von Willebrand factor/ADAMTS-13 interactions at birth: implications for thrombosis in the neonatal period

Effect of In Vivo Administration of Fibrinogen Concentrate Versus Cryoprecipitate on Ex Vivo Clot Degradation in Neonates Undergoing Cardiac Surgery

BACKGROUND

Neonates undergoing cardiac surgery require fibrinogen replacement to restore hemostasis after cardiopulmonary bypass (CPB). Cryoprecipitate is often the first-line treatment, but recent studies demonstrate that fibrinogen concentrate (RiaSTAP; CSL Behring) may be acceptable in this population. This investigator-initiated, randomized trial compares cryoprecipitate to fibrinogen concentrate in neonates undergoing cardiac surgery (ClinicalTrials.gov NCT03932240). The primary end point was the percent change in ex vivo clot degradation from baseline at 24 hours after surgery between groups. Secondary outcomes included intraoperative blood transfusions, coagulation factor levels, and adverse events.

METHODS

Neonates were randomized to receive cryoprecipitate (control group) or fibrinogen concentrate (study group) as part of a post-CPB transfusion algorithm. Blood samples were drawn at 4 time points: presurgery (T1), after treatment (T2), arrival to the intensive care unit (ICU) (T3), and 24 hours postsurgery (T4). Using the mixed-effect models, we analyzed the percent change in ex vivo clot degradation from a patient's presurgery baseline at each time point. Intraoperative blood product transfusions, coagulation factor levels, perioperative laboratory values, and adverse events were collected.

RESULTS

Thirty-six neonates were enrolled (intent to treat [ITT]). Thirteen patients in the control group and seventeen patients in the study group completed the study per protocol (PP). After normalizing to the patient's own baseline (T1), no significant differences were observed in clot degradation at T2 or T3. At T4, patients in the study group had greater degradation when compared to those in the control group (826.5%, 95% confidence interval [CI], 291.1-1361.9 vs -545.9%, 95% CI, -1081.3 to -10.4; P < .001). Study group patients received significantly less median post-CPB transfusions than control group patients (ITT, 27.2 mL/kg [19.0-36.9] vs 41.6 [29.2-52.4]; P = .043; PP 26.7 mL/kg [18.8-32.2] vs 41.2 mL/kg [29.0-51.4]; P < .001). No differences were observed in bleeding or thrombotic events.

CONCLUSIONS

Neonates who received fibrinogen concentrate, as compared to cryoprecipitate, have similar perioperative ex vivo clot degradation with faster degradation at 24 hours postsurgery, less post-CPB blood transfusions, and no increased bleeding or thrombotic complications. Our findings suggest that fibrinogen concentrate adequately restores hemostasis and reduces transfusions in neonates after CPB without increased bleeding or thrombosis risk.

Psychological Burden Among Patients With Inherited Bleeding Disorders in Madinah Province, Saudi Arabia

Introduction Hereditary bleeding disorders, such as hemophilia and von Willebrand disease (VWD), result from specific deficiencies or malformations in the coagulation cascade proteins. These disorders can significantly impact both physical and psychological health. Complications such as depression, anxiety, and stress (DAS) can further exacerbate these impacts. Despite their significance, detailed prevalence data remain limited, especially for regions such as Madinah province in Saudi Arabia. This study aimed to determine the prevalence of DAS and their associated risk factors among patients with hereditary bleeding disorders in Madinah province, Saudi Arabia. Methods We conducted a cross-sectional study using telephonic interviews involving patients diagnosed with severe hemophilia A or B or VWD attending a hematology clinic in Madinah. Patients over 10 were included, and the study excluded those with central nervous system insults and platelet count concerns. The validated and reliable Depression Anxiety Stress Scale-21-item questionnaire and Statistical Product and Service Solutions (SPSS), version 26.0 (IBM SPSS Statistics for Windows, Armonk, NY), facilitated data collection and analysis, respectively. Results Of the 44 patients studied, 25% exhibited symptoms of depression, 45.5% showed signs of anxiety, and 29.5% had stress symptoms. Regarding symptom severity, 9.1% of patients experienced extremely severe depression, 15.9% had moderate anxiety, and 13.6% reported moderate stress. The prevalence of these psychological issues varied with patients' age and economic status. Notably, a significantly higher rate of depression was observed in patients over 15 years (42.9% vs. 8.7%; p=0.009). Additionally, while not statistically significant, patients with a high economic status reported increased rates of DAS. Conclusions Patients with inherited bleeding disorders, particularly those older than 15, manifest significant psychological distress. There is a pressing need for enhanced awareness, specialized screenings, and tailored counseling services to improve treatment adherence and overall quality of life. Given the findings, a comprehensive national study in Saudi Arabia is highly recommended, alongside the integration of specialized psychological services.

Mechanisms of ADAMTS13 regulation

Recombinant ADAMTS13 is currently undergoing clinical trials as a treatment for hereditary thrombotic thrombocytopenic purpura, a lethal microvascular condition resulting from ADAMTS13 deficiency. Preclinical studies have also demonstrated its efficacy in treating arterial thrombosis and inflammation without causing bleeding, suggesting that recombinant ADAMTS13 may have broad applicability as an antithrombotic agent. Despite this progress, we currently do not understand the mechanisms that regulate ADAMTS13 activity in vivo. ADAMTS13 evades canonical means of protease regulation because it is secreted as an active enzyme and has a long half-life in circulation, suggesting that it is not inhibited by natural protease inhibitors. Although shear can spatially and temporally activate von Willebrand factor to capture circulating platelets, it is also required for cleavage by ADAMTS13. Therefore, spatial and temporal regulation of ADAMTS13 activity may be required to stabilize von Willebrand factor-platelet strings at sites of vascular injury. This review outlines potential mechanisms that regulate ADAMTS13 in vivo including shear-dependency, local inactivation, and biochemical and structural regulation of substrate binding. Recently published structural data of ADAMTS13 is discussed, which may help to generate novel hypotheses for future research.

Relationship between Serum FGF21 and vWF Expression and Carotid Atherosclerosis in Elderly Patients with Hypertension

Cardiovascular (CV) and cerebrovascular (CBV) diseases are common in the elderly and cause severe damage, with high morbidity, disability, and mortality. Hypertension, as a risk factor for a variety of CV and CBV diseases, also affects many elderly patients. This study aimed to investigate the relationship between serum FGF21 and vWF expression and carotid atherosclerosis (CAS) in elderly patients with hypertension. We recruited 143 elderly hypertensive patients admitted to our hospital from July 2017 to November 2019 to this study, including 75 patients with comorbid CAS (the observation group, OG) and 68 patients without CAS (the control group, CG). Enzyme-linked immunosorbent assay (ELISA) was used to test serum expression levels of FGF21 and vWF; receiver operating characteristic (ROC) curves to evaluate the value of FGF21 and vWF in diagnosing CAS and predicting the 6-month prognosis in elderly hypertensive patients; Pearson's correlation analysis to analyze the correlation of FGF21/vWF with the plaque thickness and stenosis area in hypertensive patients with CAS. The incidence of CV and CBV events was markedly higher in the high FGF21/vWF group than in the low FGF21/vWF group. Patients from OG were divided into the high FGF21/vWF group and the low FGF21/vWF group based on the median expression level of FGF21/vWF, then the incidence of cardiovascular (CV) and cerebrovascular (CBV) events was compared between the high and low expression groups. Serum levels of FGF21 and vWF were markedly higher in patients from OG than in patients from CG. Both FGF21 and vWF were in positive correlation with the plaque thickness and stenosis area in patients from OG. The area under the ROC curve (AUC) for diagnosing CAS was 0.790 by FGF21 and 0.807 by vWF; the AUC for predicting the occurrence of CV and CBV events was 0.771 by FGF21 and 0.754 by vWF. Serum levels of FGF21 and vWF are increased in elderly patients with hypertension and comorbid CAS, so they can be used for diagnosing CAS and predicting prognosis.

An Optimized Purification Design for Extracting Active ADAMTS13 from Conditioned Media

ADAMTS13 is a hemostatic enzyme that breaks down pro-thrombotic ultra-large multimers of von Willebrand factor (VWF). The deficiency of ADAMTS13 increases VWF-mediated thrombogenic potential and may lead to thrombotic thrombocytopenic purpura (TTP). Recently, clinical studies have shown the development of acquired TTP after COVID-19 infection and a correlation between low ADAMTS13 plasma levels and increased mortality. As a result, investigating ADAMTS13 as a potential recombinant therapeutic is of broad interest in the field of hematology. ADAMTS13 is considered challenging to purify in its biologically active state. Current purification methods utilize immobilized metal ions, which can interfere with ADAMTS13 metalloprotease activity. For this reason, we optimized an alternative strategy to isolate milligram quantities of highly active recombinant ADAMTS13 (rADAMTS13) from conditioned media after exogenous expression in human cell line, HEK293. HEK293 cells stably expressing C-terminal V5-His-tagged ADAMTS13 were grown in two parallel systems, culture bottles and flasks, for identifying an optimal cultivation strategy. Subsequently, we employed anion exchange followed by anti-V5-tag affinity chromatography to purify rADAMTS13, and extracted rADAMTS13 of high specific activity while preserving its native post-translational modifications. In addition, this process has been optimized and scaled up to produce active rADAMTS13 at levels sufficient for laboratory-scale structural, enzymatic, and biochemical studies.

Contribution of the von Willebrand factor/ADAMTS13 imbalance to COVID-19 coagulopathy

The 2019 coronavirus disease (COVID-19) is the disease caused by SARS-CoV-2 infection. Although this infection has been shown to affect the respiratory system, a high incidence of thrombotic events has been observed in severe cases of COVID-19 and in a significant portion of COVID-19 nonsurvivors. Although prior literature has reported on both the coagulopathy and hypercoagulability of COVID-19, the specifics of coagulation have not been fully investigated. Observations of microthrombosis in patients with COVID-19 have brought attention to potential inflammatory endothelial injury. Von Willebrand factor (VWF) and its protease, A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), play an important homeostatic role in responding to endothelial injury. This report provides an overview of the literature investigating the role the VWF/ADAMTS13 axis may have in COVID-19 thrombotic events and suggests potential therapeutic strategies to prevent the progression of coagulopathy in patients with COVID-19.

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.

Neonatal thrombosis: risk factors and principles of prophylaxis

Data analysis on the pathogenesis and risk factors of neonatal thrombosis was carried out. The main risk factor of any neonatal thrombosis is central catheter installment, but other maternal, fetal and neonatal factors should be taken into consideration. We discuss the epidemiology of neonatal thrombosis and the main features of the hemostasis system in newborns, the most significant risk factors, including genetic and acquired thrombophilia. We consider the von Willebrand factor activity and ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) level in the development of neonatal thrombotic microangiopathy. Finally, we discuss the basic principles of prevented neonatal thrombosis by using low molecular weight heparins.

Coagulopathy and Thrombosis as a Result of Severe COVID-19 Infection: A Microvascular Focus

Coronavirus disease of 2019 (COVID-19) is the clinical manifestation of the respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While primarily recognized as a respiratory disease, it is clear that COVID-19 is systemic illness impacting multiple organ systems. One defining clinical feature of COVID-19 has been the high incidence of thrombotic events. The underlying processes and risk factors for the occurrence of thrombotic events in COVID-19 remain inadequately understood. While severe bacterial, viral, or fungal infections are well recognized to activate the coagulation system, COVID-19-associated coagulopathy is likely to have unique mechanistic features. Inflammatory-driven processes are likely primary drivers of coagulopathy in COVID-19, but the exact mechanisms linking inflammation to dysregulated hemostasis and thrombosis are yet to be delineated. Cumulative findings of microvascular thrombosis has raised question if the endothelium and microvasculature should be a point of investigative focus. von Willebrand factor (VWF) and its protease, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS-13), play important role in the maintenance of microvascular hemostasis. In inflammatory conditions, imbalanced VWF-ADAMTS-13 characterized by elevated VWF levels and inhibited and/or reduced activity of ADAMTS-13 has been reported. Also, an imbalance between ADAMTS-13 activity and VWF antigen is associated with organ dysfunction and death in patients with systemic inflammation. A thorough understanding of VWF-ADAMTS-13 interactions during early and advanced phases of COVID-19 could help better define the pathophysiology, guide thromboprophylaxis and treatment, and improve clinical prognosis.

A Single Synonymous Variant (c.354G>A [p.P118P]) in ADAMTS13 Confers Enhanced Specific Activity

Synonymous variants within coding regions may influence protein expression and function. We have previously reported increased protein expression levels ex vivo (~120% in comparison to wild-type) from a synonymous polymorphism variant, c.354G>A [p.P118P], of the ADAMTS13 gene, encoding a plasma protease responsible for von Willebrand Factor (VWF) degradation. In the current study, we investigated the potential mechanism(s) behind the increased protein expression levels from this variant and its effect on ADAMTS13 physico-chemical properties. Cell-free assays showed enhanced translation of the c.354G>A variant and the analysis of codon usage characteristics suggested that introduction of the frequently used codon/codon pair(s) may have been potentially responsible for this effect. Limited proteolysis, however, showed no substantial influence of altered translation on protein conformation. Analysis of post-translational modifications also showed no notable differences but identified three previously unreported glycosylation markers. Despite these similarities, p.P118P variant unexpectedly showed higher specific activity. Structural analysis using modeled interactions indicated that subtle conformational changes arising from altered translation kinetics could affect interactions between an exosite of ADAMTS13 and VWF resulting in altered specific activity. This report highlights how a single synonymous nucleotide variation can impact cellular expression and specific activity in the absence of measurable impact on protein structure.