Are serum autoantibodies associated with brain changes in systemic lupus erythematosus? MRI data from the Leiden NP-SLE cohort.

OBJECTIVE: The effect of serum autoantibodies on the brain of systemic lupus erythematosus (SLE) patients remains unclear. We investigated whether serum autoantibodies, individually and assessed in groups, are associated with specific brain-MRI abnormalities or whether these structural changes are associated with other SLE-related or traditional cardiovascular disease risk factors. METHODS: All patients underwent brain 3Tesla-MRI. White matter hyperintensities (WMHs), ischemic lesions, inflammatory-like lesions and cerebral atrophy were scored. Serum autoantibodies analyzed included lupus anticoagulant (LAC), anticardiolipine (aCL) IgG and IgM (first 3 also grouped into antiphospholipid autoantibodies (aPL)), anti-dsDNA, anti-SSA, anti-SSB, anti-RNP, and anti-Sm (the latter 5 grouped into SLE-related autoantibodies). Associations were assessed using logistic regression analysis adjusted for potential confounders. Furthermore, a sensitivity analysis including anti-Beta2 glycoprotein-1 antibodies (anti-ß2GP1) in the aPL group was performed and the potential modification role of the neuropsychiatric clinical status in the model was assessed. RESULTS: 325 patients (mean age 42 years (SD 14), 89% female) were included. The following MRI-brain abnormalities were found: WMHs (71%), lacunar infarcts (21%), gliosis (11%), micro-hemorrhages (5%), large hemorrhages (2%), inflammatory-like lesions (6%) and atrophy (14%). No associations were found between individual or total SLE-related autoantibodies and inflammatory-like lesions. A higher number of positive aPL was associated with lacunar infarcts (OR 1.37 (95%CI 1.02-1.99) and gliosis (OR 2.15 (1.37-3.37)). LAC was associated with lacunar infarcts in white matter (OR 3.38 (1.32-8.68)) and atrophy (OR 2.49 (1.01-6.15)), and aCL IgG with gliosis (OR 2.71 (1.05-7.02)). Among other variables, SLE patients with hypertension presented a higher chance for WMHs (OR 5.61 (2.52-12.48)) and lacunar infarcts in WM (OR 2.52 (1.10-5.74)) and basal ganglia (OR 8.34 (2.19-31.70)), while cumulative SLE-damage was correlated with lacunar infarcts in WM (OR 1.43 (1.07-1.90)), basal ganglia (OR 1.72 (1.18-2.51)) and cerebellum (OR 1.79 (1.33-2.41)). These associations were confirmed in the sensitivity analysis. CONCLUSIONS: Brain abnormalities in SLE represent different underlying pathogenic mechanisms. aPL are associated with ischemic brain changes in SLE, while the presence of SLE-related serum autoantibodies is not related to inflammatory-like lesions. Hypertension and cumulative SLE-damage associate with ischemic MRI-brain changes in SLE, suggesting the importance of accelerated atherosclerosis in this process.

Analysis of current perioperative management with Haemate® P/Humate P® in von Willebrand disease: Identifying the need for personalized treatment.

INTRODUCTION: Patients with Von Willebrand disease (VWD) are regularly treated with VWF-containing concentrates in case of acute bleeding, trauma and dental or surgical procedures. AIM: In this multicentre retrospective study, current perioperative management with a von Willebrand factor (VWF)/Factor VIII (FVIII) concentrate (Haemate® P) in patients with VWD was evaluated. PATIENTS/METHODS: Patients with VWD undergoing minor or major surgery between 2000 and 2015, requiring treatment with a VWF/FVIII concentrate (Haemate® P), were included. Achieved VWF activity (VWF:Act) and FVIII during FVIII-based treatment regimens were compared to predefined target levels in national guidelines. RESULTS: In total, 103 patients with VWD (148 surgeries) were included: 54 type 1 (73 surgeries), 43 type 2 (67 surgeries) and 6 type 3 (8 surgeries). Overall, treatment resulted in high VWF:Act and FVIII levels, defined as ≥0.20 IU/mL above predefined levels. In patients with type 1 VWD, respectively, 65% and 91% of trough VWF:Act and FVIII levels were higher than target levels. In patients with type 2 and type 3 VWD, respectively, 53% and 57% of trough VWF:Act and 72% and 73% of trough FVIII levels were higher than target level. Furthermore, FVIII accumulation over time was observed, while VWF:Act showed a declining trend, leading to significantly higher levels of FVIII than VWF:Act. CONCLUSION: High VWF:Act and accumulation of FVIII were observed after perioperative FVIII-based replacement therapy in patients with VWD, both underlining the necessity of personalization of dosing regimens to optimize perioperative treatment.

Health-related quality of life, developmental milestones, and self-esteem in young adults with bleeding disorders.

BACKGROUND: The treatment of bleeding disorders improved in the last decades. However, the effect of growing up with bleeding disorders on developmental, emotional, and social aspects is understudied. Therefore, this study assesses HRQOL, developmental milestones, and self-esteem in Dutch young adults (YA) with bleeding disorders compared to peers. METHODS: Ninety-five YA (18-30 years) with bleeding disorders (78 men; mean 24.7 years, SD 3.5) and 17 women (mean 25.1 years, SD 3.8) participated and completed the Pediatric Quality of Life Inventory Young Adult version, the Course of Life Questionnaire, and the Rosenberg Self-Esteem Scale. Differences between patients with bleeding disorders and their peers, and between hemophilia severity groups, were tested using Mann-Whitney U tests. RESULTS: YA men with bleeding disorders report a slightly lower HRQOL on the total scale, physical functioning, and school/work functioning in comparison to healthy peers (small effect sizes). YA men with severe hemophilia report more problems on the physical functioning scale than non-severe hemophilia. YA men with bleeding disorders achieved more psychosexual developmental milestones than peers, but show a delay in 'paid jobs, during middle and/or high school.' A somewhat lower self-esteem was found in YA men with bleeding disorders in comparison to peers (small effect size). For YA women with bleeding disorders, no differences were found on any of the outcomes in comparison to peers. CONCLUSION: This study demonstrates some impairments in HRQOL and self-esteem in YA men with bleeding disorders. By monitoring HRQOL, problems can be identified early, especially with regard to their physical and professional/school functioning.

Plasma levels of plasminogen activator inhibitor-1 and bleeding phenotype in patients with von Willebrand disease.

INTRODUCTION: von Willebrand disease (VWD) is the most common inherited bleeding disorder. In VWD patients, large variations in bleeding tendency are observed, which cannot be completely explained by the variation in von Willebrand factor levels or activities. Thus, there must be additional factors, for instance, changes in fibrinolysis that have an effect on the variation in bleeding tendency in VWD patients. AIM: To investigate whether plasminogen activator inhibitor-1 (PAI-1) level influences the variation in bleeding tendency in VWD patients. METHODS: PAI-1 antigen levels were measured in the plasma of 633 patients with moderate or severe VWD who participated in the 'Willebrand in the Netherlands' (WiN) study, a nationwide multicentre cross-sectional study. Bleeding severity was assessed using the Tosetto bleeding score. RESULTS: PAI-1 levels increased with age (Spearman's rho: 0.225, P < 0.001) and were higher in men (23 [IQR 12-60] vs. 20 [IQR 10-44] ng mL-1 in women, P = 0.039), whereas the bleeding score was higher in women (11 [IQR 7-17] vs. 9 [IQR 5-14] ng mL-1 in men, P = 0.002). After adjustment for age and sex by stratification, PAI-1 level and bleeding score were negatively correlated (Spearman's rho: -0.170, P = 0.017) in the group of 196 young (age ≤ 45 year) female VWD patients, accounting for 31% of our study population. CONCLUSION: In young female VWD patients, we observed that low PAI-1 levels were associated with a higher bleeding score, which may partly explain the observed variability in bleeding phenotype in VWD patients.

Comparison of haemostatic function of PAS-C-platelets vs. plasma-platelets in reconstituted whole blood using impedance aggregometry and thromboelastography.

BACKGROUND AND OBJECTIVES: There are concerns about the haemostatic function of platelets stored in platelet additive solution (PAS). Aim of this study was to compare the haemostatic function of PAS-C-platelets to plasma-platelets in reconstituted whole blood. MATERIALS AND METHODS: In our experiment, whole blood was reconstituted with red blood cells, solvent-detergent (SD) plasma and either PAS-C-platelets or plasma-platelets (n = 7) in a physiological ratio. On storage days 2, 5, 8 and 13, the agonist-induced aggregation (multiple electrode aggregometry), clot formation (thromboelastography) and agonist-induced CD62P responsiveness (flow cytometry) were measured. RESULTS: Samples with PAS-C-platelets showed significantly lower aggregation than plasma-platelets when induced with adenosine diphosphate, -6 U (95% confidence interval: -8; -4) or thrombin receptor-activating protein, -15 U (-19; -10). Also when activated with collagen and ristocetin, the PAS-C-platelets showed less aggregation, although not statistically significant. All samples with PAS-C-platelets showed significantly lower agonist-induced CD62P responsiveness than samples with plasma-platelets. However, there was no difference regarding all TEG parameters. CONCLUSION: Our findings demonstrate that the function - aggregation and CD62P responsiveness - of PAS-C-platelets in reconstituted whole blood is inferior to that of plasma-platelets, which may have implications in the setting of massive transfusions.

State of the art: von Willebrand disease.

The State of the Art in von Willebrand disease (VWD) has been impacted not only by discoveries in the field of haemostasis, but also by changes in practice in other fields. The development of bleeding assessment tools has led to the clarification of bleeding symptoms and phenotype in VWD. New discoveries in the biology and genetics of von Willebrand factor (VWF) are challenging our existing diagnostics and classification(s). An improved understanding of reproductive physiology and the pathology of VWD along with changing obstetric, gynaecologic and haemostatic therapies necessitate an evolving response to the care of women with VWD. The survival of patients with autoimmune disease, malignancies and congenital heart disease along with increasing use of circulatory support devices and extracorporeal membrane oxygenation is increasing the prevalence of acquired von Willebrand syndrome. In each of these challenges, there are opportunities to improve the care of our patients with VWD.

Joint surgery in von Willebrand disease: a multicentre cross-sectional study.

BACKGROUND: Joint bleeds are reported by 23% of von Willebrand disease (VWD) patients and associated with orthopaedic surgery. Limited data are available on joint surgery in VWD. AIM: To assess the prevalence, indications, management and complications of joint surgery in VWD patients. METHODS: 804 VWD patients with historically lowest von Willebrand factor (VWF) activity ≤30 U dL-1 completed a questionnaire on joint bleeds, joint damage and orthopaedic surgery. We retrieved additional medical file data of patients who underwent surgery on large joints (shoulder, elbow, hip, knee or ankle). RESULTS: 116 out of 804 patients (14%) reported large joint surgery. Compared to VWD patients without previous orthopaedic surgery, these 116 patients reported more frequently a history of joint bleeds and joint damage (41% vs. 20%, P < 0.001 and 61% vs. 20%, P < 0.001). Medical file data on 126 large joint surgeries in 79 VWD patients revealed that this surgery was associated with joint damage due to prior joint bleeds in 24% of the procedures. Preoperative clotting factor correction (CFC) to prevent bleeding was administered in most cases (81%). Documentation on postoperative bleeding was found in 23 surgeries (18%). CONCLUSIONS: Large joint surgery is reported by 14% of VWD patients, related to joint bleeds in 24% and seems associated with bleeding complications frequently despite perioperative CFC.

Primary postpartum haemorrhage in women with von Willebrand disease or carriership of haemophilia despite specialised care: a retrospective survey.

Pregnant women with bleeding disorders require specialised peripartum care to prevent postpartum haemorrhage (PPH). If third trimester coagulation factor levels are <0.50 IU mL(-1) , prophylactic treatment is indicated and administered according to international guidelines. However, optimal dose and duration are unknown and bleeding may still occur. The aim of this study was to investigate the outcome in women with von Willebrand disease (VWD) or haemophilia carriership treated according to current practice guidelines. From the period 2002-2011, 185 deliveries in 154 VWD women or haemophilia carriers were retrospectively included. Data on blood loss, bleeding disorder characteristics and obstetric risk factors were obtained. The outcome was primary PPH, defined as blood loss ≥500 mL within 24 h postpartum and severe PPH as blood loss ≥1000 mL. Primary PPH was observed in 62 deliveries (34%), 14 (8%) of which resulted in severe PPH. In 26 deliveries prophylactic treatment was administered due to factor levels below the 0.50 IU mL(-1) cut-off in the third trimester, 14 of which (54%) were complicated by PPH. We found an increased PPH risk in deliveries given prophylactic treatment compared with deliveries without (OR 2.7, 95% CI 1.2-6.3). In conclusion, PPH incidence was highest in deliveries with the lowest factor levels in the third trimester. Currently, delivery outcome in women with bleeding disorders is unsatisfactory, given the high PPH incidence despite specialised care. Future studies are required to optimise management of deliveries in this patient population.

Joint bleeds in von Willebrand disease patients have significant impact on quality of life and joint integrity: a cross-sectional study.

BACKGROUND: Joint bleeds (JB) are reported in a minority of patients with von Willebrand disease (VWD) but may lead to structural joint damage. Prevalence, severity and impact of JB in VWD are largely unknown. OBJECTIVES: The aim of this study was to assess JB prevalence, onset, treatment and impact on health-related quality of life (HR-QoL) and joint integrity in moderate and severe VWD. METHODS: In the Willebrand in the Netherlands study 804 moderate and severe VWD patients [von Willebrand factor (VWF) activity ≤30U dL(-1)] completed a questionnaire on occurrence, sites and consequences of JB. To analyse JB number, onset, treatment and impact on joint integrity we additionally performed a patient-control study on medical file data comparing patients with JB to age, gender, factor VIII (FVIII)- and VWF activity matched VWD patients without JB. RESULTS: Of all VWD patients 23% (184/804) self-reported JB. These 184 patients reported joint damage more often (54% vs. 18%, P < 0.001) and had lower HR-QoL (SF36, P < 0.05) compared to VWD patients not reporting JB. Of 55 patients with available JB data, 65% had the first JB before age 16. These 55 patients used more clotting factor concentrate (CFC; median dose 43 vs. 0 IE FVIII kg(-1) year(-1) , P < 0.001), more often had X-ray joint damage (44% vs. 11%, P = 0.001] and chronic joint pain (44% vs. 18%, P = 0.008) compared to 55 control VWD patients without JB. CONCLUSION: In conclusion, joint bleeds are reported by 23% of moderate and severe VWD patients, mostly start in childhood, are associated with more CFC use, joint pain, lower HR-QoL and significantly more radiological and self-reported joint damage.

Towards the imaging of Weibel-Palade body biogenesis by serial block face-scanning electron microscopy.

Electron microscopy is used in biological research to study the ultrastructure at high resolution to obtain information on specific cellular processes. Serial block face-scanning electron microscopy is a relatively novel electron microscopy imaging technique that allows three-dimensional characterization of the ultrastructure in both tissues and cells by measuring volumes of thousands of cubic micrometres yet at nanometre-scale resolution. In the scanning electron microscope, repeatedly an image is acquired followed by the removal of a thin layer resin embedded biological material by either a microtome or a focused ion beam. In this way, each recorded image contains novel structural information which can be used for three-dimensional analysis. Here, we explore focused ion beam facilitated serial block face-scanning electron microscopy to study the endothelial cell-specific storage organelles, the Weibel-Palade bodies, during their biogenesis at the Golgi apparatus. Weibel-Palade bodies predominantly contain the coagulation protein Von Willebrand factor which is secreted by the cell upon vascular damage. Using focused ion beam facilitated serial block face-scanning electron microscopy we show that the technique has the sensitivity to clearly reveal subcellular details like mitochondrial cristae and small vesicles with a diameter of about 50 nm. Also, we reveal numerous associations between Weibel-Palade bodies and Golgi stacks which became conceivable in large-scale three-dimensional data. We demonstrate that serial block face-scanning electron microscopy is a promising tool that offers an alternative for electron tomography to study subcellular organelle interactions in the context of a complete cell.

Tachyphylaxis and reproducibility of desmopressin response in perioperative persons with nonsevere hemophilia A: implications for clinical practice.

Background: Desmopressin is frequently used perioperatively in persons with nonsevere hemophilia A. However, increase in factor (F)VIII:C after desmopressin use is interindividually highly variable. Tachyphylaxis has only been reported in test setting for persons with hemophilia A, with a remaining response of approximately 70% after a second dose compared with that after a first dose. Objectives: To study tachyphylaxis of FVIII:C response after multiple administration(s) of desmopressin in perioperative persons with nonsevere hemophilia A. Methods: We studied FVIII:C levels after desmopressin before (day 0 [D0]) and on days 1 (D1) and 2 (D2) after surgery in 26 patients of the DAVID and Little DAVID studies. We studied tachyphylaxis by comparing the responses at D1 and D2 with that at D0. We also assessed the reproducibility of the D0 response in comparison to an earlier performed desmopressin test. Results: The median absolute FVIII:C increase was 0.50 IU/mL (0.35-0.74; n = 23) at D0, 0.21 IU/mL (0.14-0.28; n = 17) at D1, and 0.23 IU/mL (0.16-0.30; n = 11) at D2. The median percentage of FVIII increase after the second administration (D1) compared with the first (D0) was 42.9% (29.2%-52.5%; n = 17) and that of the third (D2) compared with the first (D0) was 36.4% (23.7%-46.9%; n = 11). The FVIII:C desmopressin response at D0 was comparable with the desmopressin test response in 74% of the patients. Conclusion: Tachyphylaxis in the surgical setting was considerably more pronounced than previously reported, with FVIII:C at D1 and D2 of 36% to 43% of the initial response. Our results may have important implications for monitoring repeated desmopressin treatment when used perioperatively.

Maternal and neonatal bleeding complications in relation to peripartum management in hemophilia carriers: A systematic review.

Currently, there is no consensus on the optimal management to prevent postpartum hemorrhage (PPH) in hemophilia carriers. We aimed to evaluate peripartum management strategies in relation to maternal and neonatal bleeding outcomes by performing an extensive database search up to August 2020. Seventeen case-reports/series and 11 cohort studies were identified of overall 'poor' quality describing 502 deliveries. The PPH incidence in the individual patient data was 63%; 44% for those women receiving prophylaxis to correct coagulation and 77% for those without (OR 0.23, CI 0.09-0.58) and in cohort data 20.3% (26.8% (11/41) vs. 19.4% (55/284) (OR: 1.53, 95% CI: 0.72-3.24), respectively. Peripartum management strategies mostly consisted of clotting factor concentrates, rarely of desmopressin or plasma. Tranexamic acid appears promising in preventing secondary PPH, but was not used consistently. Neonatal bleeding was described in 6 affected male neonates, mostly after instrumental delivery or emergency CS, but insufficient information was provided to reliably investigate neonatal outcome in relation to management. The high PPH risk seems apparent, at most mildly attenuated by prophylactic treatment. Prospective cohort studies are needed to determine the optimal perinatal management in hemophilia.

Von Willebrand disease and Weibel-Palade bodies.

Von Willebrand factor (VWF) is a pivotal haemostatic protein mediating platelet adhesion to injured endothelium and carrying coagulation factor VIII (FVIII) in the circulation to protect it from premature clearance. Apart from the roles in haemostasis, VWF drives the formation of the endothelial cell specific Weibel-Palade bodies (WPBs), which serve as a regulated storage of VWF and other thrombotic and inflammatory factors. Defects in VWF could lead to the bleeding disorder von Willebrand disease (VWD). Extensive studies have shown that several mutations identified in VWD patients cause an intracellular retention of VWF. However, the effects of such mutations on the formation and function of its storage organelle are largely unknown. This review gives an overview on the role of VWF in WPB biogenesis and summarizes the limited data on the WPBs formed by VWD-causing mutant VWF.

Clinical and computed tomography characteristics of COVID-19 associated acute pulmonary embolism: A different phenotype of thrombotic disease?

INTRODUCTION: COVID-19 infections are associated with a high prevalence of venous thromboembolism, particularly pulmonary embolism (PE). It is suggested that COVID-19 associated PE represents in situ immunothrombosis rather than venous thromboembolism, although the origin of thrombotic lesions in COVID-19 patients remains largely unknown. METHODS: In this study, we assessed the clinical and computed tomography (CT) characteristics of PE in 23 consecutive patients with COVID-19 pneumonia and compared these to those of 100 consecutive control patients diagnosed with acute PE before the COVID-19 outbreak. Specifically, RV/LV diameter ratio, pulmonary artery trunk diameter and total thrombus load (according to Qanadli score) were measured and compared. RESULTS: We observed that all thrombotic lesions in COVID-19 patients were found to be in lung parenchyma affected by COVID-19. Also, the thrombus load was lower in COVID-19 patients (Qanadli score -8%, 95% confidence interval [95%CI] -16 to -0.36%) as was the prevalence of the most proximal PE in the main/lobar pulmonary artery (17% versus 47%; -30%, 95%CI -44% to -8.2). Moreover, the mean RV/LV ratio (mean difference -0.23, 95%CI -0.39 to -0.07) and the prevalence of RV/LV ratio >1.0 (prevalence difference -23%, 95%CI -41 to -0.86%) were lower in the COVID-19 patients. CONCLUSION: Our findings therefore suggest that the phenotype of COVID-19 associated PE indeed differs from PE in patients without COVID-19, fuelling the discussion on its pathophysiology.

Maternal and neonatal bleeding complications in relation to peripartum management in women with Von Willebrand disease: A systematic review.

Women with Von Willebrand disease (VWD) have an increased risk of developing postpartum hemorrhage (PPH). Our aim is to evaluate peripartum management strategies in relation to maternal and neonatal bleeding complications in VWD. Electronic databases were searched up to January 2019. Seventy-one case-reports and -series and 16 cohort studies were selected, including 811 deliveries. Cohort studies reported primary PPH in 32% and secondary PPH in 13% of the women. The overall primary PPH incidence in the individual patient data was 34%, similar between women who received prophylactic treatment to prevent PPH and those who didn't. Neonatal bleeding events were reported in 4.6% of deliveries. Overall, the available evidence on peripartum management in women with VWD was of low quality. The ongoing high risk for PPH is evident, despite prophylactic treatment, as well as the need for higher quality evidence from larger prospective cohort studies to improve management strategies.

Acquired haemophilia A in a patient with breast cancer and lung carcinoma: a case report and literature review.

Acquired haemophilia A is a rare disorder caused by spontaneous formation of auto-antibodies (inhibitors) against coagulation factor VIII. This can lead tolife-threatening haemorrhages. Six to twenty-two percent of patients with acquired haemophilia have an underlying malignancy. We describe a 69-year-old woman with metastatic breast cancer and non-small cell lung carcinoma who presented at the emergency room with spontaneous bruising, and who was using a vitamin K antagonist. She had a prolonged activated partial thromboplastin time (aPTT) due to a coagulation factor VIII deficiency caused by factor VIII antibodies. She was treated with prednisone and cyclophosphamide.

Diagnosing and treating antiphospholipid syndrome: a consensus paper.

INTRODUCTION: The antiphospholipid syndrome (APS) is defined by the occurrence of venous and/or arterial thrombosis and/or pregnancy-related morbidity, combined with the presence of antiphospholipid antibodies (aPL) and/or a lupus anticoagulant (LAC). Large, controlled, intervention trials in APS are limited. This paper aims to provide clinicians with an expert consensus on the management of APS. METHODS: Relevant papers were identified by literature search. Statements on diagnostics and treatment were extracted. During two consensus meetings, statements were discussed, followed by a Delphi procedure. Subsequently, a final paper was written. RESULTS: Diagnosis of APS includes the combination of thrombotic events and presence of aPL. Risk stratification on an individual base remains challenging. 'Triple positive' patients have highest risk of recurrent thrombosis. aPL titres > 99th percentile should be considered positive. No gold standard exists for aPL testing; guidance on assay characteristics as formulated by the International Society on Thrombosis and Haemostasis should be followed. Treatment with vitamin K-antagonists (VKA) with INR 2.0-3.0 is first-line treatment for a first or recurrent APS-related venous thrombotic event. Patients with first arterial thrombosis should be treated with clopidogrel or VKA with target INR 2.0-3.0. Treatment with direct oral anticoagulants is not recommended. Patients with catastrophic APS, recurrent thrombotic events or recurrent pregnancy morbidity should be referred to an expert centre. CONCLUSION: This consensus paper fills the gap between evidence-based medicine and daily clinical practice for the care of APS patients.

Fibrinogen Aalpha Thr312Ala polymorphism is associated with chronic thromboembolic pulmonary hypertension.

Although chronic thromboembolic pulmonary hypertension (CTEPH) is characterised by the persistence of organised thrombus, few pro-thrombotic risk factors have been identified in subjects with the disease. The aim of the present study was to compare the prevalence of eight functionally relevant haemostatic polymorphisms between CTEPH subjects and healthy controls. Genomic DNA was isolated from 214 CTEPH subjects and 200 healthy controls, and analysed for Factor V Leiden, prothrombin guanine (G) to adenine (A) substitution at nucleotide 20210 (20210G>A), plasminogen activator inhibitor-1 4G/5G, tissue plasminogen activator 7351 cytosine (C)>thymidine (T), Factor XIII 100G>T, fibrinogen Aalpha substitution of threonine with alanine at position 312 (Thr312Ala), fibrinogen Bbeta substitution of arginine with lysine at position 448 (Arg448Lys) and fibrinogen Bbeta 455G>A polymorphisms. A significant difference was demonstrated in fibrinogen Aalpha Thr312Ala genotype and allele frequencies between CTEPH subjects and controls. The presence of the alanine allele significantly increased the risk of CTEPH. The fibrinogen Aalpha alanine 312 allele alters fibrinogen alpha-alpha chain cross-linkage and has previously been associated with both increased risk of embolisation and increased resistance to thrombolysis. An association between this polymorphism and chronic thromboembolic pulmonary hypertension, therefore, supports an embolic aetiology for this disease, and may provide a mechanism by which thrombus persists following an acute event.

Correction of a dominant-negative von Willebrand factor multimerization defect by small interfering RNA-mediated allele-specific inhibition of mutant von Willebrand factor.

Essentials Substitution therapy for von Willebrand (VW) disease leaves mutant VW factor (VWF) unhindered. Presence of mutant VWF may negatively affect phenotypes despite treatment. Inhibition of VWF by allele-specific siRNAs targeting single-nucleotide polymorphisms is effective. Allele-specific inhibition of VWF p.Cys2773Ser improves multimerization. SUMMARY: Background Treatment of the bleeding disorder von Willebrand disease (VWD) focuses on increasing von Willebrand factor (VWF) levels by administration of desmopressin or VWF-containing concentrates. Both therapies leave the production of mutant VWF unhindered, which may have additional consequences, such as thrombocytopenia in patients with VWD type 2B, competition between mutant and normal VWF for platelet receptors, and the potential development of intestinal angiodysplasia. Most cases of VWD are caused by dominant-negative mutations in VWF, and we hypothesize that diminishing expression of mutant VWF positively affects VWD phenotypes. Objectives To investigate allele-specific inhibition of VWF by applying small interfering RNAs (siRNAs) targeting common single-nucleotide polymorphisms (SNPs) in VWF. This approach allows allele-specific knockdown irrespective of the mutations causing VWD. Methods Four SNPs with a high predicted heterozygosity within VWF were selected, and siRNAs were designed against both alleles of the four SNPs. siRNA efficiency, allele specificity and siRNA-mediated phenotypic improvements were determined in VWF-expressing HEK293 cells. Results Twelve siRNAs were able to efficiently inhibit single VWF alleles in HEK293 cells that stably produce VWF. Transient cotransfections of these siRNAs with two VWF alleles resulted in a clear preference for the targeted allele over the untargeted allele for 11 siRNAs. We also demonstrated siRNA-mediated phenotypic improvement of the VWF multimerization pattern of the VWD type 2A mutation VWF p.Cys2773Ser. Conclusions Allele-specific siRNAs are able to distinguish VWF alleles on the basis of one nucleotide variation, and are able to improve a severe multimerization defect caused by VWF p.Cys2773Ser. This holds promise for the therapeutic application of allele-specific siRNAs in dominant-negative VWD.