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Patients with severe and sometimes moderate hemophilia B are prophylactically treated with factor IX concentrates to prevent bleeding. For some time now, various extended terminal half‐life (EHL) recombinant factor IX concentrates are available allowing less frequent administration during prophylaxis in comparison to standard half‐life recombinant FIX (rFIX). Especially, recombinant FIX‐Fc fusion protein (rFIXFc; Alprolix®) exhibits a rapid distribution phase, potentially due to binding to type IV collagen (Col4) in the extravascular space. Studies suggest that the presence of extravascular rFIXFc is protective against bleeding as without measurable FIX activity in plasma, and no extra bleeding seems to occur. The physiologically based pharmacokinetic (PBPK) model for rFIXFc which we describe in this study, is able to accurately predict the observed concentration‐time profiles of rFIXFc in plasma and is able to quantify the binding of rFIXFc to Col4 in the extravascular space after an intravenous dose of 50 IU/kg rFIXFc in a male population. Our model predicts that the total AUC of rFIXFc bound to Col4 in the extravascular space is approximately 19 times higher compared to the AUC of rFIXFc in plasma. This suggests that rFIXFc present in the extravascular compartment may play an important role in achieving hemostasis after rFIXFc administration. Further studies on extravascular distribution of rFIXFc and the distribution profile of other EHL‐FIX concentrates are needed to evaluate the predictions of our PBPK model and to investigate its clinical relevance. [ABSTRACT FROM AUTHOR]

Aims Although the risk of thrombosis is well documented for inflammatory bowel disease [IBD] patients, the underlying pathological mechanism seems to be different from other thrombotic conditions. Determining the factors responsible for the increased risk of thrombosis in IBD would help to improve the management of this frequent complication. Methods We studied the interplay between platelets, coagulation, and von Willebrand factor [VWF] in 193 IBD patients and in experimental models [acute and chronic] of colitis in wild-type and VWF-deficient mice. Results We found a platelet-dependent increase in thrombin generation in IBD patients and in our mouse model of colitis. Agglutinated platelets were present in the blood of patients and mice. Interestingly, we observed not only a significant increase in total VWF antigen, but we were also able to detect the presence of active VWF [VWF in its platelet-binding conformation; 3.2 ± 2.7 μg/mL] in the plasma of 30% of all IBD patients. In healthy controls, active VWF levels were <0.3 μg/mL. This led us to further explore experimental colitis in VWF-deficient mice and we observed that these mice were protected against the procoagulant state triggered by the colitis. Unexpectedly, these mice also showed a significant worsening of colitis severity in both acute and chronic models. Conclusion Platelets and VWF [including its active form] appear to be central players in the procoagulant phenotype in IBD. We observed that the role of VWF in haemostasis differs from its role in colonic tissue healing, potentially opening new therapeutic avenues for a life-threatening complication in IBD patients. [ABSTRACT FROM AUTHOR]

Aims Von Willebrand factor (VWF) is a plasma glycoprotein involved in primary haemostasis, while also having additional roles beyond haemostasis namely in cancer, inflammation, angiogenesis, and potentially in vascular smooth muscle cell (VSMC) proliferation. Here, we addressed how VWF modulates VSMC proliferation and investigated the underlying molecular pathways and the in vivo pathophysiological relevance. Methods and results VWF induced proliferation of human aortic VSMCs and also promoted VSMC migration. Treatment of cells with a siRNA against αv integrin or the RGT-peptide blocking αvβ3 signalling abolished proliferation. However, VWF did not bind to αvβ3 on VSMCs through its RGD-motif. Rather, we identified the VWF A2 domain as the region mediating binding to the cells. We hypothesized the involvement of a member of the LDL-related receptor protein (LRP) family due to their known ability to act as co-receptors. Using the universal LRP-inhibitor receptor-associated protein, we confirmed LRP-mediated VSMC proliferation. siRNA experiments and confocal fluorescence microscopy identified LRP4 as the VWF-counterreceptor on VSMCs. Also co-localization between αvβ3 and LRP4 was observed via proximity ligation analysis and immuno-precipitation experiments. The pathophysiological relevance of our data was supported by VWF-deficient mice having significantly reduced hyperplasia in carotid artery ligation and artery femoral denudation models. In wild-type mice, infiltration of VWF in intimal regions enriched in proliferating VSMCs was found. Interestingly, also analysis of human atherosclerotic lesions showed abundant VWF accumulation in VSMC-proliferating rich intimal areas. Conclusion VWF mediates VSMC proliferation through a mechanism involving A2 domain binding to the LRP4 receptor and integrin αvβ3 signalling. Our findings provide new insights into the mechanisms that drive physiological repair and pathological hyperplasia of the arterial vessel wall. In addition, the VWF/LRP4-axis may represent a novel therapeutic target to modulate VSMC proliferation. [ABSTRACT FROM AUTHOR]

We have developed and tested a novel microfluidic device for blood oxygenation, which exhibits a large surface area of gas exchange and can support long-term sustainable endothelialization of blood microcapillaries, enhancing its hemocompatibility for clinical applications. The architecture of the parallel stacking of the trilayers is based on a central injection for blood and a lateral injection/output for gas which allows significant reduction in shear stress, promoting sustainable endothelialization since cells can be maintained viable for up to 2 weeks after initial seeding in the blood microchannel network. The circular design of curved blood capillaries allows covering a maximal surface area at 4 inch wafer scale, producing high oxygen uptake and carbon dioxide release in each single unit. Since the conventional bonding process based on oxygen plasma cannot be used for surface areas larger than several cm2, a new "wet bonding" process based on soft microprinting has been developed and patented. Using this new protocol, each 4 inch trilayer unit can be sealed without a collapsed membrane even at reduced 15 μm thickness and can support a high blood flow rate. The height of the blood channels has been optimized to reduce pressure drop and enhance gas exchange at a high volumetric blood flow rate up to 15 ml min−1. The simplicity of connecting different units in the stacked architecture is demonstrated for 3- or 5-unit stacked devices that exhibit remarkable performance with low primary volume, high oxygen uptake and carbon dioxide release and high flow rate of up to 80 ml min−1. [ABSTRACT FROM AUTHOR]

Background: Angiodysplasia is a vascular malformation associated with gastrointestinal bleeding, generally observed in the elderly. This condition is unexpectedly more frequent in patients with von Willebrand disease (VWD)-type 2A having low levels of VWF high-molecular-weight-multimers (HMWMs) and increased VWF-degradation fragments (1). Aim: To develop an innovative murine model of VWD-type 2A and study the role of degraded-VWF in vascular processes. Methods: Mice expressing human (h) VWF, carrying the type 2A (p.R1597W) variant or wild-type (as control) and human GPIba, have been generated (hVWF(p.R1597W) + / +/hGP1BA + / + and hVWF + / +/hGP1BA + / +). Haemoglobin (Hb), VWF:Ag, propeptide, multimer pattern and factor VIII activity were analyzed. Tail-clip and tail-vein-transection (TVT) bleeding assays were assessed. Results: Control hVWF + / +/hGP1BA + / + -mice expressed 15 ± 4% VWF:Ag, 44 ± 8% FVIII activity and normal VWF multimers. hVWF(p. R1597W) + / +/hGP1BA + / + -mice are viable and do not display spontaneous bleeding manifestations. These mice expressed 3 ± 1% VWF:Ag and 7 ± 1% FVIII activity combined with an abnormal multimer pattern, with only low multimers and few degradation bands visible. Despite the relatively low VWF:Ag levels, hVWF + / +/hGP1BA + / + -mice displayed normal haemostatic responses in both the severe- (tail-clip) and milder- (TVT) bleeding assays. In contrast, hVWF(p.R1597W) + / + / hGP1BA + / + -mice had a severe bleeding phenotype. Interestingly, in the TVT model, although the amount of blood shed was consistent with severe bleeding, 57% of type 2A mice were capable of forming an occlusive, although unstable clot within 15 min of the injury, differing from the bleeding profile of VWF-deficient mice. Conclusion: We developed a unique humanized mouse models for VWD-type 2A. Experiments are ongoing to study the vasculature of these mice. [ABSTRACT FROM AUTHOR]

Concept Gene therapy with adeno-associated virus (AAV) vectors treats hemophilia A or B by delivering a functional F8 or F9 gene to hepatocytes. This single infusion enables endogenous production of FVIII or FIX protein, reducing bleeding in patients. Evolution Long-term clinical studies have provided insight into the efficacy, safety, and durability of AAV-mediated gene therapies for hemophilia A and B. Gene therapies have now been approved for hemophilia A (valoctocogene roxaparvovec) and hemophilia B (etranacogene dezaparvovec; fidanacogene elaparvovec) in select regions. Application The approved gene therapies are associated with a strong reduction in bleeding tendency and increased FVIII or FIX activity levels, without the need for additional FVIII or FIX replacement therapies, in the vast majority of patients. Future Steps Improvements in AAV technology, protein expression, and immunogenicity may render AAV-mediated gene therapies more efficient, longer lasting and safer for people with hemophilia A or B., (Copyright © 2024 American Society of Hematology.)

Over recent decades, management of people with hemophilia (PwH) has been greatly improved by scientific advances that have resulted in a rich and varied therapeutic landscape. Nevertheless, treatment limitations continue to drive innovation, and emerging options have the potential to realize further improvement. We advocate four general principles to optimize benefits from innovation: individualizing the treatment approach, targeting 'normal,' making the most of available resources, and considering treatment affordability. Ultimately, all PwH-men and women, of all ages and severities, and worldwide-should have access to treatment that fully prevents bleeding, while allowing personal, social, family, and professional lives of choice. Clearly, we are not there yet, but developing goals/milestones based on the principles we describe may help to achieve this., Competing Interests: The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: JB has received consultation and/or speaker’s fees from NovoNordisk, Roche, Sobi, Takeda, and CSL Behring. JA has received research grants from Sobi, CSL Behring, Takeda/Shire, and Bayer, and speaker’s fees and consultancy for Octapharma, Novo Nordisk, Pfizer, Bayer, Sobi, CSL Behring, Takeda/Shire, BioMarin, Uniqure, and Spark Therapeutics. CC has received payment or honoraria for lectures, presentations, speaker’s bureaus, manuscript writing, or educational events, and support for attending meetings and/or travel from Sobi, Bayer, Roche, and Novo Nordisk, and has also participated in data safety monitoring boards or advisory boards for Sobi, Bayer, Roche, and Novo Nordisk. GD has received consulting fees from Pfizer, Biomarin, CSL, Roche, and Sobi, and payment or honoraria for lectures, presentations, speaker’s bureaus, manuscript writing, or educational events from Pfizer, Spark Therapeutics, CSL, Bayer, Takeda, Roche, Chugai, and Sobi. KF has received unrestricted research grants from CSL Behring, Sobi, and Novo Nordisk, as well as consultancy fees from Hoffman-La Roche, Sanofi, Sobi, and Novo Nordisk, with all fees paid to her institution. CH has received research funding from Bayer, BioMarin, CSL Behring, Novo Nordisk, Pfizer, Shire/Takeda, and Sobi, as well as honoraria/speaker’s bureau fees from Bayer, CAF-DCF, CSL Behring, Hoffmann-La Roche, LFB, Novo Nordisk, Octapharma, Pfizer, Shire/Takeda, Sobi, and UniQure. KH has received grants for research or clinical studies (paid to her institution) from Bayer, CSL Behring, Novo Nordisk, Pfizer, Regeneron, Sanofi, and Sobi, as well honoraria or consultancy fees from Bayer, Biomarin, Biotest, CSL Behring, LFB, Novo Nordisk, Pfizer, Roche, Sobi, and Takeda. VJ-Y has received reimbursement for attending symposia/congresses and/or honoraria for speaking and/or honoraria for consulting, and/or funds for research from Takeda, Bayer, BioMarin, CSL Behring, Grifols, Novo Nordisk, Sobi, Roche, Octapharma, and Pfizer. RK has received consultancy fees and honoraria for lectures and advisory boards from Bayer, Biomarin, CSL Behring, Novo Nordisk, Grifols, Octapharma, Pfizer, Roche/Chugai, Sanofi, Sobi, and Takeda. ML has served on an advisory board for CSL Behring, as a consultant for Sobi, CSL Behring, Takeda, and Band Therapeutics, and has received research funding from Takeda and speaker fees from Sobi and Takeda. PJL has received research support to his institute from Sobi, Sanofi, BioMarin, and Roche. SL has acted as a paid consultant to Faust Pharmaceuticals Inc. MEM has acted as a paid speaker/consultant/advisor for Bayer, Biomarin, CSL Behring, Kedrion, LFB, Octapharma, Novo Nordisk, Pfizer, Roche, Sanofi, Sobi, and Takeda. JM has received honoraria and/or educational support from Sobi, Roche, Bayer, and CSL. JSO’D declares no conflicts of interest beyond the support for this manuscript from Sobi. CK has received funding from BFSH, Bayer, CSL Behring, Florio, MSD, Novo Nordisk, Roche/Chugai, Sobi/Sanofi, and Takeda for presentations and/or scientific advice, and his institution has received research funding from Bayer, Biotest, CSL Behring, Intersero, Novo Nordisk, Pfizer, Roche/Chugai, Sobi/Sanofi, and Takeda., (© The Author(s), 2024.)

von Willebrand disease (VWD) is the most common inherited bleeding disorder. The disorder is characterized by excessive mucocutaneous bleeding. The most common bleeding manifestations of this condition include nosebleeds, bruising, bleeding from minor wounds, menorrhagia or postpartum bleeding in women as well as bleeding after surgery. Other less frequent symptoms include gastrointestinal bleeding, haematomas or haemarthroses. VWD pathophysiology is complex and results from defects in von Willebrand factor (VWF) glycoprotein. Quantitative deficiencies are responsible for type 1 VWD with a partial decrease of VWF and type 3 with the complete absence of VWF. Qualitative abnormalities cause type 2 VWD, being further divided into types 2A, 2B, 2M and 2N. Although common, VWD is at risk of misdiagnosis, overdiagnosis and underdiagnosis owing to several factors, including complex diagnosis, variability of bleeding symptoms, presence of external variables (blood groups and other physiological modifiers such as exercise, thyroid hormones, oestrogens, and ageing), and lack of disease awareness among non-specialist health-care providers. Establishing the correct VWD diagnosis requires an array of specialized phenotypic assays and/or molecular genetic testing of the VWF gene. The management of bleeding includes increasing endogenous VWF levels with desmopressin or infusion of exogenous VWF concentrates (plasma-derived or recombinant). Fibrinolytic inhibitors, topical haemostatic agents and hormonal therapies are used as effective adjunctive measures., (© 2024. Springer Nature Limited.)

Recombinant factor VIII (rFVIII), rFVIIIFc and emicizumab are established treatment options in the management of hemophilia A. Each has its unique mode of action, which can influence thrombin generation kinetics and therefore also the kinetics of thrombin substrates. Such differences may potentially result in clots with different structural and physical properties. A starting observation of incomplete wound closure in a patient on emicizumab prophylaxis led us to employ a relevant mouse model in which we noticed that emicizumab-induced clots appeared less stable compared to FVIII-induced clots. We therefore analyzed fibrin formation in vitro and in vivo. In vitro fibrin formation was faster and more abundant in the presence of emicizumab than in the presence of rFVIII/rFVIIIFc. Furthermore, the time-interval between the initiation of fibrin formation and factor XIII activation was twice as long for emicizumab than as for rFVIII/rFVIIIFc. Scanning electron microscopy and immunofluorescent spinning-disk confocal microscopy of in vivo-generated clots confirmed increased fibrin formation in the presence of emicizumab. Unexpectedly, we also detected a different morphology between rFVIII/rFVIIIFcand emicizumab-induced clots. Contrary to the regular fibrin mesh obtained with rFVIII/rFVIIIFc, fibrin fibers appeared to be fused into large patches upon emicizumab treatment. Moreover, fewer red blood cells were detected in regions in which these fibrin patches were present. The presence of highly dense fibrin structures associated with a diffuse fiber structure in emicizumab-induced clots was also observed when using super-resolution imaging. We hypothesize that the modified kinetics of thrombin, fibrin and factor XIIIa generation contribute to differences in structural and physical properties between clots formed in the presence of FVIII or emicizumab.

People with nonsevere hemophilia (PWNSH) are phenotypically more diverse than those with severe hemophilia. Perceptions relating to a "nonsevere" phenotype have contributed to fewer research initiatives, fewer guidelines on optimal management, and a lack of standards for surveillance and clinical assessment for affected individuals. In many cases, episodes of abnormal bleeding could, if investigated, have led to earlier diagnosis. Furthermore, the major recent developments in therapy for hemophilia have largely focused on severe disease and, as a group, PWNSH have not been included in many key clinical trials. Benefiting people with severe disease, innovative replacement therapies have generally targeted factor levels that are above those present in a large proportion of PWNSH. Therapeutic advances can lead to improvement in phenotype for people with severe hemophilia over that currently experienced by many PWNSH. As a result, we are approaching a point where PWNSH may, in many countries, have a higher risk of bleeding and restriction in lifestyle than those with severe disease but with more limited therapeutic options. Given the multiple major advances in treatment for people with hemophilia, it is timely to review the aspects of nonsevere disease, to ensure equity in care and management for all individuals with this condition., Competing Interests: G.D. has received medical writing support for this manuscript from Sobi, consulting fees from Pfizer, BioMarin, CSL, Roche, and Sobi, and payment or honoraria for lectures, presentations, speaker's bureaus, manuscript writing, or educational events from Pfizer, Spark Therapeutics, CSL, Bayer, Takeda, Roche, Chugai, and Sobi.K.F. has received medical writing support for this manuscript from Sobi, grants from Novo Nordisk, CSL Behring, and Sobi, consulting fees from Roche and Sanofi, support for meeting attendance from Sobi, and has participated in data safety monitoring boards/advisory boards for Sanofi and Roche.P.J.L. has received medical writing support for this manuscript from Sobi, research grants to his institution from Pfizer, Roche, Sanofi, and Sobi, and participated in advisory board meetings for BioMarin, Sanofi, and Takeda.C.C. has received medical writing support for this manuscript from Sobi, as well as payment or honoraria for lectures, presentations, speaker's bureaus, manuscript writing, or educational events, and support for attending meetings and/or travel, from Sobi, Bayer, Roche, and Novo Nordisk. C.C. has also participated in data safety monitoring boards or advisory boards for Sobi, Bayer, Roche, and Novo Nordisk.M.L. has received medical writing support for this manuscript from Sobi, research funding from Takeda, consulting fees from Sobi, CSL Behring, Band Therapeutics, and Takeda, payment/honoraria from Takeda, Sobi, and Pfizer, support for meeting attendance from Takeda, and has roles in the WFH, EAHAD, FIGO, and ISTH., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).)

Aims: Von Willebrand factor (VWF) is a plasma glycoprotein involved in primary haemostasis, while also having additional roles beyond haemostasis namely in cancer, inflammation, angiogenesis, and potentially in vascular smooth muscle cell (VSMC) proliferation. Here, we addressed how VWF modulates VSMC proliferation and investigated the underlying molecular pathways and the in vivo pathophysiological relevance., Methods and Results: VWF induced proliferation of human aortic VSMCs and also promoted VSMC migration. Treatment of cells with a siRNA against αv integrin or the RGT-peptide blocking αvβ3 signalling abolished proliferation. However, VWF did not bind to αvβ3 on VSMCs through its RGD-motif. Rather, we identified the VWF A2 domain as the region mediating binding to the cells. We hypothesized the involvement of a member of the LDL-related receptor protein (LRP) family due to their known ability to act as co-receptors. Using the universal LRP-inhibitor receptor-associated protein, we confirmed LRP-mediated VSMC proliferation. siRNA experiments and confocal fluorescence microscopy identified LRP4 as the VWF-counterreceptor on VSMCs. Also co-localization between αvβ3 and LRP4 was observed via proximity ligation analysis and immuno-precipitation experiments. The pathophysiological relevance of our data was supported by VWF-deficient mice having significantly reduced hyperplasia in carotid artery ligation and artery femoral denudation models. In wild-type mice, infiltration of VWF in intimal regions enriched in proliferating VSMCs was found. Interestingly, also analysis of human atherosclerotic lesions showed abundant VWF accumulation in VSMC-proliferating rich intimal areas., Conclusion: VWF mediates VSMC proliferation through a mechanism involving A2 domain binding to the LRP4 receptor and integrin αvβ3 signalling. Our findings provide new insights into the mechanisms that drive physiological repair and pathological hyperplasia of the arterial vessel wall. In addition, the VWF/LRP4-axis may represent a novel therapeutic target to modulate VSMC proliferation., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2021. For permissions, please email: journals.permissions@oup.com.)