

Von Willebrand factor propeptide makes it easy to identify the shorter Von Willebrand factor survival in patients with type 1 and type Vicenza von Willebrand disease

Reduced von Willebrand factor (VWF) half-life has been suggested as a new pathogenic mechanism in von Willebrand disease (VWD). The usefulness of VWF propeptide (VWFpp) in exploring VWF half-life was assessed in 22 type 1 and 14 type Vicenza VWD patients, and in 30 normal subjects, by comparing the findings on post-Desmopressin (DDAVP) VWF t(1/2) elimination (t(1/2el)). The VWFpp/VWF antigen ratio (VWFpp ratio) was dramatically increased in type Vicenza VWD (13.02 +/- 0.49) when compared to normal subjects (1.45 +/- 0.06), whereas it appeared to be normal in all type 1 VWD patients (1.56 +/- 0.7), except for the four carrying the C1130F mutation (4.69 +/- 0.67). A very short VWF t(1/2el) was found in type Vicenza VWD (1.3 +/- 0.2 h), while all type 1 VWD patients had a t(1/2el) similar to that of the controls (11.6 +/- 1.4 and 15.4 +/- 2.5 h respectively), except for the four patients carrying the C1130F mutation, who had a significantly shorter VWF survival (4.1 +/- 0.2 h). A significant inverse correlation emerged between VWFpp ratio and VWF t(1/2el) in both VWD patients and normal subjects. The VWFpp ratio thus seemed very useful for distinguishing between type 1 VWD cases with a normal and a reduced VWF survival, as well as for identifying type Vicenza VWD.     

Changing insights in the diagnosis and classification of autosomal recessive and dominant von Willebrand diseases 1980-2015

The European Clinical Laboratory and Molecular (ECLM) criteria define 10 distinct Willebrand diseases (VWD): recessive type 3, severe 1, 2C and 2N; dominant VWD type 1 secretion/clearance defect, 2A, 2B, 2E, 2M and 2D; and mild type 1 VWD (usually carriers of recessive VWD). Recessive severe 1 and 2C VWD are characterized by secretion and multimerization defects caused by mutations in the D1-D2 domain. Recessive 2N VWD is a mild hemophilia due to D’-FVIII-von Willebrand factor (VWF) binding site mutations. Dominant 2E VWD caused by heterozygous missense mutations in the D3 domain is featured by a secretion-clearance-multimerization VWF defect. Dominant VWD type 2M due to loss of function mutations in the A1 domain is characterized by decreased ristocetin-induced platelet aggregation and VWF:RCo, normal VWF multimers and VWF:CB, a poor response of VWF:RCo and good response of VWF:CB to desmopressin (DDAVP). Dominant VWD type 2A induced by heterozygous mutations in the A2 domain results in hypersensitivity of VWF for proteolysis by ADAMTS13 into VWF degradation products, resulting in loss of large VWF multimers with triplet structure of each individual VWF band. Dominant VWD type 2B due to a gain of function mutation in the A1 domain is featured by spontaneous interaction between platelet glycoprotein Ib (GPIb) and mutated VWF A1 followed by increased proteolysis with loss of large VWF multimers and presence of each VWF band. A new category of dominant VWD type 1 secretion or clearance defect due to mutations in the D3 domain or D4-C1-C5 domains consists of two groups: Those with normal or smeary pattern of VWF multimers.     

Von Willebrand factor: molecular size and functional activity

 Von Willebrand factor (vWF) is the largest protein found in plasma. It circulates in blood as a series of multimers ranging in size from 500 to 20 000 kDa. The variable molecular weight of vWF is due to differences in the number of subunits comprising the protein. vWF mediates platelet adhesion to subendothelium of the damaged blood vessel. Only the largest multimers are hemostatically active. Each vWF subunit contains binding sites for collagen and for platelet glycoproteins GPIb and GPIIb/IIIa. Multiple interactions of repeating binding sites in vWF multimers with adhesive protein(s) of the subendothelium and with receptors on the platelet surface lead to "irreversible" binding of platelets to the exposed subendothelium. Functional properties of vWF are typical of multisubunit proteins encoded by autosomal loci. The phenotype of von Willebrand disease is determined by the properties of the dysfunctional subunits which become incorporated into heteropolymeric forms of vWF. Absence of large vWF multimers, seen in type 2A von Willebrand disease and in myeloproliferative disorders, is associated with bleeding tendency. On the other hand, in patients with vWF multimers of supranormal size, as they occur in thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), there is an increased risk of thrombosis. Proteolytic enzyme(s) are involved in physiologic regulation of the polymeric size of vWF. We have purified from human plasma a protease cleaving vWF at the same peptide bond that is also cleaved in vivo. vWF was quite resistant against the protease in a physiologic buffer but was degraded at low salt concentration or in the presence of 1 M urea. It appears that a conformational change in the vWF molecule exposes the specific protease-sensitive peptide bond and thus enhances degradation of vWF multimers. In some variants of type 2A vWF, the cleavage site in the vWF subunit is more susceptible to proteolytic degradation than in normal vWF, whereas in patients with TTP or HUS the protease activity may be suppressed. vWF-degrading protease plays an important role in pathogenesis of congenital or acquired disorders of hemostasis and thrombosis. Received: 7 March 1996 / Accepted: 13 March 1996     

Plasma Von Willebrand Factor Levels Predict Survival in COVID-19 Patients Across the Entire Spectrum of Disease Severity

Background: Characterization of reticulo-endothelial activation in COVID-19 may guide treatment. Objectives: To assess reticulo-endothelial activation and its correlation with disease severity and death in patients across the entire spectrum of COVID-19 severity. Methods: Consecutive hospitalized COVID-19 patients were studied, with similar number of patients in each disease severity category. Baseline serum ferritin, sCD163 (macrophage activation markers) and plasma von Willebrand factor (VWF) antigen (endothelial activation marker) levels were studied. Clinical parameters and plasma D-dimer levels were also studied. The study parameters were correlated with COVID-19 severity and survival. Results: The 143 patients (104 males [80%], age 54 [42 – 65] years, median [inter-quartile range]) presented 4 (3—7) days after symptom onset. Thirty-four patients had mild disease, 36 had moderate disease, 36 had severe disease and 37 had critical disease at baseline. With increasing COVID-19 severity, ferritin, sCD163, VWF and D-dimer levels significantly increased at baseline, however, 139 patients had normal sCD163 levels. Of the reticulo-endothelial markers, VWF level independently correlated with COVID-19 severity and with survival. VWF level > 332.6 units/dl correlated with COVID-19 severity (odds ratio [OR]: 2.77 [95% confidence interval (C.I): 1.1 – 6.99], p value: 0.031) and in-hospital death (OR [95% CI]: 29.28 [5.2 – 165], p value < 0.001). Conclusions: Reticulo-endothelial activation markers increased incrementally with worsening COVID-19 severity. Baseline endothelial activation marker (VWF), and not macrophage activation markers, independently correlated with COVID-19 severity and death.     

心肺复苏后72h内监测血管性血友病因子凝血的临床意义

目的:探讨心脏骤停心肺复苏(CPR)后72h内血管性血友病因子(VWF)凝血的动态变化及意义。方法:35例心脏骤停心肺复苏患者,依复苏最终效果分为A1组25例:初期复苏成功,自主循环(ROSC)建立≥72h但最终死亡;A2组10例:复苏成功,存活出院。于ROSC24h、48h及72h检测VWF、D-二聚体(D-dimer)、凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)水平的动态变化。结果:A1组ROSC24hVWF、D-D、PT及APTT水平高于A2组(P0.05),ROSC48h各项指标水平变化达峰值且A1高于A2组;ROSC72hA2组各项指标明显改善与A1组比较差异有统计学意义(P0.05)。结论:心跳骤停成功心肺复苏患者存在VWF以及内源外源性凝血功能紊乱。其变化对病情严重程度及预后有重要的判断价值。