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Data are available on request from the corresponding author, R. Pawlinski (rafal_pawlinski@med.unc.edu). The online version of this article contains a data supplement. The American Society of Hematology A hypercoagulable state, chronic inflammation, and increased risk of venous thrombosis and stroke are prominent features in patients with sickle cell disease (SCD). Coagulation factor XII (FXII) triggers activation of the contact system that is known to be involved in both thrombosis and inflammation, but not in physiological hemostasis. Therefore, we investigated whether FXII contributes to the prothrombotic and inflammatory complications associated with SCD. We found that when compared with healthy controls, patients with SCD exhibit increased circulating biomarkers of FXII activation that are associated with increased activation of the contact pathway. We also found that FXII, but not tissue factor, contributes to enhanced thrombin generation and systemic inflammation observed in sickle cell mice challenged with tumor necrosis factor α. In addition, FXII inhibition significantly reduced experimental venous thrombosis, congestion, and microvascular stasis in a mouse model of SCD. Moreover, inhibition of FXII attenuated brain damage and reduced neutrophil adhesion to the brain vasculature of sickle cell mice after ischemia/reperfusion induced by transient middle cerebral artery occlusion. Finally, we found higher FXII, urokinase plasminogen activator receptor, and αMβ2 integrin expression in neutrophils of patients with SCD compared with healthy controls. Our data indicate that targeting FXII effectively reduces experimental thromboinflammation and vascular complications in a mouse model of SCD, suggesting that FXII inhibition may provide a safe approach for interference with inflammation, thrombotic complications, and vaso-occlusion in patients with SCD. This work was funded in part by National Institutes of Health (NIH) R01s HL142604 (RP), HL157441 (RP, NK) and NIH U01 HL117659 (RP, NK). EMS is supported by NIH R01 HL 155193. MK was supported by R00HL144817 from NHLBI and UAB AMC21 MULTIPI6724 grant. GMV and JDB were supported by research funding from NIH 5R01 HL114567. TR acknowledges Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) grants P6 - KFO306, 80750187 - SFB841 and 470698011 -SFB877. DG was supported by NIH R35 HL140025. FG was supported by Royal Society Wolfson Foundation (RSWF\R3\183001). AG and MW were supported by NIH R44 HL126235. This work was supported by the NIH R01 HL137695 (E.X.S.), Merit Review Awards BX003851 (E.X.S.) and the Oscar D. Ratnoff Endowed Professorship (E.X.S.). The contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH, the U.S. Department of Veterans Affairs, or the United States Government.

Targeted drug delivery to disease-associated activated neutrophils can provide novel therapeutic opportunities while avoiding systemic effects on immune functions. We created a nanomedicine platform that uniquely utilizes an α(1)-antitrypsin-derived peptide to confer binding specificity to neutrophil elastase on activated neutrophils. Surface decoration with this peptide enabled specific anchorage of nanoparticles to activated neutrophils and platelet–neutrophil aggregates, in vitro and in vivo. Nanoparticle delivery of a model drug, hydroxychloroquine, demonstrated significant reduction of neutrophil activities in vitro and a therapeutic effect on murine venous thrombosis in vivo. This innovative approach of cell-specific and activation-state-specific targeting can be applied to several neutrophil-driven pathologies.

SARS-CoV-2 vaccine ChAdOx1 nCoV-19 (AstraZeneca) causes a thromboembolic complication termed vaccine-induced immune thrombotic thrombocytopenia (VITT). Using biophysical techniques, mouse models, and analysis of VITT patient samples, we identified determinants of this vaccine-induced adverse reaction. Super-resolution microscopy visualized vaccine components forming antigenic complexes with platelet factor 4 (PF4) on platelet surfaces to which anti-PF4 antibodies obtained from VITT patients bound. PF4/vaccine complex formation was charge-driven and increased by addition of DNA. Proteomics identified substantial amounts of virus production-derived T-REx HEK293 proteins in the ethylenediaminetetraacetic acid (EDTA)-containing vaccine. Injected vaccine increased vascular leakage in mice, leading to systemic dissemination of vaccine components known to stimulate immune responses. Together, PF4/vaccine complex formation and the vaccine-stimulated proinflammatory milieu trigger a pronounced B-cell response that results in the formation of high-avidity anti-PF4 antibodies in VITT patients. The resulting high-titer anti-PF4 antibodies potently activated platelets in the presence of PF4 or DNA and polyphosphate polyanions. Anti-PF4 VITT patient antibodies also stimulated neutrophils to release neutrophil extracellular traps (NETs) in a platelet PF4-dependent manner. Biomarkers of procoagulant NETs were elevated in VITT patient serum, and NETs were visualized in abundance by immunohistochemistry in cerebral vein thrombi obtained from VITT patients. Together, vaccine-induced PF4/adenovirus aggregates and proinflammatory reactions stimulate pathologic anti-PF4 antibody production that drives thrombosis in VITT. The data support a 2-step mechanism underlying VITT that resembles the pathogenesis of (autoimmune) heparin-induced thrombocytopenia.

Contact activation refers to the process of surface-induced activation of factor XII (FXII), which initiates blood coagulation and is captured by the activated partial thromboplastin time (aPTT) assay. Here, we show the mechanism and diagnostic implications of FXII contact activation. Screening of recombinant FXII mutants identified a continuous stretch of residues Gln317–Ser339 that was essential for FXII surface binding and activation, thrombin generation and coagulation. Peptides spanning these 23 residues competed with surface-induced FXII activation. Although FXII mutants lacking residues Gln317–Ser339 were susceptible to activation by plasmin and plasma kallikrein, they were ineffective in supporting arterial and venous thrombus formation in mice. Antibodies raised against the Gln317–Ser339 region induced FXII activation and triggered controllable contact activation in solution leading to thrombin generation by the intrinsic pathway of coagulation. The antibody-activated aPTT allows for standardization of particulate aPTT reagents and for sensitive monitoring of coagulation factors VIII, IX, XI., Blood coagulation is started by contact to surfaces and this is the principle for a commonly used diagnostic clotting test, aPTT. Here, the authors identify the structure in coagulation factor XII that initiates surface-driven coagulation and use the information to develop improved aPTT assays.

This research was originally published in Blood. Mailer, Allende, Heestermans, Schweizer, Deppermann, Frye, Pula, Odeberg, Gelderblom, Rose-John, Sickmann, Blankenberg, Huber, Kubisch, Maas, Gambaryan, Firsov, Stavrou, Butler, Renné. Xenotropic and polytropic retrovirus receptor 1 regulates procoagulant platelet polyphosphate. Blood. 2021;137(10):1392-1405. © the American Society of Hematology. Polyphosphate is a procoagulant inorganic polymer of linear-linked orthophosphate residues. Multiple investigations have established the importance of platelet polyphosphate in blood coagulation; however, the mechanistic details of polyphosphate homeostasis in mammalian species remain largely undefined. In this study, xenotropic and polytropic retrovirus receptor 1 (XPR1) regulated polyphosphate in platelets and was implicated in thrombosis in vivo. We used bioinformatic analyses of omics data to identify XPR1 as a major phosphate transporter in platelets. XPR1 messenger RNA and protein expression inversely correlated with intracellular polyphosphate content and release. Pharmacological interference with XPR1 activity increased polyphosphate stores, led to enhanced platelet-driven coagulation, and amplified thrombus formation under flow via the polyphosphate/factor XII pathway. Conditional gene deletion of Xpr1 in platelets resulted in polyphosphate accumulation, accelerated arterial thrombosis, and augmented activated platelet-driven pulmonary embolism without increasing bleeding in mice. These data identify platelet XPR1 as an integral regulator of platelet polyphosphate metabolism and reveal a fundamental role for phosphate homeostasis in thrombosis.

Background There are acute settings where assessing the anticoagulant effect of direct oral anticoagulants (DOACs) can be useful. Due to variability among routine coagulation tests, there is an unmet need for an assay that detects DOAC effects within minutes in the laboratory or at the point of care. Methods We developed a novel dielectric microsensor, termed ClotChip, and previously showed that the time to reach peak permittivity (T peak) is a sensitive parameter of coagulation function. We conducted a prospective, single-center, pilot study to determine its clinical utility at detecting DOAC anticoagulant effects in whole blood. Results We accrued 154 individuals: 50 healthy volunteers, 49 rivaroxaban patients, 47 apixaban, and 8 dabigatran patients. Blood samples underwent ClotChip measurements and plasma coagulation tests. Control mean T peak was 428 seconds (95% confidence interval [CI]: 401–455 seconds). For rivaroxaban, mean T peak was 592 seconds (95% CI: 550–634 seconds). A receiver operating characteristic curve showed that the area under the curve (AUC) predicting rivaroxaban using T peak was 0.83 (95% CI: 0.75–0.91, p Conclusion This diagnostic study using samples from “real-world” DOAC patients supports that ClotChip exhibits high sensitivity at detecting DOAC anticoagulant effects in a disposable portable platform, using a miniscule amount of whole blood (

The mechanism of aging is not yet fully understood. It has been recognized that there are age-dependent changes in the DNA methylation pattern of the whole genome. To date, there are several DNA methylation-based estimators of the chronological age. A majority of the estimators use the DNA methylation data from a single tissue type, such as blood. In 2013, for the first time, Steve Horvath reported the DNA methylation-based age estimator (353 CpGs were used) that could be applied to multiple tissues. A refined, more sensitive version that uses 391 CpGs was subsequently developed and validated in human cells, including fibroblasts. In this review, the age predicted by DNA methylation-based age estimator is referred to as DNAmAge, and the biological process controlling the progression of DNAmAge is referred to as the epigenetic aging in this minireview. The concepts of DNAmAge and epigenetic aging provide us opportunities to discover previously unrecognized biological events controlling aging. In this article, we discuss the frequently asked questions regarding DNAmAge and the epigenetic aging by introducing recent studies of ours and others. We focus on addressing the following questions: (1) Is there any synchronization of DNAmAge between cells in a human body?, (2) Can we use in vitro (cell culture) systems to study the epigenetic aging?, (3) Is there an age limit of DNAmAge?, and (4) Is it possible to change the speed and direction of the epigenetic aging? We describe our current understandings to these questions and outline potential future directions. Impact statement Aging is associated with DNA methylation (DNAm) changes. Recent advancement of the whole-genome DNAm analysis technology allowed scientists to develop DNAm-based age estimators. A majority of these estimators use DNAm data from a single tissue type such as blood. In 2013, a multi-tissue age estimator using DNAm pattern of 353 CpGs was developed by Steve Horvath. This estimator was named “epigenetic clock”, and the improved version using DNAm pattern of 391 CpGs was developed in 2018. The estimated age by epigenetic clock is named DNAmAge. DNAmAge can be used as a biomarker of aging predicting the risk of age-associated diseases and mortality. Although the DNAm-based age estimators were developed, the mechanism of epigenetic aging is still enigmatic. The biological significance of epigenetic aging is not well understood, either. This minireview discusses the current understanding of the mechanism of epigenetic aging and the future direction of aging research.

Background: The VA Northeast Ohio Healthcare System introduced a new nurse-driven anti–factor Xa (anti-Xa) protocol for monitoring unfractionated heparin to replace the previous activated partial thromboplastin time protocol. Objective: To design, implement, and evaluate the efficacy of the anti-Xa monitoring protocol. Methods: An interdisciplinary team of providers collaborated to develop and implement a nurse-driven, facility-wide anti–factor Xa protocol for monitoring unfractionated heparin therapy. The effectiveness of this protocol was evaluated by retrospective analysis. Results: We reviewed 100 medical records for compliance with the new anti-Xa monitoring protocol. We then evaluated 178 patients whose anticoagulation was monitored with the anti-Xa assay to determine the time to therapeutic range. We found that 80% of patients receiving the anti-Xa protocol achieved therapeutic anticoagulation within 24 hours, as compared with 54% of patients receiving the activated partial thromboplastin time protocol (P < .001). Protocol conversion also yielded a decrease in blood draws, dose adjustments, and potential calculation errors. Conclusions: Monitoring intravenous heparin therapy with the anti-Xa assay rather than activated partial thromboplastin time resulted in a shorter time to therapeutic anticoagulation, longer maintenance of therapeutic levels, and fewer laboratory tests and heparin dosage changes. We believe the current practice of monitoring heparin treatment with activated partial thromboplastin time assays should be reexamined.

Neutrophil recruitment to the inflamed endothelium is a multistep process and is of utmost importance in the development of the hallmark vaso-occlusive crisis in sickle cell disease (SCD). However, there lacks a standardized, clinically feasible approach for assessing neutrophil recruitment to the inflamed endothelium for individualized risk stratification and therapeutic response prediction in SCD. Here, we describe a microfluidic device functionalized with E-selectin, a critical endothelial receptor for the neutrophil recruitment process, as a strategy to assess neutrophil binding under physiologic flow in normoxia and clinically relevant hypoxia in SCD. We show that hypoxia significantly enhances neutrophil binding to E-selectin and promotes the formation of neutrophil-platelet aggregates. Moreover, we identified two distinct patient populations: a more severe clinical phenotype with elevated lactate dehydrogenase levels and absolute reticulocyte counts but lowered fetal hemoglobin levels associated with constitutively less neutrophil binding to E-selectin. Mechanistically, we demonstrate that the extent of neutrophil activation correlates with membrane L-selectin shedding, resulting in the loss of ligand interaction sites with E-selectin. We also show that inhibition of E-selectin significantly reduces leukocyte recruitment to activated endothelial cells. Our findings add mechanistic insight into neutrophil-endothelial interactions under hypoxia and provide a clinically feasible means for assessing neutrophil binding to E-selectin using clinical whole blood samples, which can help guide therapeutic decisions for SCD patients.

Factor XII (FXII) becomes a serine protease when blood is exposed to artificial medical surfaces or when pathologic surfaces arise in disease states leading to its autoactivation. Initiation of the blood coagulation cascade was the first recognized activity of FXIIa. Blocking FXIIa activity formed on artificial medical surfaces should reduce induced blood coagulation leading to thrombosis. In contrast to FXII enzymatic activities, less is known about zymogen FXII functions. Studies show that zymogen FXII has biologic activity in various cells in vivo. In endothelium, FXII stimulates cell growth and proliferation and, in vivo, neoangiogenesis after injury. In fibroblasts, transforming growth factor‐β increases FXII expression, which in turn stimulates fibroblast proliferation, contributing to tissue fibrosis. In neutrophils, FXII stimulates Akt2 to initiate neutrophil adhesion, migration, and chemotaxis, priming events leading to NETosis. Factor FXII deficiency leads to decreased neutrophil recruitment and improved wound healing. In dendritic cells, FXII contributes to neuroinflammation, and its deficiency or pharmacologic inhibition renders mice less susceptible to autoimmune encephalomyelitis. These combined studies indicate that FXII also contributes to multiple components of the inflammatory response. In sum, targeting FXII's biologic activities may provide novel approaches to reduce thrombosis and the inflammatory response in various disease states.

Key Points Ponatinib therapy heightens arterial thrombosis and platelet reactivity. Concurrent pioglitazone treatment reverses heightened thrombosis risk and platelet reactivity induced by ponatinib.

Targeted drug delivery to disease-associated activated neutrophils can provide novel therapeutic opportunities while avoiding systemic effects on immune functions. We created a nanomedicine platform that uniquely utilizes an α

BackgroundCoagulopathy and inflammation are hallmarks of Coronavirus disease 2019 (COVID-19) and are associated with increased mortality. Clinical and experimental data have revealed a role for neutrophil extracellular traps (NETs) in COVID-19 disease. The mechanisms that drive thrombo-inflammation in COVID-19 are poorly understood.MethodsWe performed proteomic analysis and immunostaining of postmortem lung tissues from COVID-19 patients and patients with other lung pathologies. We further compared coagulation factor XII (FXII) and DNase activities in plasma samples from COVID-19 patients and healthy control donors and determined NET-induced Factor XIII (FXII) activation using a chromogenic substrate assay.FindingsFXII expression and activity were increased in the lung parenchyma, within the pulmonary vasculature and in fibrin-rich alveolar spaces of postmortem lung tissues from COVID-19 patients. In agreement with this, plasma FXII activation (FXIIa) was increased in samples from COVID-19 patients. Furthermore, FXIIa colocalized with NETs in COVID-19 lung tissue indicating that NETs accumulation leads to FXII contact activation in COVID-19. We further showed that an accumulation of NETs is partially due to impaired NET clearance by extracellular DNases as DNase substitution improved NET dissolution and reduced FXII activationin vitro.InterpretationCollectively, our study supports that the NETs/FXII axis contributes to the pathogenic chain of procoagulant and proinflammatory responses in COVID-19. Targeting both, NETs and FXIIa, could provide a strategy to mitigate COVID-19-induced thrombo-inflammation.FundingThis study was supported by the European Union (840189), the Werner Otto Medical Foundation Hamburg (8/95) and the German Research Foundation (FR4239/1-1, A11/SFB877, B08/SFB841 and P06/KFO306).

The mechanism of aging is not yet fully understood. It has been recognized that there are age-dependent changes in the DNA methylation pattern of the whole genome. To date, there are several DNA methylation-based estimators of the chronological age. A majority of the estimators use the DNA methylation data from a single tissue type, such as blood. In 2013, for the first time, Steve Horvath reported the DNA methylation-based age estimator (353 CpGs were used) that could be applied to multiple tissues. A refined, more sensitive version that uses 391 CpGs was subsequently developed and validated in human cells, including fibroblasts. In this review, the age predicted by DNA methylation-based age estimator is referred to as DNAmAge, and the biological process controlling the progression of DNAmAge is referred to as the epigenetic aging in this minireview. The concepts of DNAmAge and epigenetic aging provide us opportunities to discover previously unrecognized biological events controlling aging. In this article, we discuss the frequently asked questions regarding DNAmAge and the epigenetic aging by introducing recent studies of ours and others. We focus on addressing the following questions: (1) Is there any synchronization of DNAmAge between cells in a human body?, (2) Can we use in vitro (cell culture) systems to study the epigenetic aging?, (3) Is there an age limit of DNAmAge?, and (4) Is it possible to change the speed and direction of the epigenetic aging? We describe our current understandings to these questions and outline potential future directions. IMPACT STATEMENT: Aging is associated with DNA methylation (DNAm) changes. Recent advancement of the whole-genome DNAm analysis technology allowed scientists to develop DNAm-based age estimators. A majority of these estimators use DNAm data from a single tissue type such as blood. In 2013, a multi-tissue age estimator using DNAm pattern of 353 CpGs was developed by Steve Horvath. This estimator was named “epigenetic clock”, and the improved version using DNAm pattern of 391 CpGs was developed in 2018. The estimated age by epigenetic clock is named DNAmAge. DNAmAge can be used as a biomarker of aging predicting the risk of age-associated diseases and mortality. Although the DNAm-based age estimators were developed, the mechanism of epigenetic aging is still enigmatic. The biological significance of epigenetic aging is not well understood, either. This minireview discusses the current understanding of the mechanism of epigenetic aging and the future direction of aging research.

Introduction: Sickle Cell Disease (SCD) is characterized by chronic inflammation with innate immune cell activation, especially observed in neutrophils. Emerging evidence implicates the imbalance between neutrophil extracellular trap (NET) formation and degradation as having a central role in the pathophysiology of thromboinflammation and venous thrombosis. Although NETosis and NET formation influences venous thromboembolism (VTE) pathophysiology, little is known about baseline and agonist-induced NETosis in SCD. We hypothesized that systemic neutrophil activation would lead to higher baseline and agonist induced NETosis in SCD and would influence phenotypic variability. To test this hypothesis, we assessed baseline and agonist induced NETosis in patients with SCD and ethnic matched controls. We also investigated the anti-inflammatory effects of flavonoid Quercetin on neutrophil activation. Methods: Neutrophils negatively selected from citrate anticoagulated blood using an immunomagnetic bead based kit (MACSxpress® Miltenyi Biotec) were either fixed immediately to assess baseline NETosis or stimulated with fMLP (1 µM) for 1 hour to assess agonist-induced NETosis. To study flavonoid anti-inflammatory effects, neutrophils were pretreated with Quercetin (100 µM) for 30 min prior to fixation and fMLP stimulation. NETosis was assessed by flow cytometry. Extracellular DNA extrusion on neutrophils was detected by gating the neutrophil population staining with Sytox green. Sytox green positive neutrophils that were positive for both myeloperoxidase (MPO) and tri-Citrullinated Histones (H3Cit) were defined as undergoing NETosis. In some experiments, NET formation was independently confirmed by image flow cytometry (AMNIS). Results: Subjects included SCD patients (genotype SS n=11) and ethnic matched controls (genotype AA, n=11) with a median age of 49 years (p=0.58) and a predominance of males (70%). All SCD patients were at least 60 days remote from an acute painful vaso-occlusive crisis or blood transfusion and were receiving hydroxyurea. The white cell and absolute neutrophil counts were higher in SCD patients (mean ± SD 8.77 ± 1.52 and 5.07 ± 1.78 x 10 9/L) when compared with controls (mean ± SD 5.33 ± 1.05 and 2.8 ± 0.95 x 10 9/L). Subsequent data are presented as median percentages with interquartile ranges (IQR). A subgroup of the study population demonstrated spontaneous NETosis (27%; SS = 4; AA = 4) and were therefore excluded from our analysis. Contrary to expectations, SCD patients exhibited a lower percentage of NETosis at baseline compared to controls (20 % (11, 36) vs. 33 % (15, 58); p=0.22). Similarly, neutrophils from SCD patients exhibited lower agonist-induced NETosis compared to controls (42% (19, 47) vs. 51% (37, 70); p=0.15) (Fig 1 A and B) Pretreatment of neutrophils from SCD patients with Quercetin appeared to inhibit basal levels of NETosis (6%, (2, 26) vs. 20% (11, 36) p=0.08) although this effect was not appreciable in controls (33% (11, 58) vs. 33% (15, 58) p=0.41) (Fig 1 C and D). Neutrophils from SCD patients that were pretreated with Quercetin and then stimulated with fMLP demonstrated significantly reduced NETosis compared to untreated neutrophils (17.1% (10, 38) vs 41.7% (19, 47) p=0.007) although this effect was not significant in controls (35% (17, 72) vs 50.7% (37, 70) p=0.11) Fig 1 E and F. Our ongoing experiments will demonstrate the effects of more specific inhibitors of neutrophil activation (e.g. R406) in human and mouse models of SCD. Conclusion: These preliminary data suggest lowered NETosis in SCD patients despite neutrophil activation in the systemic inflammatory environment that are partially explained by hydroxyurea treatment. The results also support further evaluation of anti-inflammatory therapies to reduce neutrophil activation in SCD and ameliorate thrombo-inflammatory disease pathology. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Storage lesion–induced, red cell–derived microvesicles (RBC-MVs) propagate coagulation by supporting the assembly of the prothrombinase complex. It has also been reported that RBC-MVs initiate coagulation via the intrinsic pathway. To elucidate the mechanism(s) of RBC-MV–induced coagulation activation, the ability of storage lesion–induced RBC-MVs to activate each zymogen of the intrinsic pathway was assessed in a buffer system. Simultaneously, the thrombin generation (TG) assay was used to assess their ability to initiate coagulation in plasma. RBC-MVs directly activated factor XII (FXII) or prekallikrein, but not FXI or FIX. RBC-MVs initiated TG in normal pooled plasma and in FXII- or FXI-deficient plasma, but not in FIX-deficient plasma, suggesting an alternate pathway that bypasses both FXII and FXI. Interestingly, RBC-MVs generated FIXa in a prekallikrein-dependent manner. Similarly, purified kallikrein activated FIX in buffer and initiated TG in normal pooled plasma, as well as FXII- or FXI-deficient plasma, but not FIX-deficient plasma. Dual inhibition of FXIIa by corn trypsin inhibitor and kallikrein by soybean trypsin inhibitor was necessary for abolishing RBC-MV–induced TG in normal pooled plasma, whereas kallikrein inhibition alone was sufficient to abolish TG in FXII- or FXI-deficient plasma. Heating RBC-MVs at 60°C for 15 minutes or pretreatment with trypsin abolished TG, suggesting the presence of MV-associated proteins that are essential for contact activation. In summary, RBC-MVs activate both FXII and prekallikrein, leading to FIX activation by 2 independent pathways: the classic FXIIa-FXI-FIX pathway and direct kallikrein activation of FIX. These data suggest novel mechanisms by which RBC transfusion mediates inflammatory and/or thrombotic outcomes.

Wound healing is a complex process that consists of multiple phases, each of which are indispensable for adequate repair. Timely initiation and resolution of each of these phases namely, hemostasis, inflammation, proliferation and tissue remodeling, is critical for promoting healing and avoiding excess scar formation. While platelets have long been known to influence the healing process, other components of blood particularly coagulation factors and the fibrinolytic system also contribute to efficient wound repair. This review aims to summarize our current understanding of the role of platelets, the coagulation and fibrinolytic systems in cutaneous wound healing, with a focus on how these components communicate with immune and non-immune cells in the wound microenvironment. We also outline current and potential therapeutic strategies to improve the management of chronic, non-healing wounds.

Background Platelet polyphosphate is an inorganic procoagulant polymer of orthophosphate units that is stored in dense granules and is released upon platelet activation. Here, we describe an assay to measure polyphosphate on the surface of procoagulant human platelets. Methods and Results Recombinant Escherichia coli-expressed exopolyphosphatase deletion mutant PPX_Δ12 labeled with fluorescent Alexa488 dye was used as a polyphosphate probe in flow cytometry. PPX_Δ12-Alexa488-signal dose-dependently increased with long-chain polyphosphate binding to platelets. In contrast, short-chain polyphosphate that is found in the supernatant of activated platelets, did not bind to the platelet surface. Both exopolyphosphatase treatment and polyphosphate pre-incubation abolished PPX_Δ12-Alexa488 binding to polyphosphate on platelets. Stimulation of platelets with thrombin receptor agonist Trap6, and P2Y12 receptor activator ADP increased polyphosphate accumulation on platelet surfaces and PPX_Δ12-Alexa488 signal in a dose-dependent manner. Conclusion This study indicates that long-chain polyphosphate binds to platelet plasma membranes and presents a promising diagnostic assay to measure this interaction on human platelets in platelet-rich plasma. Future investigations will aim to determine if polyphosphate can be used as a novel biomarker of thrombosis. © 2016 International Clinical Cytometry Society

Cancer is an established risk factor for venous thromboembolism (VTE) and VTE is the second leading cause of death in patients with cancer. The incidence of cancer-related thrombosis is rising and is associated with worse outcomes. Despite our growing understanding on tumor-driven procoagulant mechanisms including cancer-released procoagulant proteases, expression of tissue factor on cancer cells and derived microvesicles, as well as alterations in the extracellular matrix of the cancer cell milieu, anticoagulation therapy in cancer patients has remained challenging. This review comments on a newly discovered cancer-associated procoagulant pathway. Experimental VTE models in mice and studies on patient cancer material revealed that prostate cancer cells and associated exosomes display the inorganic polymer polyphosphate on their plasma membrane. Polyphosphate activates blood coagulation factor XII and initiates thrombus formation via the intrinsic pathway of coagulation. Pharmacologic inhibition of factor XII activity protects mice from VTE and reduces thrombin coagulant activity in plasma of prostate cancer patients. Factor XII inhibitors provide thrombo-protection without impairing hemostatic mechanisms and thus, unlike currently used anticoagulants, do not increase bleeding risk. Interference with the polyphosphate/factor XII pathway may provide the novel opportunity for safe anticoagulation therapy in patients with malignancies.

This chapter describes white blood cells of the peripheral blood: neutrophils, eosinophils, basophils, monocytes, and lymphocyte subsets. It describes their basic physiology and important disease states associated with defects of each of these entities. Each of these cells arises from a common bone marrow myeloid or lymphoid progenitor to differentiate into their unique types.

PURPOSE OF REVIEW. This review describes the contribution of coagulation factor XII (FXII) in sterile inflammation and wound healing with a focus on recently identified roles for zymogen FXII in neutrophil functions. RECENT FINDINGS. Recent studies have identified an important role for FXII in neutrophil trafficking. In particular, following neutrophil activation, autocrine FXII signals through its receptor urokinase plasminogen activator receptor (uPAR) on the neutrophil surface to upregulate neutrophil functions. The sum of these activities leads to neutrophil adhesion, chemotaxis, and neutrophil extracellular (NET) formation. Downregulating FXII-mediated signaling in neutrophils is associated with improved wound healing. SUMMARY. These recent findings add to our understanding of the sophisticated role of FXII in vivo and create new avenues of research for the treatment of chronic inflammatory diseases.

Coagulation factor XII (FXII) deficiency is associated with decreased neutrophil migration, but the mechanisms remain uncharacterized. Here, we examine how FXII contributes to the inflammatory response. In 2 models of sterile inflammation, FXII-deficient mice (F12-/-) had fewer neutrophils recruited than WT mice. We discovered that neutrophils produced a pool of FXII that is functionally distinct from hepatic-derived FXII and contributes to neutrophil trafficking at sites of inflammation. FXII signals in neutrophils through urokinase plasminogen activator receptor-mediated (uPAR-mediated) Akt2 phosphorylation at S474 (pAktS474). Downstream of pAkt2S474, FXII stimulation of neutrophils upregulated surface expression of αMβ2 integrin, increased intracellular calcium, and promoted extracellular DNA release. The sum of these activities contributed to neutrophil cell adhesion, migration, and release of neutrophil extracellular traps in a process called NETosis. Decreased neutrophil signaling in F12-/- mice resulted in less inflammation and faster wound healing. Targeting hepatic F12 with siRNA did not affect neutrophil migration, whereas WT BM transplanted into F12-/- hosts was sufficient to correct the neutrophil migration defect in F12-/- mice and restore wound inflammation. Importantly, these activities were a zymogen FXII function and independent of FXIIa and contact activation, highlighting that FXII has a sophisticated role in vivo that has not been previously appreciated.

Plasma protein factor XII (FXII) activates the procoagulant and proinflammatory contact system that drives both the kallikrein-kinin system and the intrinsic pathway of coagulation. When zymogen FXII comes into contact with negatively charged surfaces, it auto-activates to the serine proteaseactivated FXII (FXIIa). Recently, various in vivo activators of FXII have been identified including heparin, misfolded protein aggregates, polyphosphate and nucleic acids. Murine models have established a central role of FXII in arterial and venous thrombosis. Despite its central function in thrombosis, deficiency in FXII does not impair haemostasis in animals and humans. In a preclinical cardiopulmonary bypass system in large animals, the FXIIa-blocking antibody 3F7 prevented thrombosis; however, in contrast to traditional anticoagulants, bleeding was not increased. In addition to its function in thrombosis, FXIIa initiates formation of the inflammatory mediator bradykinin. This mediator increases vascular leak, causes vasodilation, and induces chemotaxis with implications for septic, anaphylactic and allergic disease states. Therefore, targeting FXIIa appears to be a promising strategy for thromboprotection without associated bleeding risks but with anti-inflammatory properties.

The precise mechanism for reduced thrombosis in prekallikrein null mice (Klkb1(-/-)) is unknown. Klkb1(-/-) mice have delayed carotid artery occlusion times on the rose bengal and ferric chloride thrombosis models. Klkb1(-/-) plasmas have long-activated partial thromboplastin times and defective contact activation-induced thrombin generation that partially corrects upon prolonged incubation. However, in contact activation-induced pulmonary thromboembolism by collagen/epinephrine or long-chain polyphosphate, Klkb1(-/-) mice, unlike F12(-/-) mice, do not have survival advantage. Klkb1(-/-) mice have reduced plasma BK levels and renal B2R mRNA. They also have increased expression of the renal receptor Mas and plasma prostacyclin. Increased prostacyclin is associated with elevated aortic vasculoprotective transcription factors Sirt1 and KLF4. Treatment of Klkb1(-/-) mice with the Mas antagonist A-779, COX-2 inhibitor nimesulide, or Sirt1 inhibitor splitomicin lowers plasma prostacyclin and normalizes arterial thrombosis times. Treatment of normal mice with the Mas agonist AVE0991 reduces thrombosis. Klkb1(-/-) mice have reduced aortic tissue factor (TF) mRNA, antigen, and activity. In sum, Klkb1(-/-) mice have a novel mechanism for thrombosis protection in addition to reduced contact activation. This pathway arises when bradykinin delivery to vasculature is compromised and mediated by increased receptor Mas, prostacyclin, Sirt1, and KLF4, leading to reduced vascular TF.

Essentials ClotChip is a novel microsensor for comprehensive assessment of ex vivo hemostasis. Clinical samples show high sensitivity to detecting the entire hemostatic process. ClotChip readout exhibits distinct information on coagulation factor and platelet abnormalities. ClotChip has potential as a point-of-care platform for comprehensive hemostatic analysis. SUMMARY Background Rapid point-of-care (POC) assessment of hemostasis is clinically important in patients with a variety of coagulation factor and platelet defects who have bleeding disorders. Objective To evaluate a novel dielectric microsensor, termed ClotChip, which is based on the electrical technique of dielectric spectroscopy for rapid, comprehensive assessment of whole blood coagulation. Methods The ClotChip is a three-dimensional, parallel-plate, capacitive sensor integrated into a single-use microfluidic channel with miniscule sample volume (

SummaryCombinations of proinflammatory and procoagulant reactions are the unifying principle for a variety of disorders affecting the cardiovascular system. Factor XII (FXII, Hageman factor) is a plasma protease that initiates the contact system. The biochemistry of the contact system in vitro is well understood; however, its in vivo functions are just beginning to emerge. The current review concentrates on activators and functions of the FXII-driven contact system in vivo. Elucidating its physiologic activities offers the exciting opportunity to develop strategies for the safe interference with both thrombotic and inflammatory diseases.

Host and Tumor Factor XII Drive Ovarian Cancer Maintenance and Progression Introduction . Epithelial ovarian cancer (EOC) is the leading cause of cancer death in women.Effective strategies to treat this disease are lacking due to the complexity of pathways involved and the multitude of cells that contribute to EOC biology. To this end, coagulation factor XII (FXII) and its receptor urokinase plasminogen activator receptor (uPAR) represent very promising therapeutic targets because i) uPAR is overexpressed in more than 90% of ovarian cancer patients, ii) FXII has been shown to be upregulated in the peritoneum of EOC patients and promotes EOC dissemination and iii) FXII-uPAR signal and upregulate key neutrophil functions, recently linked to tumor growth and metastasis. Through analysis of the TCGA ovarian cancer patient cohort, we have found that FXII and uPAR are co-expressed in ovarian tumors and their overexpression is associated with decreased overall survival (Fig 1A-B). Given that FXII and uPAR can be produced by both the EOC tumor and the host, the contribution of each of these compartments which has not been examined to date needs to be explored. Thus, we asked if the FXII-uPAR axis in neutrophils and EOC cells synergistically influences tumor biology. Methods - Results. We utilized a tissue microarray to determine FXII and uPAR expression. Both FXII and uPAR were co-expressed in all major histologic subtypes of EOC tumors but not in normal ovarian epithelium (Fig C-D). We adopted a composite expression score system and found significantly increased expression of FXII and uPAR in high grade tumors compared to low grade (grade 1-2) tumors, independently of tumor subtype and stage (Fig 1C-D). Given prior reports that neutrophils are enriched in the ovarian tumor microenvironment (TME) and our findings that FXII-uPAR are integral to neutrophil activation, tumors were also examined for their neutrophil content. Invariably, as tumor grade advanced, Neutrophil Elastase expression significantly increased (data not shown). We next asked if neutrophils contribute to EOC tumor progression or their recruitment merely correlates with advanced disease. We found that in the presence of neutrophils, EOC cells migrate significantly faster (p Next, in order to assess whether host FXII could contribute to EOC dissemination and progression we utilized WT, F12-/-, and uPAR deficient (Plaur-/-) mice for in vivo EOC tumor model. After orthotopic injection of ID8 EOC cells, WT mice exhibited faster rates of tumor development and ascitic fluid accumulation (13.4 ± 0.92 ml), relative to F12-/- (0.37 ± 0.26 ml) and Plaur-/- (0.5 ± 0.5 ml) mice (Fig 1G). Blinded examination of tumors showed significantly higher tumor burden in WT mice compared to F12-/-and Plaur-/- mice, with F12-/-mice exhibiting the highest degree of protection (Fig 1H). Conclusions . Our studies indicate three novel aspects: i) a direct crosstalk between ovarian cancer cells and neutrophils, that enhances tumor cell migration through FXII-uPAR signaling; ii) the presence of neutrophils in the TME induces EMT of cancer cells which is abolished when the FXII-uPAR interaction is inhibited and; iii) abrogation of the FXII-uPAR axis in EOC tumor cells and neutrophils, synergistically restricts the pro-invasive phenotype of ovarian tumor cells. Disclosures No relevant conflicts of interest to declare.

Bradykinin B2 receptor-deleted mice (Bdkrb2(-/-)) have delayed carotid artery thrombosis times and prolonged tail bleeding time resulting from elevated angiotensin II (AngII) and angiotensin receptor 2 (AT2R) producing increased plasma nitric oxide (NO) and prostacyclin. Bdkrb2(-/-) also have elevated plasma angiotensin-(1-7) and messenger RNA and protein for its receptor Mas. Blockade of Mas with its antagonist A-779 in Bdkrb2(-/-) shortens thrombosis times (58 ± 4 minutes to 38 ± 4 minutes) and bleeding times (170 ± 13 seconds to 88 ± 8 seconds) and lowers plasma nitrate (22 ± 4 μM to 15 ± 5 μM), and 6-keto-PGF1α (259 ± 103 pg/mL to 132 ± 58 pg/mL). Bdkrb2(-/-) platelets express increased NO, guanosine 3',5'-cyclic monophosphate, and cyclic adenosine monophosphate with reduced spreading on collagen, collagen peptide GFOGER, or fibrinogen. In vivo A-779 or combined L-NAME and nimesulide treatment corrects it. Bdkrb2(-/-) platelets have reduced collagen-related peptide-induced integrin α2bβ3 activation and P-selectin expression that are partially corrected by in vivo A-779, nimesulide, or L-NAME. Bone marrow transplantations show that the platelet phenotype and thrombosis time depends on the host rather than donor bone marrow progenitors. Transplantation of wild-type bone marrow into Bdkrb2(-/-) hosts produces platelets with a spreading defect and delayed thrombosis times. In Bdkrb2(-/-), combined AT2R and Mas overexpression produce elevated plasma prostacyclin and NO leading to acquired platelet function defects and thrombosis delay.

Polyphosphate is an inorganic procoagulant polymer. Here we develop specific inhibitors of polyphosphate and show that this strategy confers thromboprotection in a factor XII-dependent manner. Recombinant Escherichia coli exopolyphosphatase (PPX) specifically degrades polyphosphate, while a PPX variant lacking domains 1 and 2 (PPX_Δ12) binds to the polymer without degrading it. Both PPX and PPX_Δ12 interfere with polyphosphate- but not tissue factor- or nucleic acid-driven thrombin formation. Targeting polyphosphate abolishes procoagulant platelet activity in a factor XII-dependent manner, reduces fibrin accumulation and impedes thrombus formation in blood under flow. PPX and PPX_Δ12 infusions in wild-type mice interfere with arterial thrombosis and protect animals from activated platelet-induced venous thromboembolism without increasing bleeding from injury sites. In contrast, targeting polyphosphate does not provide additional protection from thrombosis in factor XII-deficient animals. Our data provide a proof-of-concept approach for combating thrombotic diseases without increased bleeding risk, indicating that polyphosphate drives thrombosis via factor XII., The inorganic procoagulant polymer polyphosphate participates in thrombosis via factor XII. Here the authors use recombinant probes that specifically bind or degrade circulating polyphosphate to protect mice in arterial and venous thrombosis models without an increased bleeding risk, the primary complication of all currently used anticoagulants.

Platelet polyphosphate is an inorganic procoagulant polymer of orthophosphate units that is stored in dense granules and is released upon platelet activation. Here, we describe an assay to measure polyphosphate on the surface of procoagulant human platelets.Recombinant Escherichia coli-expressed exopolyphosphatase deletion mutant PPX_Δ12 labeled with fluorescent Alexa488 dye was used as a polyphosphate probe in flow cytometry. PPX_Δ12-Alexa488-signal dose-dependently increased with long-chain polyphosphate binding to platelets. In contrast, short-chain polyphosphate that is found in the supernatant of activated platelets, did not bind to the platelet surface. Both exopolyphosphatase treatment and polyphosphate pre-incubation abolished PPX_Δ12-Alexa488 binding to polyphosphate on platelets. Stimulation of platelets with thrombin receptor agonist Trap6, and P2YThis study indicates that long-chain polyphosphate binds to platelet plasma membranes and presents a promising diagnostic assay to measure this interaction on human platelets in platelet-rich plasma. Future investigations will aim to determine if polyphosphate can be used as a novel biomarker of thrombosis. © 2016 International Clinical Cytometry Society.

Plasma kallikrein formed from prekallikrein (PK) produces bradykinin from kininogens and activates factor XII. Plasma PK is activated by factors αXIIa, βXIIa, or prolylcarboxypeptidase (PRCP). A cross-sectional investigation determined if there is an association of PRCP and KLKB1 polymorphisms with cardiovascular disease (CVD). DNA was obtained from 2243 individuals from the Prevention of Events with Angiotensin Converting Enzyme trial. Two PRCP SNPs, rs7104980 and rs2298668, and two KLKB1 SNPs, rs3733402 and rs3087505, were genotyped. Logistic regression models were performed for history of diabetes, myocardial infarction, stroke, angina, angiographic coronary disease, CABG, intermittent claudication, percutaneous transluminal coronary angioplasty (PTCA), and transient ischemic attack. The PRCP SNP rs7104980 increased the odds of having a history of PTCA by 21% [odds ratio (OR) = 1.211; 95% confidence intervals (CI) = (1.008, 1.454)]; P = 0.041, but was non-significant after Bonferroni correction. Alternatively, having the G allele for rs3733402 (KLKB1 gene) decreased the odds of having a history of angiographic coronary disease by 24% [OR = 0.759; 95% CI = (0.622, 0.927)]; P = 0.007 that was statistically significant (P

Introduction: Direct oral anticoagulants (DOACs) are a new class of medications that have been designed to provide direct inhibition of either coagulation factor IIa (FIIa, dabigatran) or FXa (rivaroxaban, apixaban, and edoxaban) and are rapidly replacing warfarin as the anticoagulant-of-choice for the treatment of most thrombotic disorders and atrial fibrillation. These newer agents present several advantages including predictable pharmacokinetic profile, wide therapeutic window, and shorter half-life. Despite these advantages, metabolism of DOACs is complex and requires enteric absorption and liver or renal clearance. Thus, the pervading maxim that DOACs do not require laboratory monitoring is simplistic and there are several situations in which assessment of the anticoagulant effect of DOACs will be useful. Indications for assessment of DOAC effects on the coagulation system include need for emergent surgery, unexpected thrombotic or hemorrhagic events, patients with extreme body weight, abrupt impairment of liver and kidney function, suspicion of DOAC overdose, poor compliance, or after administration of reversal agents. To date, no assays developed to measure DOAC activity have been approved by the Food and Drug Administration (FDA). Thus, there is an unmet need for a rapid coagulation assay that can measure the anticoagulant effect of DOACs in the laboratory or at the POC. We have recently developed a novel dielectric microsensor, termed ClotChip, that allows for the comprehensive assessment of blood hemostasis using a disposable microfluidic sensor at the POC (Fig 1A). The aim of this study was to assess the clinical utility of ClotChip at measuring the anticoagulant effects of DOACs in whole blood. Methods: We conducted a pilot clinical study at the Louis Stokes Cleveland VA Medical Center and accrued 127 individuals after IRB approval. Of these, 47 were healthy volunteers (not taking any anticoagulation or antiplatelet therapy) and the remaining participants were patients on DOACs (rivaroxaban: n=25, apixaban: n=47, dabigatran: n=8). Whole blood samples were collected in 3.2% sodium citrate. Samples from patients on DOACs were collected within 6 hours of rivaroxaban ingestion, between 3 - 5 hours post-morning dose of apixaban, or within 12 hours of dabigatran intake. All samples underwent whole blood measurement with ClotChip within 4 hours of collection as well as conventional plasma-based coagulation tests including PT, aPTT, drug specific anti-Xa assays or dilute thrombin time. The ClotChip is based on the electrical technique of dielectric spectroscopy (DS) to monitor the hemostatic process ex vivo in a low-cost (material cost < $1), small-sized (26mm × 9mm × 3mm), and disposable microfluidic sensor with miniscule sample volume (< 10µL). The ClotChip readout was taken as the temporal variation in the real part of blood dielectric permittivity at 1 MHz. The time to reach a peak in permittivity (Tpeak), is a sensitive parameter to assess coagulation defects, and we hypothesized that Tpeakcan effectively measure the anticoagulant effect of DOACs (Fig. 1B). Results: Using Gaussian fit method, mean Tpeakfor the control group was determined to be 429 sec (239 - 619 sec, ±2 SD, Fig 1C). There was statistically significant prolongation in Tpeakfor rivaroxaban (637 ± 24 sec., mean ± SEM, p < 0.0001), apixaban (593 ± 23 sec, mean ± SEM, p < 0.0001) and dabigatran (894 ± 82 sec, mean ± SEM, p < 0.0001) samples (Fig 1C). An ROC curve was then generated using statistical software to determine the true positive rate (sensitivity) and false positive rate (100% - specificity). The area under the curve (AUC) for ClotChip Tpeakwas 0.9185 for rivaroxaban, 0.8132 for apixaban and 1 for dabigatran (Fig 1D). Conclusions: There are currently no approved laboratory assays that reliably measure the anticoagulant effect of DOACs. ClotChip offers a portable POC platform for rapid, comprehensive assessment of hemostasis using a miniscule amount of whole blood ( Disclosures Maji: Case Western Reserve University: Patents & Royalties: Licensed to XaTek, Inc. . Mohseni:Case Western Reserve University: Patents & Royalties: Licensed to XaTek, Inc.; XaTek, Inc.: Consultancy. Suster:XaTek, Inc.: Consultancy; Case Western Reserve University: Patents & Royalties: licensed to XaTek, Inc..

Management of immune thrombocytopenia in pregnancy can be a complex and challenging task and may be complicated by fetal-neonatal thrombocytopenia. Although fetal intracranial hemorrhage is a rare complication of immune thrombocytopenia in pregnancy, invasive studies designed to determine the fetal platelet count before delivery are associated with greater risk than that of fetal intracranial hemorrhage and are discouraged. Moreover, the risk of neonatal bleeding complications does not correlate with the mode of delivery, and cesarean section should be reserved only for obstetric indications.

The plasma protein factor XII (FXII) is the initiating protease of the procoagulant and proinflammatory contact system. FXII activates both the bradykinin (BK) producing kallikrein-kinin system and the intrinsic pathway of coagulation. Contact with negatively charged surfaces induces auto-activation of zymogen FXII that results in activated FXII (FXIIa). Various in vivo activators of FXII have been identified including heparin, misfolded protein aggregates, nucleic acids and polyphosphate. Murine models have established a central role of FXII in arterial and venous thromboembolic diseases. Despite the central function of FXII in pathologic thrombosis, its deficiency does not impair hemostasis in animals or humans. The selective role of FXIIa in thrombosis, but not hemostasis, offers an exciting novel strategy for safe anticoagulation based on interference with FXIIa. We have generated the recombinant fully human FXIIa-blocking antibody 3F7, which abolished FXIIa enzymatic activity and prevented thrombosis in a cardiopulmonary bypass system in large animals, in the absence of increased therapy-associated bleeding. Furthermore, 3F7 also interfered with BK-driven edema in the severe swelling disorder hereditary angioedema (HAE) type III. Taken together, targeting FXIIa with 3F7 appears to be a promising approach to treat edema disorders and thrombosis.

This paper reports on the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy (DS) of human whole blood during coagulation. The sensor employs a three-dimensional (3D), parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Using an impedance analyzer and after a 5-point calibration, the sensor is shown to measure the real part of complex relative dielectric permittivity of human whole blood in a frequency range of 10kHz to 100MHz. The temporal variation of dielectric permittivity at 1MHz for human whole blood from three different healthy donors shows a peak in permittivity at ∼ 4 to 5 minutes, which also corresponds to the onset of CaCl 2 -initiated coagulation of the blood sample verified visually.

Cancer is a leading cause of thrombosis. We identify a new procoagulant mechanism that contributes to thromboembolism in prostate cancer and allows for safe anticoagulation therapy development. Prostate cancer-mediated procoagulant activity was reduced in plasma in the absence of factor XII or its substrate of the intrinsic coagulation pathway factor XI. Prostate cancer cells and secreted prostasomes expose long chain polyphosphate on their surface that colocalized with active factor XII and initiated coagulation in a factor XII-dependent manner. Polyphosphate content correlated with the procoagulant activity of prostasomes. Inherited deficiency in factor XI or XII or high-molecular-weight kininogen, but not plasma kallikrein, protected mice from prostasome-induced lethal pulmonary embolism. Targeting polyphosphate or factor XII conferred resistance to prostate cancer-driven thrombosis in mice, without increasing bleeding. Inhibition of factor XII with recombinant 3F7 antibody reduced the increased prostasome-mediated procoagulant activity in patient plasma. The data illustrate a critical role for polyphosphate/factor XII-triggered coagulation in prostate cancer-associated thrombosis with implications for anticoagulation without therapy-associated bleeding in malignancies.

Hageman trait refers to an inherited deficiency of coagulation factor XII (FXII). The term was named by Oscar Ratnoff in 1955 after the index patient John Hageman, who had ‘incoagulable’ blood in vitro but no abnormal bleeding even after surgeries [1, 2]. Subsequently, Earl Davie and Oscar Ratnoff isolated Hageman factor, the protein missing in Hageman’s blood, which later was called FXII [3, 4]. This pioneer work contributed to the ‘Waterfall/Cascade’ hypothesis of blood coagulation presented in 1964 [5, 6], which established the basic principle that blood coagulation is mediated by the sequential activation of a series of plasma proteases. John Hageman died of pulmonary thromboembolism during bed rest from a broken hip in 1968 before gene cloning techniques were available [7]. As a result, the genetic defect underlying his FXII-deficiency was never determined. In this study, we obtained blood samples from descendants of the Hageman family to analyze their F12 gene that encodes FXII. The study was approved by the Cleveland Clinic Institutional Review Board. All participants provided written consent. John Hageman was never married and had no known descendants (Fig. 1A). We obtained blood samples from III-1, III-3-5 and IV-3-5, who were family members of his siblings’ descendants. None of these individuals had a history of abnormal bleeding. PCR and DNA sequencing of all 14 F12 gene exons in these individuals found no deletion, insertion or non-synonymous point mutations. In III-3 and IV-5, however, a G→A intronic mutation was identified at nucleotide position 11396 of the F12 gene [8] (Fig. 1B), which was part of the splice acceptor site of exon 14 (Fig. 1C). The mutation abolished the original splice acceptor site and created a new site one nucleotide downstream. As a result, the exon 14 reading frame was shifted by one position, thereby encoding a new peptide that replaced the catalytic serine and the rest of the protease domain (Fig. 1C). Fig. 1 (A) Hageman family pedigree. The pedigree was modified for confidentiality. J.H., John Hageman. Diamonds with a slash line represent deceased individuals. Diamonds with a dot represent heterozygous carriers. IV-1–2 were not available for the study. ... Interestingly, this 11396(G→A) mutation was reported previously in FXII-deficient individuals in Germany [9, 10]. PCR analysis of transcripts from the mutant F12 gene confirmed the predicted fusion mRNA. The study also showed that the fusion protein, if translated from the fusion mRNA, was unstable, because individuals homozygous for this mutation had no detectable plasma FXII antigen or activity [9, 10]. By ELISA (Innovative Research Inc.), we found that plasma FXII antigen levels in III-3 and IV-5, who were heterozygous for the mutation, were ~50% of that in other members of the family (Fig. 1A). The antigen level in the normal individuals of this family was ~1.8 fold higher than that of pooled normal plasma. The levels in III-3 and IV-5 were at ~90% of pooled normal plasma level (data not shown). As measured by a modified one-stage activated partial thromboplastin time, plasma FXII coagulant activity in four family members (III-1 and IV-3-5), whose blood was collected in sodium citrate, were 1.31, 1.44, 1.28 and 1.21 U/mL, respectively. On immunoblots, plasma FXII protein in all samples had a similar molecular mass, although the level in samples from III-3 and IV-5 was lower (data not shown). No additional FXII protein bands were detected on immunoblots. The data were consistent with the genotype in these individuals. These studies identified an F12 gene mutation in the descendants of the Hageman family. We showed that there was a mutant allele in III-3 and IV-5, which was likely from II-3 who inherited it from I-1 or I-2. It is likely that John Hageman (II-1) also inherited this mutant allele. Given the fact that there was no detectable FXII activity in his blood [2], John Hageman was expected to be either homozygous for this mutant allele or compounded heterozygous with another unknown mutant F12 allele. An inquiry of family history indicated no evidence that his parents were consanguineous but revealed that they emigrated from the central part of Germany, where the same mutant F12 allele was reported in at least five unrelated families [9, 10]. This mutant allele also existed in another unrelated family in Switzerland [10]. All of the individuals with this allele were asymptomatic and identified only by chance during hospital visits. Apparently, this mutation originated for sometime in history and is present in a number of individuals in Europe, especially in Germany. Since no other F12 mutations were found in the descendents of his family, the possibility cannot be excluded that John Hageman may have inherited two copies of the same mutant F12 allele from his parents. The chance encounter of John Hageman by Oscar Ratnoff more than half a century ago had a major role in the history of understanding the blood coagulation system [1, 3, 11–14]. Now FXII is known to be important in the contact activation system to regulate blood pressure, vascular permeability, complement activation, inflammatory responses, angiogenesis, and thrombosis risk [15–17]. Our finding of the F12 gene mutation in the Hageman family, providing an explanation to the long-standing question of John Hageman’s genetic defects, adds a fresh footnote to this important history in hematology.