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100 years ago Dr. Eli Moschcowitz described the first case of thrombotic thrombocytopenic purpura. For many decades there were no recognized treatment options, and the mortality rate was extremely high. At the beginning of the 1990 s, therapy with steroids and plasma exchange became increasingly popular, although the mortality rate was still over 20 %. It took until the turn of the millennium for the disease mechanisms (ADAMTS13-deficiency) to be decoded in Bern and New York, thus paving the way for new therapy options. It has now become clear that acquired TTP (iTTP) is an autoimmune disease, and the autoantibodies are directed against ADAMTS13, a protease that cleaves large von-Willebrand multimers. This causes a severe ADAMTS13-deficiency. The ultralarge multimers persist and bind platelets, resulting in microvascular thrombosis. This is distinguished from congenital TTP (cTTP), in which severe ADAMTS13-deficiency is caused by mutations in the ADAMTS13-gene (Upshaw-Schulman syndrome). In other forms of thrombotic microangiopathy (TMA, e. g. aHUS), severe ADAMTS13-deficiency does not occur. Two randomized controlled studies demonstrated the benefit of the selective bivalent anti-von-Willebrand factor (vWF) nanobody Caplacizumab, approved in 2019, in the treatment of iTTP. Various publications from national iTTP cohorts improved the data and showed consistent reductions in the time until platelet normalization, a reduction in refractory courses and exacerbations (especially when therapy is controlled according to ADAMTS13-activity) as well as evidence of reduced mortality. Modern therapeutic options include strategies for preemptive therapy for ADAMTS13-relapse as well as plasma exchange-free treatment. The use of recombinant ADAMTS13 may also expand the therapeutic options in iTTP patients in the future., Competing Interests: Alle Autoren erhielten Honorare für Beratungstätigkeiten, u. a. für die Firma Sanofi. Des Weiteren sind RW, WM, MB, LV, MW, CvA und PB in die Entwicklung der deutschen AWMF-S3-Leitlinie TTP involviert., (Thieme. All rights reserved.)

Background and Aims: Heart failure (HF) is a leading cause of mortality worldwide and characterized by significant co-morbidities and dismal prognosis. Neutrophil extracellular traps (NETs) aggravate inflammation in various cardiovascular diseases; however, their function and mechanism of action in HF pathogenesis remain underexplored. This study aimed to investigate the involvement of a novel VWF-SLC44A2-NET axis in HF progression., Methods: NET levels were examined in patients with HF and mouse models of transverse aortic constriction (TAC) HF. PAD4 knockout mice and NET inhibitors (GSK-484, DNase I, NEi) were used to evaluate the role of NETs in HF. RNA sequencing was used to investigate the downstream mechanisms. Recombinant human ADAMTS13 (rhADAMTS13), ADAMTS13, and SLC44A2 knockouts were used to identify novel upstream factors of NETs., Results: Elevated NET levels were observed in patients with HF and TAC mouse models of HF. PAD4 knockout and NET inhibitors improved the cardiac function. Mechanistically, NETs induced mitochondrial dysfunction in cardiomyocytes, inhibiting mitochondrial biogenesis via the NE-TLR4-mediated suppression of PGC-1α. Furthermore, VWF/ADAMTS13 regulated NET formation via SLC44A2. Additionally, sacubitril/valsartan amplifies the cardioprotective effects of the VWF-SLC44A2-NET axis blockade., Conclusions: This study established the role of a novel VWF-SLC44A2-NET axis in regulating mitochondrial homeostasis and function, leading to cardiac apoptosis and contributing to HF pathogenesis. Targeting this axis may offer a potential therapeutic approach for HF treatment., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Abstract: Hereditary thrombotic thrombocytopenic purpura (hTTP) is a rare autosomal recessive, life-threatening disorder caused by a severe deficiency of the plasma enzyme, ADAMTS13. The current estimated prevalence of hTTP in different regions of the world, 0.5 to 2.0 patients per million, is determined by the frequency of diagnosed patients. To evaluate more accurately the worldwide prevalence of hTTP, and also the prevalence within distinct ethnic groups, we used data available in exome and genome sequencing of 807 162 (730 947 exomes, 76 215 genomes) subjects reported recently by the Genome Aggregation Database (gnomAD-v4.1). Among 1 614 324 analyzed alleles in the gnomAD population we identified 6321 distinct ADAMTS13 variants. Of these, 758 were defined as pathogenic; 140 (18%) variants had been previously reported and 618 (82%) were novel (predicted as pathogenic). In total 10 154 alleles (0.6%) were carrying the reported or predicted pathogenic variants; 7759 (77%) with previously reported variants. Considering all 758 pathogenic variants and also only the 140 previously reported variants, we estimated a global hTTP prevalence of 40 and 23 cases per 106, respectively. Considering only the 140 previously reported variants, the highest estimated prevalence was in East Asians (42 per 106). The estimated prevalences of other populations were: Finnish, 32 per 106; non-Finnish Europeans, 28 per 106; Admixed Americans, 19 per 106; Africans/African Americans, 6 per 106; and South Asians, 4 per 106. The lowest prevalences were Middle Eastern, 1 per 106 and Ashkenazi Jews, 0.7 per 106. This population-based genetic epidemiology study reports that hTTP prevalence is substantially higher than the currently estimated prevalence based on diagnosed patients. Many patients with hTTP may not be diagnosed or may have died during the neonatal period., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Introduction: Hereditary thrombotic thrombocytopenic purpura (hTTP) is caused by deficiency of plasma ADAMTS13 activity, resulting from ADAMTS13 mutations. ADAMTS13 cleaves ultra large von Willebrand factor (VWF), thus reducing its multimer sizes. Hereditary deficiency of plasma ADAMTS13 activity leads to the formation of excessive platelet-VWF aggregates in small arterioles and capillaries, resulting in hTTP., Areas Covered: PubMed search from 1956 to 2024 using thrombotic thrombocytopenic purpura and therapy identified 3,675 articles. Only the articles relevant to the topic were selected for discussion, which focuses on pathophysiology, clinical presentations, and mechanisms of action of emerging therapeutics for hTTP. Current therapies include infusion of plasma, or coagulation factor VIII, or recombinant ADAMTS13. Emerging therapies include anti-VWF A1 aptamers or nanobody and gene therapies with adeno-associated viral vector or self-inactivated lentiviral vector or a sleeping beauty transposon system for a long-term expression of a functional ADAMTS13 enzyme., Expert Opinion: Frequent plasma infusion remains to be the standard of care in most parts of the world, while recombinant ADAMTS13 has become the treatment of choice for hTTP in some of the Western countries. The success of gene therapies in preclinical models may hold a promise for future development of these novel approaches for a cure of hTTP.

Background: Thrombotic microangiopathy (TMA) is associated with carfilzomib, and knowledge of carfilzomib-induced TMA is based mainly on case reports. This study investigated the clinical characteristics of patients with carfilzomib-induced TMA and provided a reference for the rational use of carfilzomib., Methods: Reports of carfilzomib-induced TMA were collected for retrospective analysis by searching the Chinese and English databases from inception to January 31, 2024., Results: Sixty-six patients were included, with a median age of 63 years (range 39, 85). The median time to onset of TMA was 42 days (range 1, 1825) from initial administration, and the median number of cycles was 3 cycles (range 1, 15). Hemolytic anemia was recorded in 64 patients, with a median of 8.3 g/dL (range 4.6, 13). Sixty-three patients had thrombocytopenia with a median of 18 × 10 9 /L (range 1, 139). The median value of increased LDH was 1192 IU/L (range 141, 5378). ADAMTS13 activity was normal in 41 (62.1 %) of the 42 patients. Mutations were found in 9 (13.6 %) of the 15 patients. Fifty-seven patients achieved a clinical response after discontinuing carfilzomib and receiving therapeutic plasma exchange (53.0 %), eculizumab (24.2 %), or hemodialysis (39.4 %)., Conclusion: Carfilzomib-induced TMA is an important adverse event that should be considered in patients receiving carfilzomib for multiple myeloma with anemia, thrombocytopenia, and acute kidney injury. Withdrawal of carfilzomib and treatment with eculizumab have proven successful in some patients., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

We present a case of a child with congenital thrombotic thrombocytopenic purpura found to have a compound heterozygous variant in the ADAMTS13 gene with a novel variant resulting in a large duplication of exons 9-11 of ADAMTS13 This variant was identified through additional molecular testing via a chromosomal microarray analysis. To our knowledge, this assay had not previously been utilised to identify an ADAMTS13 variant and the additional testing was possible through the involvement of a genetic counsellor., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Exposure to chronic psychological stress (CPS) is a risk factor for thrombotic cardiocerebrovascular diseases (CCVDs). The expression and activity of the cysteine cathepsin K (CTSK) are upregulated in stressed cardiovascular tissues, and we investigated whether CTSK is involved in chronic stress-related thrombosis, focusing on stress serum-induced endothelial apoptosis., Methods and Results: Eight-week-old wild-type male mice (CTSK +/+ ) randomly divided to non-stress and 3-week restraint stress groups received a left carotid artery iron chloride3 (FeCl 3 )-induced thrombosis injury for biological and morphological evaluations at specific timepoints. On day 21 post-stress/injury, the stress had enhanced the arterial thrombi weights and lengths, in addition to harmful alterations of plasma ADAMTS13, von Willebrand factor, and plasminogen activation inhibitor-1, plus injured-artery endothelial loss and CTSK protein/mRNA expression. The stressed CTSK +/+ mice had increased levels of injured arterial cleaved Notch1, Hes1, cleaved caspase8, matrix metalloproteinase-9/-2, angiotensin type 1 receptor, galactin3, p16 IN4A , p22phox, gp91 phox , intracellular adhesion molecule-1, TNF-α, MCP-1, and TLR-4 proteins and/or genes. Pharmacological and genetic inhibitions of CTSK ameliorated the stress-induced thrombus formation and the observed molecular and morphological changes. In cultured HUVECs, CTSK overexpression and silencing respectively increased and mitigated stressed-serum- and H 2 O 2 -induced apoptosis associated with apoptosis-related protein changes. Recombinant human CTSK degraded γ-secretase substrate in a dose-dependent manor and activated Notch1 and Hes1 expression upregulation., Conclusions: CTSK appeared to contribute to stress-related thrombosis in mice subjected to FeCl 3 stress, possibly via the modulation of vascular inflammation, oxidative production and apoptosis, suggesting that CTSK could be an effective therapeutic target for CPS-related thrombotic events in patients with CCVDs., (© 2024. The Author(s).)

Background: Congenital thrombotic thrombocytopenic purpura (TTP) results from severe hereditary deficiency of ADAMTS13. The efficacy and safety of recombinant ADAMTS13 and standard therapy (plasma-derived products) administered as routine prophylaxis or on-demand treatment in patients with congenital TTP is not known., Methods: In this phase 3, open-label, crossover trial, we randomly assigned patients in a 1:1 ratio to two 6-month periods of prophylaxis with recombinant ADAMTS13 (40 IU per kilogram of body weight, administered intravenously) or standard therapy, followed by the alternate treatment; thereafter, all the patients received recombinant ADAMTS13 for an additional 6 months. The trigger for this interim analysis was trial completion by at least 30 patients. The primary outcome was acute TTP events. Manifestations of TTP, safety, and pharmacokinetics were assessed. Patients who had an acute TTP event could receive on-demand treatment., Results: A total of 48 patients underwent randomization; 32 completed the trial. No acute TTP event occurred during prophylaxis with recombinant ADAMTS13, whereas 1 patient had an acute TTP event during prophylaxis with standard therapy (mean annualized event rate, 0.05). Thrombocytopenia was the most frequent TTP manifestation (annualized event rate, 0.74 with recombinant ADAMTS13 and 1.73 with standard therapy). Adverse events occurred in 71% of the patients with recombinant ADAMTS13 and in 84% with standard therapy. Adverse events that were considered by investigators to be related to the trial drug occurred in 9% of the patients with recombinant ADAMTS13 and in 48% with standard therapy. Trial-drug interruption or discontinuation due to adverse events occurred in no patients with recombinant ADAMTS13 and in 8 patients with standard therapy. No neutralizing antibodies developed during recombinant ADAMTS13 treatment. The mean maximum ADAMTS13 activity after recombinant ADAMTS13 treatment was 101%, as compared with 19% after standard therapy., Conclusions: During prophylaxis with recombinant ADAMTS13 in patients with congenital TTP, ADAMTS13 activity reached approximately 100% of normal levels, adverse events were generally mild or moderate in severity, and TTP events and manifestations were rare. (Funded by Takeda Development Center Americas and Baxalta Innovations; ClinicalTrials.gov number, NCT03393975.)., (Copyright © 2024 Massachusetts Medical Society.)

Background: Fibrin, von Willebrand factor, and extracellular DNA from neutrophil extracellular traps all contribute to acute ischemic stroke thrombus integrity., Objectives: In this study, we explored how the proteomic composition of retrieved thromboemboli relates to susceptibility to lysis with distinct thrombolytics., Methods: Twenty-six retrieved stroke thromboemboli were portioned into 4 segments, with each subjected to 1 hour of in vitro lysis at 37 °C in 1 of 4 solutions: tissue plasminogen activator (tPA), tPA + von Willebrand factor-cleaving ADAMTS-13, tPA + DNA-cleaving deoxyribonuclease (DNase) I, and all 3 enzymes. Lysis, characterized by the percent change in prelysis and postlysis weight, was compared across the solutions and related to the corresponding abundance of proteins identified on mass spectrometry for each of the thromboemboli used in lysis., Results: Solutions containing DNase resulted in approximately 3-fold greater thrombolysis than that with the standard-of-care tPA solution (post hoc Tukey, P < .01 for all). DNA content was directly related to lysis in solutions containing DNase (Spearman's ρ > 0.39 and P < .05 for all significant histones) and inversely related to lysis in solutions without DNase (Spearman's ρ < -0.40 and P < .05 for all significant histones). Functional analysis suggests distinct pathways associated with susceptibility to thrombolysis with tPA (platelet-mediated) or DNase (innate immune system-mediated)., Conclusion: This study demonstrates synergy of DNase and tPA in thrombolysis of stroke emboli and points to DNase as a potential adjunct to our currently limited selection of thrombolytics in treating acute ischemic stroke., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Hereditary TTP (hTTP), termed Upshaw-Schulman syndrome, is an ultra-rare disorder caused by a severe deficiency of plasma ADAMTS13 activity that allows circulation of ultra-large von Willebrand factor (UL-VWF) multimers. The greatest risk for hTTP is in their first days after birth, when 35-50% of patients will have severe hemolysis, jaundice, and thrombocytopenia. It is often fatal without effective treatment. In utero, fetal blood flowing from the pulmonary artery through the ductus arteriosus (DA) to the aorta is under low-shear-force. At birth, blood flow through the DA reverses to a left-to-right shunt, and the diameter of the DA begins to decrease due to hyper-oxygenated blood and decreased plasma prostaglandin E 2 . This causes turbulent circulation that unfolds UL-VWF, allowing platelet aggregation. If the DA closes promptly, hTTP newborns survive, but if it remains patent, turbulent circulation persists, triggering microvascular thrombosis. hTTP is commonly diagnosed as hemolytic disease of the fetus and newborn (HDFN) caused by anti-red cell antibodies and treated with exchange blood transfusion, which prevents kernicterus even when the diagnosis of hTTP is missed. The diagnosis of newborn-onset hTTP should be considered because HDFN does not cause severe thrombocytopenia, which might be effectively treated with recombinant ADAMTS13., (© 2024. Japanese Society of Hematology.)

Objective: Non-cirrhotic intrahepatic portal hypertension (NCIPH), a portal microangiopathy affecting small portal vein radicles, is a disease of Indian sub-continent. NCIPH appears to be a complex disease with interactions between inherited and acquired factors, though the exact pathophysiological mechanism is unknown. We aimed at investigating the genetic variants that might contribute to susceptibility to NCIPH., Methods: In this case-control study, we analyzed genes associated with microangiopathy-VWF-ADAMTS13 (von Willebrand factor and its cleavase enzyme - a disintegrin and matrix metalloprotease with thrombospondin type-1 motifs member 13) and alternative complement system vitamin B 12 metabolism and with familial NCIPH., Result: Eighty-four Indian patients with liver biopsy-proven NCIPH (cases) and 103 healthy controls (matched for residential region of India) were included in the study. Targeted next-generation sequencing (NGS) panel, comprising 11 genes of interest, was done on 54 cases. Genotyping of selected variants was performed in 84 cases and 103 healthy controls. We identified variants in MBL2, CD46 and VWF genes either associated or predisposing to NCIPH. We also identified a single case with a novel compound heterozygous mutation in MBL2 gene, possibly contributing to development of NCIPH., Conclusion: In this first of a kind comprehensive gene panel study, multiple variants of significance have been noted, especially in ADAMTS13-VWF and complement pathways in NCIPH patients in India. Functional significance of these variants needs to be further studied., (© 2023. Indian Society of Gastroenterology.)

Abstract: Although it is caused by a single-nucleotide mutation in the β-globin gene, sickle cell anemia (SCA) is a systemic disease with complex, incompletely elucidated pathologies. The mononuclear phagocyte system plays critical roles in SCA pathophysiology. However, how heterogeneous populations of hepatic macrophages contribute to SCA remains unclear. Using a combination of single-cell RNA sequencing and spatial transcriptomics via multiplexed error-robust fluorescence in situ hybridization, we identified distinct macrophage populations with diversified origins and biological functions in SCA mouse liver. We previously found that administering the von Willebrand factor (VWF)-cleaving protease ADAMTS13 alleviated vaso-occlusive episode in mice with SCA. Here, we discovered that the ADAMTS13-cleaved VWF was cleared from the circulation by a Clec4f+Marcohigh macrophage subset in a desialylation-dependent manner in the liver. In addition, sickle erythrocytes were phagocytized predominantly by Clec4f+Marcohigh macrophages. Depletion of macrophages not only abolished the protective effect of ADAMTS13 but exacerbated vaso-occlusive episode in mice with SCA. Furthermore, promoting macrophage-mediated VWF clearance reduced vaso-occlusion in SCA mice. Our study demonstrates that hepatic macrophages are important in the pathogenesis of SCA, and efficient clearance of VWF by hepatic macrophages is critical for the protective effect of ADAMTS13 in SCA mice., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

A 27-year-old woman was diagnosed with idiopathic thrombocytopenic purpura in the neonatal period, and was admitted to our hospital after presenting with impaired consciousness, purpura, nausea and vomiting, with a platelet count of 10×10 9 /l. Congenital thrombotic thrombocytopenic purpura (cTTP) was suspected on the basis of recurrent thrombocytopenia and impaired consciousness, so tests for ADAMTS13 activity and inhibitor were performed. ADAMTS13 activity was severely decreased, ADAMTS13 inhibitor was negative, and platelet count increased after transfusion of fresh frozen plasma. These findings and the results of genetic testing done on all family members led to a diagnosis of cTTP. cTTP requires differential diagnosis even in adults. If a patient diagnosed with ITP in childhood has a history or findings that suggest cTTP during follow-up observation, it is necessary to actively consider ADAMTS13 testing.

Thrombophilia in venous thromboembolism (VTE) is multifactorial. Von Willebrand factor (vWF) plays a major role in primary hemostasis. While elevated vWF levels are well documented in VTE, findings related to its cleaving protease (ADAMTS-13) are contradicting. The aim of this study was to determine vWF, ADAMTS-13, and the multifactorial Thrombospondin-1 (TSP-1) protein levels in patients after 3-6 months following an unprovoked VTE episode. We also explored a possible association with factor V Leiden (FVL) mutation. vWF, ADAMTS-13 and TSP-1 were analyzed using ELISA kits in 60 VTE patients and 60 controls. Patients had higher levels of vWF antigen ( P  = .021), vWF collagen-binding activity ( P  = .008), and TSP-1 protein ( P  < .001) compared to controls. ADAMTS-13 antigen was lower in patients ( P  = .046) compared to controls but ADAMTS-13 activity was comparable between the two groups ( P  = .172). TSP-1 showed positive correlation with vWF antigen (rho = 0.303, P  = .021) and negative correlation with ADAMTS-13 activity (rho = -0.244, P  = .033) and ADAMTS-13 activity/vWF antigen ratio (rho = -0.348, P  = .007). A significant association was found between the presence of FVL mutation and VTE (odds ratio (OR): 9.672 (95% confidence interval (CI) 2.074-45.091- P  = .004), but no association was found between the mutation and the studied proteins ( P  > .05). There appears to be an imbalance between vWF and ADAMTS-13 in VTE patients even after 3-6 months following the onset of VTE. We report that the odds of developing VTE in carriers of FVL mutation are 9.672 times those without the mutation, but the presence of this mutation is not associated with the studied proteins., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

ADAMTS13 is a plasma metalloprotease with the primary function of cleaving VWF to maintain hemostasis. Circulating ADAMTS13 is in the closed conformation until blood vessel injury triggers a VWF-dependant activation to the open active form of the protein. ADAMTS13 is a multi-domain protein with the domains broadly functioning to interact and cleave VWF or maintain global latency of ADAMTS13. Thrombotic Thrombocytopenic Purpura is a disease characterized by excessive thrombi formation in the microvasculature, diagnosis is made when ADAMTS13 activity is <10%. In the hereditary form, a variety of mutations are found throughout all domains of ADAMTS13, examples are given alongside details of each domain in this article. ADAMTS13 mutations can inhibit the binding and cleavage of VWF directly or indirectly through reduced secretion, leading to increased size of VWF multimers and platelet recruitment. Molecular characterization of ADAMTS13 may provide insight into the mechanisms of TTP to aid in both scientific and clinical research.

The relationship between von Willebrand factor (VWF) and inflammation has attracted considerable attention in recent years. VWF, which is stored in the Weibel-Palade bodies (WPBs) of endothelial cells (ECs), is released from WPBs in response to inflammatory stimuli and is thought to contribute to inflammation by promoting leukocyte extravasation. In this study, lung injury model mice were produced by intratracheal injection with lipopolysaccharides. The severity of lung inflammation was evaluated in mice with different genotypes (wild-type, Vwf -/- , Adamts13 -/- ) and mice treated with drugs that inhibit VWF function. Lung inflammation was significantly ameliorated in Vwf -/- mice compared with wild-type mice. Furthermore, inflammation was significantly suppressed in wild-type mice treated with anti-VWF A1 antibody or recombinant human ADAMTS13 compared with the untreated control group. The underlying mechanism appears to be an increased VWF/ADAMTS13 ratio at the site of inflammation and the interaction between blood cell components, such as leukocytes and platelets, and the VWF A1 domain, which promotes leukocyte infiltration into the lung. This study suggested that ADAMTS13 protein and other VWF-targeting agents may be a novel therapeutic option for treatment of pulmonary inflammatory diseases., (© 2023. Japanese Society of Hematology.)

Congenital thrombotic thrombocytopenic purpura (TTP) is a rare autosomal recessive genetic disorder caused by mutations in the ADAMTS13 gene. Approximately 200 mutations of the ADAMTS-13 gene have been identified, although only a few have been characterized through in vitro expression studies. We conducted an investigation on a male congenital TTP patient with reduced plasma levels of ADAMTS13 activity. DNA sequence analysis revealed two mutations on chromosome 9 ( 1.9q34.2 ) in the patient's ADAMTS13 gene. One mutation was a non-synonymous mutation ( exon 5: c.A530G: p.Y177C ), while the other was a nonsense mutation ( exon 21: c.G2651A: p.W884X ). Both mutations were found to be heterozygous. The patient's parents had no history of thrombocytopenia or neurological symptoms. DNA sequence analysis showed the patient's father was a heterozygote for the nonsense mutation of the ADAMTS13 gene ( exon 21: c.G2651A: p.W884X ), while the mother was a heterozygote for the non-synonymous mutation of the ADAMTS13 gene (exon 5: c.A530G: p.Y177C ). To investigate the mechanism behind ADAMTS13 deficiency in this patient, wild type (WT), ADAMTS13 p.Y177C , and ADAMTS13 p.W884X were transiently expressed in 293-6E cells. Expression studies revealed a significant reduction in enzyme activity and secretion, although the protease was detected within the cells. The 3D structures of the natural and mutated ADAMTS-13 proteins were partially reconstructed using the Phyre2 web server. The mutation that replaces the tyrosine residue at amino acid position 177 with cysteine may result in decreased steric hindrance and a looser structure. This mutation affects the binding of calcium ions and the secretion of the enzyme from intracellular to extracellular compartments.

Background: The association between acquired ADAMTS13-deficient thrombotic thrombocytopenic purpura (aTTP) and systemic lupus erythematosus (SLE) has been studied; however, the underlying molecular causes remain poorly understood. This research aimed to employ bioinformatics approaches to elucidate potential molecular mechanisms contributing to the pathogenesis of SLE and aTTP., Material and Methods: The Gene Expression Omnibus (GEO) database yielded GSE121239 and GSE36418 to get mutual different expression genes (DEGs). Subsequently, DEGs were subjected to process Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Then, the DEGs were used for protein-protein interaction (PPI) analysis and screened for hub genes and drugs by the DGIDB drug database., Results: A total of 87 DEGs between the SLE and TTP datasets were identified. In the GO and KEGG analyses, DEGs were mainly enriched in the "regulation of transcription by RNA polymerase II" and "signaling pathways regulating pluripotency of stem cells." After a PPI analysis, three hub genes (BMPR2, SMAD5, and ATF2) were identified. Finally, two drugs targeted to ATF2 were predicted by the DGIDB drug database., Conclusions: Three core genes were linked to the molecular pathogenesis of SLE and aTTP, and two drugs may be viable treatments for both diseases., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: Thrombotic thrombocytopenic purpura (TTP) is a rare and fatal disease caused by a severe deficiency in the metalloprotease ADAMTS13 and is characterized by thrombotic microangiopathy. The present study aimed to investigate the genes and variants associated with TTP in a Chinese population., Methods: Target sequencing was performed on 220 genes related to complements, coagulation factors, platelets, fibrinolytic, endothelial, inflammatory, and anticoagulation systems in 207 TTP patients and 574 controls. Subsequently, logistic regression analysis was carried out to identify the TTP-associated genes based on the counts of rare deleterious variants in the region of a certain gene. Moreover, the associations between common variants and TTP were also investigated., Results: ADAMTS13 was the only TTP-associated gene (OR = 3.77; 95% CI: 1.82-7.81; P=3.6×10 ȡ4 ) containing rare deleterious variants in TTP patients. Among these 8 variants, 5 novel rare variants that might contribute to TTP were identified, including rs200594025, rs782492477, c.T1928G (p.I643S), c.3336&#95;3361del (p.Q1114Afs*20), and c.3469&#95;3470del (p.A1158Sfs*17). No common variants associated with TTP were identified under the stringent criteria of correction for multiple testing., Conclusion: ADAMTS13 is the primary gene related to TTP. The genetic variants associated with the occurrence of TTP were slightly different between the Chinese and European populations., (© 2023. Huazhong University of Science and Technology.)

Background: ADAMTS13 is a circulating metalloprotease that cleaves von Willebrand factor (VWF) in a shear-dependent manner. ADAMTS13 is secreted as an active protease but has a long half-life, suggesting that it is resistant to circulating protease inhibitors. These zymogen-like properties indicate that ADAMTS13 exists as a latent protease that is activated by its substrate., Objectives: To investigate the mechanism of ADAMTS13 latency and resistance to metalloprotease inhibitors., Methods: Probe the active site of ADAMTS13 and variants using alpha-2 macroglobulin (A2M), tissue inhibitors of metalloproteases (TIMPs), and Marimastat., Results: ADAMTS13 and C-terminal deletion mutants are not inhibited by A2M, TIMPs, or Marimastat, but cleave FRETS-VWF73, suggesting that the metalloprotease domain is latent in the absence of substrate. Within the metalloprotease domain, mutating the gatekeeper triad (R193, D217, D252) or substituting the calcium-binding (R180-R193) or the variable (G236-S263) loops with corresponding features from ADAMTS5 did not sensitize MDTCS to inhibition. However, substituting the calcium-binding loop and an extended variable loop (G236-S263) corresponding to the S1-S1' pockets with those from ADAMTS5, resulted in MDTCS-GVC5 inhibition by Marimastat, but not by A2M or TIMP3. Substituting the MD domains of ADAMTS5 into full-length ADAMTS13 resulted in a 50-fold reduction in activity compared with the substitution into MDTCS. However, both chimeras were susceptible to inhibition, suggesting that the closed conformation does not contribute to the latency of the metalloprotease domain., Conclusion: The metalloprotease domain protects ADAMTS13 from inhibitors and exists in a latent state that is partially maintained by loops flanking the S1 and S1' specificity pockets., (Copyright © 2023 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Background: Hereditary thrombotic thrombocytopenic purpura (hTTP) is associated with severe obstetric morbidity (SOM) during pregnancy. Treatment with fresh frozen plasma (FFP) mitigates the risk in some women, but others respond poorly and continue to suffer obstetric complications., Objectives: To determine a possible association between SOM and elevated nonpregnant von Willebrand factor (NPVWF) antigen levels in women with hTTP and whether the latter can predict the response to FFP transfusion., Methods: This was a cohort-based study of women with hTTP due to homozygous c.3772delA mutation of ADAMTS-13 who had pregnancies both with and without FFP treatment. Occurrences of SOM were determined from medical records. Generalized estimated equation logistic regressions and receiver operating characteristic curve analysis determined the NPVWF antigen levels associated with the development of SOM., Results: Fourteen women with hTTP had 71 pregnancies; of which 17 (24%) culminated in pregnancy loss and 32 (45%) were complicated by SOM. FFP transfusions were administered in 32 (45%) of the pregnancies. Treated women had decreased SOM (28% vs 72%, p < .001) and preterm thrombotic thrombocytopenic purpura exacerbations (18% vs 82%, p < .001) and higher median NPVWF antigen levels than those of women with uncomplicated pregnancies (p = .018). Among the treated women, median NPVWF antigen levels were higher in those with SOM than in those without SOM (225% vs 165%, p = .047). Logistic regression models demonstrated a significant 2-way association between elevated NPVWF antigen levels (for SOM, odds ratio, 1.08; 95% CI, 1.001-1.165; p = .046) and SOM (for elevated NPVWF antigen levels, odds ratio, 1.6; 95% CI, 1.329-1.925; p < .001). The receiver operating characteristic curve analysis demonstrated that an NPVWF antigen level of 195% had 75% sensitivity and 72% specificity for SOM., Conclusion: Elevated NPVWF antigen levels are associated with SOM in women with hTTP. Women with levels >195% may benefit from increased surveillance and more intensive FFP treatment during pregnancy., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2023 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Background: In reperfused myocardial infarction, VWF (von Willebrand factor)-mediated platelet adhesion contributes to impaired microvascular reflow and possibly also to postmyocardial infarction inflammation. We hypothesized that postischemic thromboinflammatory processes are worsened by elevated LDL (low-density lipoprotein) cholesterol., Methods: Myocardial ischemia-reperfusion or sham procedure was performed in wild-type mice and hyperlipidemic mice deficient for the LDL receptor and Apobec-1 (apolipoprotein-B mRNA editing enzyme catalytic polypeptide-1; DKO [double knockout]). DKO subgroups were treated with N-acetylcysteine, which inhibits pro-adhesive VWF multimers or with recombinant ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motifs-13), which enzymatically cleaves endothelial surface-associated VWF. Myocardial contrast echocardiography perfusion imaging and molecular imaging for VWF, platelet glycoprotein Ibα, and leukocyte CD18 (cluster of differentiation) were performed 30 minutes post-reperfusion. Histology, infarct sizing, and echocardiography were performed at 1.5 or 72 hours; late echocardiography was performed at day 21., Results: After ischemia-reperfusion, DKO compared with wild-type mice had ≈2-fold higher ( P <0.05) risk area signal for microvascular platelet adhesion, VWF, and CD18; greater impairment in microvascular reflow, and 2-fold larger infarct size. Treatment of DKO mice with N-acetylcysteine and ADAMTS13 reduced molecular imaging signal for microvascular platelet adhesion, VWF, and CD18; improved early microvascular reflow; and reduced eventual infarct size. ADAMTS13 suppressed the postmyocardial infarction neutrophil and monocyte infiltration, enhanced the time-dependent recovery of left ventricular systolic function, and prevented late left ventricular remodeling., Conclusions: In reperfused myocardial infarction, elevated LDL cholesterol promotes thromboinflammation through excess microvascular endothelial VWF and platelet adhesion, resulting in less microvascular reflow and larger infarct size. In the presence of elevated LDL cholesterol, therapies that suppress endothelial-associated VWF can promote recovery of left ventricular function and protect against remodeling., Competing Interests: Disclosures None.

Purpose of Review: This review provides an update on the pathophysiology of sickle cell disease (SCD) with a particular focus on the dysregulation of the von Willebrand factor (VWF) - ADAMTS13 axis that contributes to its pathogenesis. In discussing recent developments, we hope to encourage new and ongoing discussions surrounding therapeutic targets for SCD., Recent Findings: Within the last 5 years, the role of VWF in the pathophysiology of SCD has been further elucidated and is now a target of study in ongoing clinical trials., Summary: The pathophysiology of SCD is multifaceted, as it involves systemwide vascular activation, altered blood rheology, and the activation of immune responses and coagulative pathways. The presence of VWF in excess in SCD, particularly in its largest multimeric form, greatly contributes to its pathogenesis. Understanding the molecular mechanisms that underly the presence of large VWF multimers in SCD will provide further insight into the pathogenesis of SCD and provide specific targets for therapy., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.)

ADAMTS13 (a disintegrin-like metalloprotease domain with thrombospondin type 1 motif, member 13) is a protease of crucial importance in the regulation of the size of von Willebrand factor multimers. Very low ADAMTS13 activity levels result in thrombotic thrombocytopenic purpura, a rare and life-threatening disease. The mechanisms involved can either be acquired (immune-mediated thrombotic thrombocytopenic purpura [iTTP]) or congenital (cTTP, Upshaw-Schulman syndrome) caused by the autosomal recessive inheritance of disease-causing variants (DCVs) located along the ADAMTS13 gene, which is located in chromosome 9q34. Apart from its role in TTP, and as a regulator of microthrombosis, ADAMTS13 has begun to be identified as a prognostic and/or diagnostic marker of other diseases, such as those related to inflammatory processes, liver damage, metastasis of malignancies, sepsis, and different disorders related to angiogenesis. Since its first description almost 100 years ago, the improvement of laboratory tests and the description of novel DCVs along the ADAMTS13 gene have contributed to a better and faster diagnosis of patients under critical conditions. The ability of ADAMTS13 to dissolve platelet aggregates in vitro and its antithrombotic properties makes recombinant human ADAMTS13 treatment a potential therapeutic approach targeting not only patients with cTTP but also other medical conditions., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: Congenital thrombotic thrombocytopenic purpura is caused by defects in the ADAMTS13 gene. ADAMTS13 is normally preactivated by conformational changes of the Metalloprotease (M) domain. Studying a novel congenital thrombotic thrombocytopenic purpura p.R102S mutation in the M domain, which results in undetectable ADAMTS13 activity in the patient, could help to explain the patients' phenotype and to elucidate the currently unclear mechanism of allosteric preactivation., Objectives: To investigate the in vitro effect of p.R102S mutation on ADAMTS13 secretion, activity, and allosteric preactivation., Methods: Molecular modeling was used to study the effect of the mutation on the stability of ADAMTS13. Recombinant mutant ADAMTS13 was generated by transient and stable transfection of, respectively, CHO K1 and HEK293-T cells. ADAMTS13 antigen was measured in enzyme-linked immunosorbent assay. ADAMTS13 activity was measured in a FRETS-VWF73 assay. Allosteric preactivation was assessed in FRETS-VWF73 assay, using monoclonal antibody (mAb) 17G2 that normally induces a ∼2-fold increase in activity, and in enzyme-linked immunosorbent assay using mAb 6A6 recognizing a cryptic epitope in the M domain that becomes exposed after binding of 17G2., Results: p.R102S mutation destabilizes the interactions between the M and Disintegrin-like (D) domain. p.R102S mutant secretion was impaired (35% of wild type) and activity was severely reduced (12% of wild type). p.R102S mutant could still be activated and the cryptic epitope of 6A6 was still fully exposed by 17G2 addition., Conclusion: p.R102S mutation destabilizes the M-D domain interactions, causing impaired ADAMTS13 secretion and activity, which explains the patients' phenotype. Allosteric preactivation of ADAMTS13 remains conserved in the presence of the p.R102S mutation., (Copyright © 2022 International Society on Thrombosis and Haemostasis. All rights reserved.)

Background: Sickle cell disease (SCD) is an inherited red blood cell disorder with a causative substitution in the beta-globin gene that encodes beta-globin in hemoglobin. Furthermore, the ensuing vasculopathy in the microvasculature involves heightened endothelial cell adhesion, inflammation, and coagulopathy, all of which contribute to vaso-occlusive crisis (VOC) and the sequelae of SCD. In particular, dysregulation of the von Willebrand factor (VWF) and a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13 (ADAMTS13) axis has been implicated in human SCD pathology., Objectives: To investigate the beneficial potential of treatment with recombinant ADAMTS13 (rADAMTS13) to alleviate VOC., Methods: Pharmacologic treatment with rADAMTS13 in vitro or in vivo was performed in a humanized mouse model of SCD that was exposed to hypoxia/reoxygenation stress as a model of VOC. Then, pharmacokinetic, pharmacodynamic, and behavioral analyses were performed., Results: Administration of rADAMTS13 to SCD mice dose-dependently increased plasma ADAMTS13 activity, reduced VWF activity/antigen ratios, and reduced baseline hemolysis (free hemoglobin and total bilirubin) within 24 hours. rADAMTS13 was administered in SCD mice, followed by hypoxia/reoxygenation stress, and reduced VWF activity/antigen ratios in parallel to significantly (p < .01) improved recovery during the reoxygenation phase. Consistent with the results in SCD mice, we demonstrate in a human in vitro system that treatment with rADAMTS13 counteracts the inhibitory activity of hemoglobin on the VWF/ADAMTS13-axis., Conclusion: Collectively, our data provide evidence that relative ADAMTS13 insufficiency in SCD mice is corrected by pharmacologic treatment with rADAMTS13 and provides an effective disease-modifying approach in a human SCD mouse model., Competing Interests: Declaration of competing interest S.C., G.S., and H. Gritsch are employees of Baxalta Innovations GmbH, a member of the Takeda group of companies, and are Takeda stock owners. P.R., H. Glantschnig, F.C., M.S., D.V., M.D., B.P., H.R., F.S., and W.H. were employees of Baxalta Innovations GmbH, a member of the Takeda group of companies, at the time of the study. L.D.F. has received grant/research support from Baxalta Innovations GmbH, a Takeda company; Roche; and Agios. E.F. and A.M. have no competing interests to declare., (Copyright © 2022 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Objective: To report the clinical manifestations and laboratory features of five patients with congenital thrombotic thrombocytopenic purpura (cTTP) and explore its standardized clinical diagnosis and treatment along with a review of literature. Methods: Clinical data of patients, such as age of onset, disease manifestation, personal history, family history, and misdiagnosed disease, were collected. Treatment outcomes, therapeutic effects of plasma infusion, and organ function evaluation were observed. The relationship among the clinical manifestations, treatment outcomes, and ADAMTS13 gene mutation of patients with cTTP was analyzed. Additionally, detection of ADAMTS13 activity and analysis of ADAMTS13 gene mutation were explored. Results: The age of onset of cTTP was either in childhood or adulthood except in one case, which was at the age of 1. The primary manifestations were obvious thrombocytopenia, anemia, and different degrees of nervous system involvement. Most of the patients were initially suspected of having immune thrombocytopenia. Acute cTTP was induced by pregnancy and infection in two and one case, respectively. ADAMTS13 gene mutation was detected in all cases, and there was an inherent relationship between the mutation site, clinical manifestations, and degree of organ injury. Therapeutic or prophylactic plasma transfusion was effective for treating cTTP. Conclusions: The clinical manifestations of cTTP vary among individuals, resulting in frequent misdiagnosis that delays treatment. ADAMTS13 activity detection in plasma and ADAMTS13 gene mutation analysis are important bases to diagnose cTTP. Prophylactic plasma transfusion is vital to prevent the onset of the disease.

Introduction: Severe ADAMTS13 deficiency defines thrombotic thrombocytopenic purpura (TTP). ADAMTS13 is responsible for VWF cleavage. In the absence of this enzyme, widespread thrombi formation occurs, causing microangiopathic anemia and thrombocytopenia and leading to ischemic organ injury. Understanding ADAMTS13 function is crucial to diagnose and manage TTP, both in the immune and hereditary forms., Areas Covered: The role of ADAMTS13 in coagulation homeostasis and the consequences of its deficiency are detailed. Other factors that modulate the consequences of ADAMTS13 deficiency are explained, such as complement system activation, genetic predisposition, or the presence of an inflammatory status. Clinical suspicion of TTP is crucial to start prompt treatment and avoid mortality and sequelae. Available techniques to diagnose this deficiency and detect autoantibodies or gene mutations are presented, as they have become faster and more available in recent years., Expert Opinion: A better knowledge of TTP pathophysiology is leading to an improvement in diagnosis and follow-up, as well as a customized treatment in patients with TTP. This scenario is necessary to define the role of new targeted therapies already available or coming soon and the need to better diagnose and monitor at the molecular level the evolution of the disease.

A 27-year-old patient with a history of severe obstetrical complications and arterial thrombosis received a diagnosis of hereditary thrombotic thrombocytopenic purpura (TTP) due to severe ADAMTS13 deficiency when she presented with an acute episode in the 30th week of her second pregnancy. When the acute episode of hereditary TTP became plasma-refractory and fetal death was imminent, weekly injections of recombinant ADAMTS13 at a dose of 40 U per kilogram of body weight were initiated. The patient's platelet count normalized, and the growth of the fetus stabilized. At 37 weeks 1 day of gestation, a small-for-gestational-age boy was delivered by cesarean section. At the time of this report, the patient and her son were well, and she continued to receive injections of recombinant ADAMTS13 every 2 weeks. (Funded by the Swiss National Science Foundation.)., (Copyright © 2022 Massachusetts Medical Society.)

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., (© 2022 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals LLC on behalf of International Society on Thrombosis and Haemostasis.)

Upshaw-Schulman syndrome (USS)-rare autosomal recessive disease that affects <1/1 000 000 individuals. It is characterized by the massive formation of platelet thrombi in the microcirculation accompanied by haemolytic anaemia, thrombocytopenia and clinical and laboratory signs of renal and neurological failure. USS is caused by mutations in the ADAMTS13 gene. Mutations in the ADAM metallopeptidase with thrombospondin type 1 motif 13  (ADAMTS13) gene can lead to disruption of secretion of this enzyme, or to decrease of enzyme proteinase activity without effect on ADAMTS13 secretion. The aim of this work is to describe a clinical case of USS caused by a new missense mutation in the ADAMTS13 gene. The diagnosis of thrombotic thrombocytopenic purpura was based on clinical signs and confirmed if plasma ADAMTS13 activity was <10%. ADAMTS13 gene sequencing was performed by the Sanger method using oligonucleotide primers of our own design. We found a new, undescribed mutation p.Trp387Ser in a TrpXXTrp motif. Previously, a pathogenic variation disrupting the 387TrpSerSerTrp390 motif of the ADAMTS13 protein was detected only once. Clinical picture of a patient with the combination of the p.Trp387Ser and p.Arg1060Trp variations is quite similar to that of the homozygous state of p.Arg1060Trp variant., (© 2022 John Wiley & Sons Australia, Ltd.)

Background: Severe deficiency of plasma ADAMTS13 activity may result in potentially fatal thrombotic thrombocytopenic purpura and relative deficiency of plasma ADAMTS13 activity may be associated with adverse outcomes of certain malignancies. Here, we report the role of ADAMTS13 or lack of von Willebrand factor (VWF) in reducing irradiation and melanoma-induced thrombotic microangiopathy (TMA) and mortality in zebrafish., Methods: Zebrafish melanoma cell line (ZMEL) was injected subcutaneously into wild-type (wt), adamts13 -/- (a13 -/- ), von Willebrand factor (vwf -/- ), and a13 -/- vwf -/- zebrafish following total body irradiation; the tumor growth, its gene expression pattern, the resulting thrombocytopenia, and the mortality were determined., Results: Total body irradiation at 30 Gy alone resulted in a transient thrombocytopenia in both wt and a13 -/- zebrafish. However, thrombocytopenia occurred earlier and more profound in a13 -/- than in wt zebrafish, which was resolved 2 weeks following irradiation alone. An inoculation of ZMEL following the irradiation resulted in more severe and persistent thrombocytopenia, as well as earlier death in a13 -/- than in wt zebrafish. The vwf -/- or a13 -/- vwf -/- zebrafish were protected from developing severe thrombocytopenia following the same maneuvers. RNA-sequencing revealed significant differentially expressed genes associated with oxidation-reduction, metabolism, lipid, fatty acid and cholesterol metabolic processes, steroid synthesis, and phospholipid efflux in the melanoma explanted from a13 -/- zebrafish compared with that from the wt controls., Conclusions: Our results indicated that plasma ADAMTS13 or lack of VWF may offer a significant protection against the development of irradiation- and/or melanoma-induced TMA. Such a microenvironment may directly affect melanoma cell phenotypes via alternation in the oxidation-reduction and lipid metabolic pathways., (© 2022 International Society on Thrombosis and Haemostasis.)

Background: Recombinant human ADAMTS13 (rADAMTS13) is a key protein in fundamental research for investigating its mode of action and the pathophysiology of thrombotic thrombocytopenic purpura (TTP). However, the expression of rADAMTS13 is quite low in mammalian cells, which makes the production of the protein time-consuming and labor-intensive., Objectives: We aimed at increasing the yield of rADAMTS13 by (1) using a more optimal signal peptide (SP) and (2) constructing an N-terminal fusion protein of ADAMTS13 with human serum albumin domain 1 (AD1-ADAMTS13)., Methods: Six SPs were investigated to select the most optimal SP. Expression plasmids containing the most optimal SP and ADAMTS13 cDNA or the fusion construct AD1-ADAMTS13 were generated and transiently transfected into CHOEBNALT85 cell-line. Expression levels of rADAMTS13 in expression medium were analyzed and compared with the expression level of rADAMTS13 with native SP (nat-SP)., Results: Expression of rADAMTS13 with coagulation factor VII (FVII) SP was 3-fold higher (16.00 μg/ml) compared with the expression with nat-SP (5.03 μg/ml). The highest yields were obtained with AD1-ADAMTS13 protein with a 15-fold higher concentration (78.22 μg/ml) compared with the expression with nat-SP. The rADAMTS13 expressed with FVII-SP retained its activity (104.0%) to cleave von Willebrand factor, whereas AD1-ADAMTS13 demonstrated even higher activity (144.3%)., Conclusion: We succeeded in generating expression vectors that yield (1) rADAMTS13 at higher levels because of more optimal FVII-SP and (2) high levels of AD1-ADAMTS13 N-terminal fusion protein. The highest expression levels were obtained with AD1-ADAMTS13 N-terminal fusion protein, which is paving the way for highly efficient protein production., (© 2022 International Society on Thrombosis and Haemostasis.)

The effects of synonymous single nucleotide variants (sSNVs) are often neglected because they do not alter protein primary structure. Nevertheless, there is growing evidence that synonymous variations may affect messenger RNA (mRNA) expression and protein conformation and activity, which may lead to protein deficiency and disease manifestations. Because there are >21 million possible sSNVs affecting the human genome, it is not feasible to experimentally validate the effect of each sSNV. Here, we report a comprehensive series of in silico analyses assessing sSNV impact on a specific gene. ADAMTS13 was chosen as a model for its large size, many previously reported sSNVs, and associated coagulopathy thrombotic thrombocytopenic purpura. Using various prediction tools of biomolecular characteristics, we evaluated all ADAMTS13 sSNVs registered in the National Center for Biotechnology Information database of single nucleotide polymorphisms, including 357 neutral sSNVs and 19 sSNVs identified in patients with thrombotic thrombocytopenic purpura. We showed that some sSNVs change mRNA-folding energy/stability, disrupt mRNA splicing, disturb microRNA-binding sites, and alter synonymous codon or codon pair usage. Our findings highlight the importance of considering sSNVs when assessing the complex effects of ADAMTS13 alleles, and our approach provides a generalizable framework to characterize sSNV impact in other genes and diseases., (Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Thrombosis of small and large vessels is reported as a key player in COVID-19 severity. However, host genetic determinants of this susceptibility are still unclear. Congenital Thrombotic Thrombocytopenic Purpura is a severe autosomal recessive disorder characterized by uncleaved ultra-large vWF and thrombotic microangiopathy, frequently triggered by infections. Carriers are reported to be asymptomatic. Exome analysis of about 3000 SARS-CoV-2 infected subjects of different severities, belonging to the GEN-COVID cohort, revealed the specific role of vWF cleaving enzyme ADAMTS13 (A disintegrin-like and metalloprotease with thrombospondin type 1 motif, 13). We report here that ultra-rare variants in a heterozygous state lead to a rare form of COVID-19 characterized by hyper-inflammation signs, which segregates in families as an autosomal dominant disorder conditioned by SARS-CoV-2 infection, sex, and age. This has clinical relevance due to the availability of drugs such as Caplacizumab, which inhibits vWF-platelet interaction, and Crizanlizumab, which, by inhibiting P-selectin binding to its ligands, prevents leukocyte recruitment and platelet aggregation at the site of vascular damage.

Congenital thrombotic thrombocytopenic purpura, also known as Upshaw-Schulman syndrome, is a rare autosomal recessive genetic disorder. The main pathogenesis is homozygous or compound heterozygous variants of von Willebrand factor lyase (ADAMTS13) gene mapped to chromosome 9q34, which may result in severe lack of ADAMTS13 which cleaves von Willebrand factor (vWF) multimers in the plasma and increase the risk of microvascular thrombosis, leading to various complications. The advance of research on the pathogenesis of cTTP, recombinant human ADAMTS13 and gene therapy have made breakthroughs which may lead to cure of cTTP. This article has provided a review for the latest progress made in the diagnosis and treatment of cTTP.

Congenital thrombotic thrombocytopenic purpura (cTTP) is caused by ADAMTS13 mutations and associated with high risk of microvascular thrombosis. A 58 year old female had an ischemic stroke during hormonal fertility, and a TIA a year after. She suffered another stroke 18 years later while on warfarin. Four months after she developed severe thrombocytopenia, mild anemia, and increased LDH. Blood film showed schistocytes. She was hospitalized with presumptive TTP. ADAMTS 13 activity was undetectable without inhibitor. She developed another stroke and received plasma exchange. A homozygote ADAMTS 13 mutation was identified. Despite plasma, the ADAMTS13 activity remained < 10% and she had another stroke. Recombinant ADAMTS13 therapy was obtained through compassionate use. She receives weekly infusions maintaining ADAMTS13 trough levels above 10% without thrombotic recurrences. This case underscores the need to recognize cTTP as a cause of cryptogenic strokes, and the diagnostic value of the peripheral blood film. rADAMTS13 replacement may prevent recurrences., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Upshaw-Schulman syndrome is a rare congenital form of thrombotic thrombocytopenic purpura (TTP) characterized by single or recurrent episodes of thrombocytopenia, microangiopathic hemolyticanemia (MAHA), and widespread microvascular thrombosis, leading to the ischemic damage of multiple organs (mainly kidney, heart and brain). A 6-mo-old female infant, second born of a third-degree consanguineous marriage, with a history of severe neonatal jaundice with thrombocytopenia secondary to hemolysis requiring exchange transfusion on day 2 of life, presented with high-grade fever without focus of 2-d duration. Initial workup revealed microangiopathic hemolyticanemia with thrombocytopenia. In view of microangiopathic hemolyticanemia with thrombocytopenia against a background of severe neonatal jaundice, a diagnosis of congenital TTP was considered and was managed with FFP transfusion. The diagnosis was confirmed with her exome sequencing showing autosomal recessive homozygous frameshift deletion c.2063delG (p.Trp688fs) at Exon 17 (NM&#95;139025) of ADAMTS 13 gene., (© 2022. Dr. K C Chaudhuri Foundation.)

Preeclampsia (PE) constitutes one of the principal reasons for maternal and perinatal morbidity and mortality worldwide. The circumstance typically implicates formerly healthful normotensive women, after 20 weeks of gestation, typically withinside the third trimester, without regarded threat elements or past deliveries. PE can be further complicated with hemolysis and thrombocytopenia, leading to the emergence of HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low platelets). Both conditions are classified as hypertensive diseases of pregnancy (HDP), and their pathogenesis has been linked to an excessive maternal inflammatory response, accompanied by enhanced endothelial activation. Several studies have found that in pregnancies affected by PE/HELLP, von Willebrand factor (vWF) antigen levels (vWF:Ag) are significantly elevated, while its cleaving protease (ADAMTS-13, A Disintegrin-like and Metalloprotease with Thrombospondin type 1 motif, member 13) activity is normal to decreased. Furthermore, the higher urine excretion of the terminal complement complex C5b-9, as well as its greater deposition in the placental surface in preeclamptic women, imply that the utero-placental unit's distinctive deficits are intimately tied to disproportionate complement activation. The goal of this updated evaluation is to provide the most up-to-date molecular advances in the pathophysiology of PE/HELLP syndromes. Recent medical data on vWF:Ag levels in patients with PE, ADAMTS-13, and dysregulation of the complement system, are highlighted and evaluated. Furthermore, we discuss the relationship between those entities and the progression of the disease, as well as their significance in the diagnostic process. Finally, considering the difficulties in analyzing and controlling those symptoms in pregnant women, we can provide a current diagnostic and therapeutic algorithm.

Advances in our understanding of ADAMTS13 structure, and the conformation changes required for full activity, have rejuvenated the possibility of its use as a thrombolytic therapy. We have tested a novel Ala1144Val ADAMTS13 variant (constitutively active [ca] ADAMTS13) that exhibits constitutive activity, characterized using in vitro assays of ADAMTS13 activity, and greatly enhanced thrombolytic activity in 2 murine models of ischemic stroke, the distal FeCl3 middle cerebral artery occlusion (MCAo) model and transient middle cerebral artery occlusion (tMCAO) with systemic inflammation and ischemia/reperfusion injury. The primary measure of efficacy in both models was restoration of regional cerebral blood flow (rCBF) to the MCA territory, which was determined using laser speckle contrast imaging. The caADAMTS13 variant exhibited a constitutively active conformation and a fivefold enhanced activity against fluorescence resonance energy transfer substrate von Willebrand factor 73 (FRETS-VWF73) compared with wild-type (wt) ADAMTS13. Moreover, caADAMTS13 inhibited VWF-mediated platelet capture at subphysiological concentrations and enhanced t-PA/plasmin lysis of fibrin(ogen), neither of which were observed with wtADAMTS13. Significant restoration of rCBF and reduced lesion volume was observed in animals treated with caADAMTS13. When administered 1 hour after FeCl3 MCAo, the caADAMTS13 variant significantly reduced residual VWF and fibrin deposits in the MCA, platelet aggregate formation, and neutrophil recruitment. When administered 4 hours after reperfusion in the tMCAo model, the caADAMTS13 variant induced a significant dissolution of platelet aggregates and a reduction in the resulting tissue hypoperfusion. The caADAMTS13 variant represents a potentially viable therapeutic option for the treatment of acute ischemic stroke, among other thrombotic indications, due to its enhanced in vitro and in vivo activities that result from its constitutively active conformation., (© 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Immune thrombotic thrombocytopenic purpura (iTTP) is an ultra-rare, life-threatening disorder, mediated through severe ADAMTS13 deficiency causing multi-system micro-thrombi formation, and has specific human leukocyte antigen associations. We undertook a large genome-wide association study to investigate additional genetically distinct associations in iTTP. We compared two iTTP patient cohorts with controls, following standardized genome-wide quality control procedures for single-nucleotide polymorphisms and imputed HLA types. Associations were functionally investigated using expression quantitative trait loci (eQTL), and motif binding prediction software. Independent associations consistent with previous findings in iTTP were detected at the HLA locus and in addition a novel association was detected on chromosome 3 (rs9884090, P=5.22x10-10, odds ratio 0.40) in the UK discovery cohort. Meta-analysis, including the French replication cohort, strengthened the associations. The haploblock containing rs9884090 is associated with reduced protein O-glycosyltransferase 1 (POGLUT1) expression (eQTL P<0.05), and functional annotation suggested a potential causative variant (rs71767581). This work implicates POGLUT1 in iTTP pathophysiology and suggests altered post-translational modification of its targets may influence disease susceptibility.

We report on a 12-year-old boy with congenital thrombotic thrombocytopenic purpura, on who had an erroneous diagnosis as chronic immune thrombocytopenia. The patient presented with complaints of jaundice and skin rash. Laboratory analysis showed nonimmune hemolytic anemia and severe thrombocytopenia. Peripheral blood smear showed 8% schistocytes, polychromasia, and anisocytosis. The ADAMTS13 antigen and activity were suspected to be lower than 5% with any antibodies against the enzyme. The DNA sequence analyses resulted in compound heterozygosity consisting of c.291&#95;391del in exon 3 and c.4143dupA in exon 29. Schistocyte (fragmented erythrocytes) on the peripheral blood smear is a light that illuminates the diagnosis. Early recognition of the disease can prevent inappropriate treatments and morbidities due to organ damage., Competing Interests: The authors declare no conflict of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: ADAMTS13 cleaves von Willebrand factor (VWF) multimers into less active fragments. Both markers have been related to cardiovascular disease (CVD). We aimed to investigate the influence of ADAMTS13 single nucleotide polymorphisms (SNPs) on levels of ADAMTS13 and VWF, and CVD., Methods: The c.1342C>G, g.41635A>G and c.2699C>T polymorphisms were determined in patients with chronic coronary syndrome (n = 1000). VWF and ADAMTS13 were analyzed. Clinical endpoints after 2 years (n = 106) were unstable angina pectoris, myocardial infarction, non-hemorrhagic stroke and death., Results: The SNPs did not affect ADAMTS13 levels. The 41635A-allele associated with higher VWF levels ( P  < .001). Patients with the 1342G-allele had significantly higher frequency of previous atrial fibrillation (n = 26, P  = .016) and cerebral ischemic events (n = 47, P  = .030). Heterozygous of the 1342CG variant experienced more clinical endpoints compared to homozygous (CC and GG) ( P  = .028)., Conclusion: The association between the 41635A-allele and VWF indicates a role for this polymorphism in VWF regulation. ADAMTS13 has previously been linked to atrial fibrillation and ischemic stroke, and our findings suggest that the 1342G-allele may be of significance. The association between the 1342CG genotype and endpoints needs further investigations.Clinicaltrials.gov, ASCET, NCT00222261. https://clinicaltrials.gov/ct2/show/NCT00222261?term=NCT00222261&draw=2&rank=1.

Background: Mutations in the ADAMTS13 gene can lead to an ADAMTS13 enzyme deficiency, which is related to Upshaw-Schulman syndrome (USS). USS is a common type of thrombotic thrombocytopenic purpura (TTP). Here we present a very rare case of TTP caused by 2 mutations in the ADAMTS13 gene. Besides, we reviewed and summarized previous pathogenic ADAMTS13 gene mutations associated with the TTP., Case Presentation: A 10-year-old female was admitted to the Third Xiangya Hospital of Central South University after experiencing discontinuous thrombocytopenia for 8 years, abnormal renal function for more than 2 years, cough for more than 10 days, and weakness of the left limb for 3 days. Gene sequencing shows the patient's ADAMTS13 gene contains compound heterozygous nucleotide variations: c.1335delC (p. Phe445LeufsTer52) is a frameshift variation inherited from her father and c.2130C > G (p. Cys710Trp) is a missense variation inherited from her mother. The final diagnosis was USS., Conclusions: Our study reports a very rare genetic TTP case caused by two compound heterozygous variants in the ADAMTS13 gene. The effect of these two mutations on the secretion of ADAMTS13 requires further in vitro experiments to confirm., (© 2021. The Author(s).)

Background: We previously described the association between rare ADAMTS13 single nucleotide variants (SNVs) and deep vein thrombosis (DVT). Moreover, DVT patients with at least one rare ADAMTS13 SNV had a lower ADAMTS13 activity than non-carriers., Aims: To confirm ADAMTS13 variants association with DVT and reduced plasma ADAMTS13 activity levels in a larger population. To investigate the role of VWF and F8 variants., Methods: ADAMTS13, VWF and F8 were sequenced using next-generation sequencing in 594 Italian DVT patients and 571 controls. Genetic association testing was performed using logistic regression and gene-based tests. The association between rare ADAMTS13 variants and the respective plasmatic activity, available for 365 cases and 292 controls, was determined using linear regression. All analyses were age-, sex- adjusted., Results: We identified 48 low-frequency/common and 272 rare variants. Nine low-frequency/common variants had a P<0.05, but a false discovery rate between 0.06 and 0.24. Of them, 7 were found in ADAMTS13 (rs28641026, rs28503257, rs685523, rs3124768, rs3118667, rs739469, rs3124767; all protective) and 2 in VWF (rs1800382 [risk], rs7962217 [protective]). Rare ADAMTS13 variants were significantly associated with DVT using the burden, variable threshold (VT) and UNIQ (P<0.05), but not with C-ALPHA, SKAT and SKAT-O tests. Rare VWF and F8 variants were not associated with DVT. Carriers of rare ADAMTS13 variants had lower ADAMTS13 activity than non-carriers (ß -6.2, 95%CI -11,-1.5). This association was stronger for DVT patients than controls (ß -7.5, 95%CI -13.5,-1.5 vs. ß -2.9, 95%CI -10.4,4.5)., Conclusions: ADAMTS13 and VWF low-frequency/common variants mainly showed a protective effect, although their association with DVT was not confirmed. DVT patients carrying a rare ADAMTS13 variants had slightly reduced ADAMTS13 activity levels, but a higher DVT risk. Rare VWF and FVIII variants were not associated with DVT suggesting that other mechanisms are responsible for the high VWF and FVIII levels measured in DVT patients., Competing Interests: F. P. reports participation at educational meetings and advisory board of Sanofi, Sobi, Takeda and Roche. I. M. received honoraria for participating as a speaker at educational meetings organized by Instrumentation Laboratory and Sanofi-Genzyme. The other authors state that they have no conflict of interest. This does not alter our adherence to PLOS ONE policies on sharing data and materials