scholarly journals Inhibition of Factor XII Attenuates Prothrombotic Complications in Sickle Cell Mice

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 189-189
Author(s):  
Erica Sparkenbaugh ◽  
Christina M Abrams ◽  
Megan D Miller ◽  
Brian C Cooley ◽  
Anton Ilich ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Ischemic Stroke ◽  
Venous Thrombosis ◽  
Research Funding ◽  
Femoral Vein ◽  
Factor Xii ◽  
Male And Female ◽  
Trial Investigator ◽  
Adherent Leukocytes ◽  
Coagulation Pathway

Abstract Sickle Cell Disease (SCD) is the most common inherited hemoglobinopathy, affecting millions worldwide. Although characterized by chronic hemolytic anemia and recurrent vaso-occlusive episodes, SCD is increasingly recognized as a hypercoagulable state. Indeed, SCD patients have an 11-25% incidence of venous thromboembolism at a median age of 30 years, associated with a 3-fold increased risk of mortality. Moreover, ischemic stroke and silent cerebral infarctions occur in 7-13% of SCD patients. We have previously shown that tissue factor, an initiator of the extrinsic coagulation pathway, contributes to thrombo-inflammation and microvascular cerebral thrombosis in mouse models of SCD . Recently, the intrinsic coagulation pathway, including Factor XII (FXII), has received significant attention because targeting components of this pathway reduces thrombosis without affecting primary hemostasis. We have shown that FXII deficiency reduces plasma markers of thrombin generation and inflammation in sickle mice. However, the contribution of FXII to thrombosis and prothrombotic complications in SCD is not known. In this study we evaluated the effects of blocking FXII activity on venous thrombosis and ischemia/reperfusion (IR)-induced brain injury in SCD mice. First, Townes HbSS mice (SS) and non-sickle Townes HbAA controls (AA) (male and female, 16 weeks) received anti-FXII antibody or control IgGκ1 (10 mg/kg, IV) 30 minutes prior to subjecting them to venous thrombosis, initiated by applying positive current (3 volts, 90 sec) to the femoral vein. To visualize platelet and fibrin accumulation, mice were injected with rhodamine 6G and anti-fibrin antibody 59D8 labeled with Alexa Fluor 647, respectively. The femoral vein thrombi were imaged by intravital fluorescence microscopy using time-lapse capture every 10 seconds, to acquire images of fibrin and platelets over 60 min. The accumulation of platelets and fibrin was quantified for relative intensity of each fluorophore over the region of the observed thrombus. As previously shown, thrombi of SS/IgG mice showed an increased fibrin and platelet accumulation compared to AA/IgG group. Importantly, 15D10 treatment significantly attenuated both fibrin (p<0.001) and platelet (p<0.05) deposition over time in SS mice compared to SS/IgG group. The same effect of 15D10 treatment was observed in AA mice. At the end of experiment, clots were collected and stained with hematoxylin and eosin, and clot volume was assessed histomorphometrically (Nikon Ti-2, FIJI Software). Surprisingly, despite higher fibrin content, clots from SS/IgG mice had significantly smaller volume than clots from AA/IgG group (0.32 ± 0.04 versus 0.60 ± 0.11 mm 3, p<0.05). Importantly, administration of 15D10 significantly reduced clot volume in both SS (0.086 ± 0.01 mm 3, p<0.05) and AA mice (0.1 ± 0.02 mm 3, p<0.05). Next, AA and SS mice (male and female, 8-10 weeks) were subjected to brain IR injury induced by middle cerebral artery occlusion for 60 minutes followed by 24 hours of reperfusion (mouse model of ischemic stroke). 15D10 or control IgGκ1 (10 mg/kg, IV) were injected 30 minutes before occlusion and again at 6 hours into the reperfusion period to generate 3 experimental groups: AA/IgG, SS/IgG and SS/15D10. All analyzed parameters of brain IR injury were significantly worse in the SS/IgG group compared to the AA/IgG group. Compared to IgG, pre-treatment of SS mice with 15D10 significantly attenuated neuronal damage determined by volume of brain infarction (11.7 ± 3.7 vs 24.9 ± 2.4%, p<0.001) and improved behavioral deficit assessed by mean stroke score (9.0 ± 0.9 vs 14.6 ± 0.9, p<0.01). These changes were accompanied by a significant increase in leukocytes rolling (1978.0 ± 93.5 vs 1517.0 ± 180.3 rolling leukocytes/sec/mm 2, p<0.001), and significant reduction in the number of adherent leukocytes (367.2 ± 49.0 vs 723.4 ± 48.5, adherent leukocytes/mm 2, p<0.001) observed in the brain microvasculature of SS mice treated with 15D10 compared to SS/IgG group. Together, our data indicates that in the mouse model of SCD FXII contributes to the experimental venous thrombosis and ischemic stroke. Given that targeting the intrinsic pathway can reduce thrombosis without affecting hemostasis, our data suggest that targeting FXII might be a beneficial treatment in reducing inflammatory and thrombotic complications in SCD patients without a risk of bleeding. Disclosures Wallisch: Aronora Inc,: Current Employment. Key: Grifols: Research Funding; Takeda: Research Funding; BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Sanofi: Consultancy; Uniqure: Consultancy, Other: Participation as a clinical trial investigator. Gruber: Aronora Inc.: Current Employment, Current equity holder in publicly-traded company; Oregon Health and Science University: Current Employment.

scholarly journals Emizicumab Promotes Factor Xa Generation on Activated Endothelium in a Blood Cell-Independent Manner

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3182-3182
Author(s):  
Patrick Ellsworth ◽  
Dougald Monroe ◽  
Maureane Hoffman ◽  
Nigel S Key
Keyword(s):  
Clinical Trial ◽  
Endothelial Cells ◽  
Growth Medium ◽  
Research Funding ◽  
Hemophilia A ◽  
Coagulation Factor ◽  
Standard Of Care ◽  
Factor Ix ◽  
Adhesive Film ◽  
Trial Investigator

Abstract Introduction Hemophilia A (HA) is an inherited bleeding disorder caused by the deficiency of coagulation factor VIII (FVIII) resulting in severe hemorrhage if untreated. Recombinant and plasma derived FVIII products have long been the standard of care in hemophilia. However, approximately 25-30% of patients with severe HA develop inhibitors, neutralizing alloantibodies to FVIII, a significant complication in the treatment of patients with HA that leads to bleeding despite factor therapy. First approved for bleed prophylaxis in HA with inhibitors in the US by the FDA in 2018, emicizumab (Genentech, USA) has initiated a new era of HA treatment. This drug is a bispecific, monoclonal antibody that binds to activated Factor IX (FIXa) and Factor X (FX), mimicking activated FVIII (FVIIIa) by bringing FIXa and FX into proximity to enable FX activation, even in the presence of inhibitors. Emicizumab prophylaxis drastically reduces bleed episodes. However, thromboses and thrombotic microangiopathy (TMA) were observed in trials, all associated with concomitant use of activated prothrombin complex concentrates (aPCC) (Callaghan et al., 2021). The mechanism of this devastating condition is uncertain, as emicizumab is not known to bind to phospholipid or vascular surfaces. We report that FX is more readily activated by FIXa and emicizumab on endothelium that has been activated by tumor necrosis factor alpha (TNF). This finding may partially explain the development of TMA in these patients. Methods We utilized novel, microfluidic devices that are inexpensive to manufacture and were modified from a technique previously described (Alapan et al. 2016). These devices are fabricated using a laser cut double-sided adhesive film sandwiched between a clear, gas-permeable polymer (Ibidi, Germany) and an acrylic top that is laser cut (Universal Laser Systems Inc., USA) (Figure 1). Human umbilical endothelial cells (HUVEC, Lonza, Switzerland) were harvested at passage 3 to 4 and seeded into the devices. These were then cultured under flow conditions using a non-peristaltic, air-driven pump (Ibidi GmbH, Germany) to achieve a confluent and quiescent endothelial surface. HUVEC are then activated by incubating with 5 nM TNF in serum-free growth medium for 4 hours. This treatment induced markers of endothelial activation without gross apoptosis. Non-activated HUVEC were incubated with endothelial cell growth medium (2% serum) until time of experiments. Factors IXa, X (Haemtech, USA), and/or emicizumab (discarded clinical material) were mixed in HEPES-buffered saline with 5 mM calcium chloride for all experimental conditions. Concentrations used of FIXa (30 nM), FX (170 nM), and emicizumab (55 ug/mL) were constant for all conditions. Combinations of factors and emicizumab were then incubated in the endothelialized device for 30 minutes at 37° C. The entire volume of the mixture was then aspirated (20 uL) and stored at -80° C. FXa activity was assayed on the effluent for 60 minutes using a chromogenic FXa substrate (Pefachrome, Pentapharm, Switzerland). Results No significant generation of Xa was noted in the presence of healthy or activated endothelium with emicuzumab alone, emicizumab and FIXa, emicizumab and FX, or factors IXa and X. Median Xa generation observed with the combination of emicizumab, FIXa, and FX on healthy endothelium was 2 nM. Median Xa generation with the same combination on activated endothelium was 8.1 nM, a four-fold increase (P = 0.028, Mann-Whitney test) (Figure 2). Discussion Emicizumab represents an evolving standard of care for hemophilia A. Considering data showing diminishing FVIII expression in the months to years after AAV gene therapy, (Pasi et al., 2020) it may well be the dominant treatment paradigm in HA for some time. However, much remains to be answered in the use of emicizumab, and the mechanism of thrombosis and TMA with concomitant aPCC use has resulted in the avoidance of aPCC use for breakthrough bleeding in patients on emicizumab therapy, even up to 6 months after cessation. Our data demonstrate that activated endothelial cells promote FX activation more readily than quiescent endothelial cells in the presence of FIXa and emicizumab. These findings demonstrate the potential of thrombotic angiopathy in an in vitro system. Further investigation of the interaction of endothelium with FIXa, FX, and FVIIIa-mimetic antibodies is warranted. Figure 1 Figure 1. Disclosures Ellsworth: Takeda: Other: Salary supported as part of NHF-Takeda Clinical Fellowship Award. Monroe: Medexus Pharmaceuticals: Consultancy; Takeda: Consultancy; Otello Medical: Current equity holder in publicly-traded company. Hoffman: Takeda: Research Funding; CSL Behring: Consultancy; Sanofi: Consultancy; BPL (Bio Products Laboratory): Consultancy. Key: BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Takeda: Research Funding; Grifols: Research Funding; Uniqure: Consultancy, Other: Participation as a clinical trial investigator; Sanofi: Consultancy.

scholarly journals Rituximab Monotherapy Is Effective for Inhibitor Eradication with Concomitant Porcine Factor VIII Followed By Emicizumab for Bleed Control in Acquired Hemophilia a

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 348-348
Author(s):  
Patrick Ellsworth ◽  
Sheh-Li Chen ◽  
Christopher Wang ◽  
Nigel S Key ◽  
Alice Ma
Keyword(s):  
Clinical Trial ◽  
Factor Viii ◽  
Research Funding ◽  
Hemophilia A ◽  
Effective Strategy ◽  
Acquired Hemophilia A ◽  
Acquired Hemophilia ◽  
Trial Investigator ◽  
Fviii Activity ◽  
Inhibitor Titer

Abstract Introduction Acquired hemophilia A (AHA) is a rare bleeding disorder in which acquired auto-antibodies to endogenous Factor VIII (FVIII) resulting in decreased FVIII activity. AHA can lead to life-threatening bleeding, with effective treatment requiring both immunosuppressive therapy (IST) and bypassing agents such as recombinant activated Factor VII (rFVIIa) or activated prothrombin complex concentrates (APCC) (Tiede et al. Haematologica 2020). Some, including our group, have begun using emicizumab as well (Knoebl et al. Blood 2020). IST is required for inhibitor eradication, but regimens are heterogenous and have not been systematically compared in the literature. While there is no standard of care IST in these patients, most patients in the literature receive multiple agents, including corticosteroids, mycophenolate mofetil, cyclosporine, and/or rituximab in combination. We report in a prospective cohort that for IST, rituximab monotherapy is an effective strategy. An updated treatment algorithm is offered that has been effective for treatment of these patients at our institution, which adds emicizumab therapy after initial bleed control. Methods We analyzed clinical, pharmacy, and laboratory data from 24 patients treated with rpFVIII at the University of North Carolina for AHA from July 2015 to June 2021. All patients were initially treated according to our previously established dosing algorithm with recombinant porcine FVIII, and the last five patients have received emicizumab after initial factor dosing (see Figure 1). 17 of the patients who received rituximab and were followed at our center subsequently attained inhibitor eradication, six of those received only rituximab therapy. Investigational review board approval was obtained for our data collection and analysis. Patients who did not receive rituximab, failed to reach an inhibitor level <0.5 BU, or who were lost to follow up were excluded from the analysis. For patients that fit the inclusion criteria, the time between date of the first rituximab infusion and the date of inhibitor eradication was calculated. Results All patients in our cohort who we followed until inhibitor eradication (17 of 24 patients) had eradication of inhibitors after a median of 143 days from initiation of immunosuppression. For patients treated with rituximab monotherapy for inhibitor eradication (6 of 17), this goal was reached in a median of 134.5 days (range 76-191 days). For those who received agents in addition to rituximab and have reached inhibitor eradication to date (9 of 17 patients), median days from initiation of immunosuppression to inhibitor eradication was 137.5 days (range 11-485) (P = 0.43 on Mann-Whitney test). Patients were treated as previously reported by our group per an algorithm that starts recombinant porcine FVIII without waiting for a porcine inhibitor and at lower than FDA recommended dosing. Subsequent doses for bleed control are titrated according to one-stage, clot based FVIII activity. This report also includes 5 new patients who, after initial bleed control per our algorithm, were initiated on emicizumab while awaiting inhibitor eradication. There was no correlation between time to rituximab initiation and time to inhibitor eradication in both those who received rituximab monotherapy and those who had multiple IST agents. There was also no significant difference in initial inhibitor titer between groups with median initial inhibitor titer of 104 BU in the rituximab monotherapy group, and 70 BU in the multiple IST agents group (see Figure 3). Conclusions Rituximab monotherapy appears to be an effective strategy for inhibitor eradication in acquired hemophilia A. In the context of bleed treatment with porcine factor, followed by emicizumab, a standardized, algorithmic approach can be effectively employed for these patients. Though any patients have inhibitor recurrence, as is described in the literature, with emicizumab available, bleeding can be avoided with regular monitoring. Emicizumab given while re-eradicating an inhibitor can prevent morbidity of this disease. Figure 1 Figure 1. Disclosures Ellsworth: Takeda: Other: Salary supported as part of NHF-Takeda Clinical Fellowship Award. Key: Uniqure: Consultancy, Other: Participation as a clinical trial investigator; Grifols: Research Funding; Takeda: Research Funding; BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Sanofi: Consultancy. Ma: Accordant: Consultancy; Takeda: Honoraria, Research Funding. OffLabel Disclosure: Emicizumab is not approved for use in Acquired Hemophilia A and this represents an OFF LABEL use of the drug.

scholarly journals The Impact of Electrical Calf Muscle Stimulation on the Residual Venous Obstruction and DVT Recurrence after Cessation of Standard Anticoagulation

Blood ◽  
2017 ◽  
Vol 130 (Suppl_1) ◽  
pp. 698-698
Author(s):  
Kirill Lobastov ◽  
Vladimir Ryzhkin ◽  
Athena Vorontsova ◽  
Iliya Schastlivtsev ◽  
Victor Barinov ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Research Funding ◽  
Femoral Vein ◽  
Main Group ◽  
Calf Muscle ◽  
Popliteal Vein ◽  
Control Group ◽  
Muscle Stimulation ◽  
Venous Obstruction ◽  
The Impact

Abstract Aim. To assess the efficacy of electrical calf muscle stimulation (EMS) in patients with post-thrombotic syndrome (PTS) and residual venous obstruction (RVO) after cessation of a standard anticoagulation. Methods. This was a prospective comparative clinical trial with masked outcome assessor involving patients after the first episode of unprovoked femoro-popliteal DVT who have completed a standard 6-month course of anticoagulation and had signs of RVO in the affected veins and Villalta score of 5 and more. Totally were enrolled 60 patients in the age of 40-86 years (mean - 58,5 ± 11,4), 38 men and 22 women, divided into two groups of 30 participants. In both groups (main and control) PTS was treated by active walking (at least 5,000 steps per day controlled by an individual pedometer), below-knee graduated compression stockings (23-32 mm Hg) and micronized purified flavonoid fraction (2-month course twice a year). In the main group, EMS with «Veinoplus VI» device (3 procedures of 30 minutes every day) also was used. The main endpoint of the study was symptomatic or asymptomatic recurrent venous thrombosis confirmed by duplex ultrasound (DUS). The additional criteria of treatment efficacy were changes in the degree of current venous stenosis. The patients were followed up for 12 months with monthly DUS, aimed to reveal recurrent DVT, and 6-monthly DUS with evaluation of stenosis degree. Results. RVO was represented by an average of 48%-stenosis of the common femoral vein in 12 patients, 53%-stenosis of the superficial femoral vein in 16 cases and 55%-stenosis of the popliteal vein in all participants. Through 12-month follow up the degree of stenosis decreased in all affected veins in both groups (p<0,05). The most vivid dynamics was found in the popliteal vein: 60.8% - 55.1% - 28.8% in the main group and 50.9% - 30.1% - 27.3% in the control group (p<0,0001) with significant differences between the groups (p=0.004) Recurrence of venous thrombosis was found in 7 of 30 patients in the control group and in 0 of 30 patients in the main group (23.3% vs 0%, p=0.011). In 5 cases the recurrent DVT was silent and revealed by regular DUS and only in 2 cases it had a clinical manifestation. 4 of 5 silent cases were presented with re-occlusion of the early affected vein. Conclusions. There is an ongoing process of deep veins recanalization during 12 months after cessation of anticoagulation in patients with RVO and PTS. Using of EMS in complex treatment of PTS allows to reduce the rate of recurrent DVT and increase the speed of recanalization. Disclosures Lobastov: "Gemakor Labs" Ltd: Honoraria, Research Funding; "BEHO+" Ltd: Honoraria, Research Funding. Ryzhkin: "BEHO+" Ltd: Research Funding. Laberko: "Gemakor Labs" Ltd: Honoraria, Research Funding; "BEHO+" Ltd: Honoraria. Rodoman: "Gemakor Labs" Ltd: Research Funding.

scholarly journals Coagulation Factor XI and Factor XII in DNA-Induced Thrombin Generation

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 581-581 ◽  
Author(s):  
Anton Matafonov ◽  
Ivan S. Ivanov ◽  
Mao-fu Sun ◽  
David Gailani
Keyword(s):  
Venous Thrombosis ◽  
Research Funding ◽  
Thrombin Generation ◽  
Factor Xii ◽  
Wild Type ◽  
Factor Xi ◽  
Endogenous Thrombin Potential ◽  
Free Dna ◽  
Normal Plasma ◽  
Rate Of Activation

Abstract Components of the blood coagulation mechanism are activated during infections as part of the innate immune response to invading microorganisms. This process is crucial for limiting spread of infection; however, excessive activation of coagulation can contribute to thrombotic tissue ischemia and systemic inflammation. During a variety of conditions associated with leukocyte activation and tissue damage, including sepsis, levels of cell free DNA rise in plasma. Neutrophils are one source of free DNA, releasing chromatin upon activation to form neutrophil extracellular traps (NETs). DNA in NETs form a physical barrier that contains microorganisms, while histones and antimicrobial proteins associated with DNA have bactericidal properties. NETs trigger platelet activation and coagulation, and likely contribute to inflammation, thrombosis and disseminated intravascular coagulation in sepsis. In a murine venous thrombosis model, neutrophils and NETs appear to contribute to thrombus formation through a process involving factor XII (fXII) (von Bruhl et al. J Exp Med 2012;209:819). When plasma fXII binds to anionic surfaces it is converted to the protease fXIIa. The results with the mouse model suggest that DNA, an anionic polymer, contributes to thrombosis by enhancing fXII activation. FXIIa contributes to thrombin generation and thrombosis by converting zymogen factor XI (fXI), to the protease factor XIa (fXIa). FXI has been implicated in the pathology of sepsis and thrombosis in animal models. Mice lacking fXI have better survival than wild type mice after ligation and puncture of the cecum, and are more resistant to Listeria infection. Inhibition or deficiency of fXI/fXIa confers an antithrombotic phenotype in rodents, rabbits and primates. Furthermore, epidemiologic data support a role for fXI in arterial and venous thrombosis in humans. FXI is activated in plasma by fXIIa or thrombin; however, the reactions proceed slowly in the absence of anionic substances. This suggests that a cofactor with anionic properties is required for fXI activation in vivo. For example, polymers of inorganic phosphate (polyphosphate or polyP) released by platelets enhance fXI activation by thrombin 3000-fold and by fXIIa 30-fold. PolyP also induces fXI and fXII autoactivation. The backbone of DNA is a type of phosphate polymer. We examined the capacity of DNA to enhance fXI and fXII activation and to contribute to fXI/fXII-dependent plasma coagulation. We isolated DNA from human peripheral blood leukocytes. Like polyP, DNA induced fXII autoactivation. Similarly, fXI underwent autoactivated in the presence of DNA, with the rate of activation increasing as DNA concentration increased. For reactions with either fXII or fXI, the enhancing effect of DNA was neutralized by treatment with DNAse. DNA, but not DNAse treated DNA, enhanced fXI activation by fXIIa 4-fold and by thrombin 30-fold compared to reactions without DNA. FXI is a dimeric protein composed of two identical subunits. PolyP binds to each fXI subunit through two anion binding sites (ABS), one on the fXI apple 3 domain (ABS1) and the other on the fXI catalytic domain (ABS2). These interactions are required for polyP-mediated enhancement of fXI activation by thrombin and fXIIa. Using DNA as a cofactor, the rate of activation of fXI lacking ABS1 by thrombin or fXIIa was 4-fold slower than for wild type fXI, while DNA failed to enhance activation of fXI lacking ABS2. This indicates that binding of fXI to DNA through the ABSs is required for expression of the DNA cofactor effect. Addition of DNA (50 ug/ml) induced thrombin generation in normal plasma (Endogenous Thrombin Potential 356 nM.min) through a process that was blocked by a fXIIa inhibitor (corn trypsin inhibitor) or a monoclonal antibody to fXI. Thrombin generation is dependent on fXI in normal plasma triggered to clot with a low (0.2 pM) concentration of tissue factor. Addition of DNA (50 ug/ml) to this system increased peak thrombin generation and endogenous thrombin potential by ~50%, while shortening time to peak thrombin potential. This effect was completely neutralized by an antibody to fXI. In conclusion, fXII and fXI have a propensity to bind to, and become activated on, anionic polymers and surfaces. Our results suggest that DNA released from leukocytes or damaged tissues could enhance activation of these protease zymogens, facilitating their contribution to hypercoagulability and inflammation. Disclosures Gailani: Aronora: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Dyax: Consultancy, Research Funding; Instrument Laboratory: Consultancy, Research Funding; Isis: Consultancy; Merck: Consultancy; Novartis: Consultancy.

Proximal deep venous thrombosis following PTA of the superficial femoral artery – an obligation to disclose a complication that is rarely taken into account

VASA ◽  
2006 ◽  
Vol 35 (1) ◽  
pp. 41-44 ◽  
Author(s):  
Klein-Weigel ◽  
Pillokat ◽  
Klemens ◽  
Köning ◽  
Wolbergs ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Deep Venous Thrombosis ◽  
Femoral Artery ◽  
Superficial Femoral Artery ◽  
Rare Complication ◽  
Femoral Vein ◽  
Vein Thrombosis ◽  
Explicit Information ◽  
Life Threatening ◽  
Legal Consequences

We report two cases of femoral vein thrombosis after arterial PTA and subsequent pressure stasis. We discuss the legal consequences of these complications for information policies. Because venous thrombembolism following an arterial PTA might cause serious sequel or life threatening complications, there is a clear obligation for explicit information of the patients about this rare complication.

New agents for thromboprotection

2015 ◽  
Vol 35 (04) ◽  
pp. 338-350 ◽  
Author(s):  
L. Labberton ◽  
E. Kenne ◽  
T. Renné
Keyword(s):  
Current Knowledge ◽  
Thrombus Formation ◽  
Coagulation Cascade ◽  
Factor Xii ◽  
Bleeding Tendency ◽  
New Agents ◽  
Mechanistic Basis ◽  
Normal Hemostasis ◽  
Coagulation Pathway

SummaryBlood coagulation is essential for hemostasis, however excessive coagulation can lead to thrombosis. Factor XII starts the intrinsic coagulation pathway and contact-induced factor XII activation provides the mechanistic basis for the diagnostic aPTT clotting assay. Despite its function for fibrin formation in test tubes, patients and animals lacking factor XII have a completely normal hemostasis. The lack of a bleeding tendency observed in factor XII deficiency states is in sharp contrast to deficiencies of other components of the coagulation cascade and factor XII has been considered to have no function for coagulation in vivo. Recently, experimental animal models showed that factor XII is activated by an inorganic polymer, polyphosphate, which is released from procoagulant platelets and that polyphosphate-driven factor XII activation has an essential role in pathologic thrombus formation. Cumulatively, the data suggest to target polyphosphate, factor XII, or its activated form factor XIIa for anticoagulation. As the factor XII pathway specifically contributes to thrombosis but not to hemostasis, interference with this pathway provides a unique opportunity for safe anticoagulation that is not associated with excess bleeding.The review summarizes current knowledge on factor XII functions, activators and inhibitors.

scholarly journals Can quantifying morphology and TMEM119 expression distinguish between microglia and infiltrating macrophages after ischemic stroke and reperfusion in male and female mice?

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Kimberly F. Young ◽  
Rebeca Gardner ◽  
Victoria Sariana ◽  
Susan A. Whitman ◽  
Mitchell J. Bartlett ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Brain Injury ◽  
Western Blot ◽  
Calcium Binding ◽  
Transmembrane Protein ◽  
Brain Regions ◽  
Morphological Data ◽  
Cell Populations ◽  
Male And Female ◽  
Female Mice

AbstractBackgroundIschemic stroke is an acquired brain injury with gender-dependent outcomes. A persistent obstacle in understanding the sex-specific neuroinflammatory contributions to ischemic brain injury is distinguishing between resident microglia and infiltrating macrophages—both phagocytes—and determining cell population-specific contributions to injury evolution and recovery processes. Our purpose was to identify microglial and macrophage populations regulated by ischemic stroke using morphology analysis and the presence of microglia transmembrane protein 119 (TMEM119). Second, we examined sex and menopause differences in microglia/macrophage cell populations after an ischemic stroke.MethodsMale and female, premenopausal and postmenopausal, mice underwent either 60 min of middle cerebral artery occlusion and 24 h of reperfusion or sham surgery. The accelerated ovarian failure model was used to model postmenopause. Brain tissue was collected to quantify the infarct area and for immunohistochemistry and western blot methods. Ionized calcium-binding adapter molecule, TMEM119, and confocal microscopy were used to analyze the microglia morphology and TMEM119 area in the ipsilateral brain regions. Western blot was used to quantify protein quantity.ResultsPost-stroke injury is increased in male and postmenopause female mice vs. premenopause female mice (p< 0.05) with differences primarily occurring in the caudal sections. After stroke, the microglia underwent a region, but not sex group, dependent transformation into less ramified cells (p< 0.0001). However, the number of phagocytic microglia was increased in distal ipsilateral regions of postmenopausal mice vs. the other sex groups (p< 0.05). The number of TMEM119-positive cells was decreased in proximity to the infarct (p< 0.0001) but without a sex group effect. Two key findings prevented distinguishing microglia from systemic macrophages. First, morphological data were not congruent with TMEM119 immunofluorescence data. Cells with severely decreased TMEM119 immunofluorescence were ramified, a distinguishing microglia characteristic. Second, whereas the TMEM119 immunofluorescence area decreased in proximity to the infarcted area, the TMEM119 protein quantity was unchanged in the ipsilateral hemisphere regions using western blot methods.ConclusionsOur findings suggest that TMEM119 is not a stable microglia marker in male and female mice in the context of ischemic stroke. Until TMEM119 function in the brain is elucidated, its use to distinguish between cell populations following brain injury with cell infiltration is cautioned.

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