Project description:Background Ischemic stroke becomes a major cause of death and disability. It can develop due to intravascular or cardiac thromboemboli. Animal models that reflect diverse stroke mechanisms remain under development. Using photochemical thrombosis, we developed a feasible zebrafish model according to the thrombus location (intracerebral vs. intracardiac). We validated the model using real-time imaging and thrombolytic agent. Methods We used transgenic zebrafish larvae (flk:gfp), which express specific fluorescence in endothelial cells. We injected Rose Bengal, a photosensitizer as a mixture of photosensitizer, and a fluorescent agent into the cardinal vein of the larvae. We then evaluated real-time thrombosis in vivo by inducing thrombosis through exposure to a confocal laser (560 nm) and staining the blood flow (RITC-dextran). We validated intracerebral and intracardiac thrombotic models with checking the activity of tissue plasminogen activator (tPA). Results The photochemical agent induced the formation of intracerebral thrombi in transgenic zebrafish. Real-time imaging techniques confirmed the formation of the thrombi. The damage and apoptosis of the vessel's endothelial cells were seen in the in vivo model. An intracardiac thrombosis model was developed by the same method using photothrombosis, and the model was validated through thrombolysis by tPA. Conclusions We developed and validated two zebrafish thrombosis models that are readily available, cost-effective, and intuitive for assessing the efficacy of thrombolytic agents. These models can be used for a broad spectrum of future studies, such as screening and efficacy assessment of new antithrombotic agents.
Project description:BackgroundA wide variety of laboratory hemostasis tests is available, but the majority is plasma-based, static and unable to assess platelet function and fibrin formation simultaneously. The Total Thrombus-Formation Analysis System (T-TAS) is a microchip-based flow chamber system that simulates in vivo conditions for evaluating whole blood thrombogenicity.AimA comprehensive overview of its applicability in different thrombosis and hemostasis related clinical situations is lacking and therefore this scoping review was performed.Materials & methodsA literature search was done using the electronic databases PubMed, Scopus and Embase on January 7, 2024. Original studies assessing the usefulness of the T-TAS in thrombosis and hemostasis related clinical situations were eligible for this scoping review.ResultsA total of 28 studies were included; six studies investigating the role of the T-TAS in congenital bleeding disorders, five studies using the T-TAS to assess 1-year bleeding risk in patients on antiplatelet or anticoagulant medications, four studies investigating the effects of thrombocytopenia and hemodialysis on thrombus formation as measured by the T-TAS, 11 studies testing the applicability of the T-TAS in the monitoring of anticoagulant and antiplatelet therapies and eventually two studies on the ability of the T-TAS to assess the thrombogenicity in different disease entities.Discussion & conclusionThe T-TAS method is an interesting technology that mimics the complex biological coagulation process using shear forces, creating a "blood vessel component on a chip". More research is needed, but it could eventually function as a screening test for platelet function and coagulation. Moreover, it could be used to detect the presence of anticoagulant and/or antiplatelet medication.
Project description:The plasma zymogens factor XII (fXII) and factor XI (fXI) contribute to thrombosis in a variety of mouse models. These proteins serve a limited role in hemostasis, suggesting that antithrombotic therapies targeting them may be associated with low bleeding risks. Although there is substantial epidemiologic evidence supporting a role for fXI in human thrombosis, the situation is not as clear for fXII. We generated monoclonal antibodies (9A2 and 15H8) against the human fXII heavy chain that interfere with fXII conversion to the protease factor XIIa (fXIIa). The anti-fXII antibodies were tested in models in which anti-fXI antibodies are known to have antithrombotic effects. Both anti-fXII antibodies reduced fibrin formation in human blood perfused through collagen-coated tubes. fXII-deficient mice are resistant to ferric chloride-induced arterial thrombosis, and this resistance can be reversed by infusion of human fXII. 9A2 partially blocks, and 15H8 completely blocks, the prothrombotic effect of fXII in this model. 15H8 prolonged the activated partial thromboplastin time of baboon and human plasmas. 15H8 reduced fibrin formation in collagen-coated vascular grafts inserted into arteriovenous shunts in baboons, and reduced fibrin and platelet accumulation downstream of the graft. These findings support a role for fXII in thrombus formation in primates.
Project description:Venous thromboembolism (VTE), the third leading cardiovascular complication, requires more understanding at molecular levels. Here, we have identified miR-145 as a key molecule for regulating thrombus formation in venous thrombosis (VT) employing network based bioinformatics approach and in vivo experiments. Levels of miR-145 showed an inverse correlation with thrombus load determined by coagulation variables. MiRNA target prediction tools and in vitro study identified tissue factor (TF) as a target gene for miR-145. The restoration of miR-145 levels in thrombotic animals via in vivo miR-145 mimic delivery resulted in decreased TF level and activity, accompanied by reduced thrombogenesis. MiR-145 levels were also reduced in VT patients and correlated with increased TF levels in patients, thereby, confirming our preclinical findings. Our study identifies a previously undescribed role of miRNA in VT by regulating TF expression. Therefore, restoration of miR-145 levels may serve as a promising therapeutic strategy for management of VT.
Project description:Acute thromboembolic events have been frequently reported in patients with coronavirus disease 2019 (COVID-19) due to an increase in the coagulation system activity and endothelial dysfunction. This report describes a patient with COVID-19 who initially reported respiratory symptoms and developed acute lower limb ischemia secondary to extensive macrovascular arterial thrombosis, which was treated with thrombectomy. The development of such extensive arterial thrombosis with anticoagulants at therapeutic doses is a new sign of increased viral pathogenicity, and it is necessary to develop and apply updated prophylaxis protocols for thrombosis in these patients.
Project description:Background and objectivesAnti-heat shock protein (HSP)60 autoantibodies are associated with atherosclerosis and are known to affect endothelial cells in vitro. However, their role in thrombus formation remains unclear. We hypothesized that anti-HSP60 autoantibodies could potentiate thrombosis, and evaluated the effect of anti-murine HSP60 antibodies in a ferric chloride (FeCl3)-induced murine model of carotid artery injury.MethodsAnti-HSP60, or control, IgG was administered to BALB/c mice 48 h prior to inducing carotid artery injury, and blood flow was monitored using an ultrasound probe.ResultsThrombus formation was more rapid and stable in anti-HSP60 IGG-treated mice than in controls (blood flow=1.7%+/-0.6% vs. 34%+/-12.6%, P=0.0157). Occlusion was complete in all anti-HSP60 IgG-treated mice (13/13), with no reperfusion being observed. In contrast, 64% (9/14) of control mice had complete occlusion, with reperfusion occurring in 6/9 mice. Thrombi were significantly larger in anti-HSP60 IgG-treated mice (P=0.0001), and contained four-fold more inflammatory cells (P=0.0281) than in controls. Non-injured contralateral arteries of anti-HSP60 IgG-treated mice were also affected, exhibiting abnormal endothelial cell morphology and significantly greater von Willebrand factor (VWF) and P-selectin expression than control mice (P=0.0024 and P=0.001, respectively).ConclusionsIn summary, the presence of circulating anti-HSP60 autoantibodies resulted in increased P-selectin and VWF expression and altered cell morphology in endothelial cells lining uninjured carotid arteries, and promoted thrombosis and inflammatory cell recruitment in FeCl3-injured carotid arteries. These findings suggest that anti-HSP60 autoantibodies may constitute an important prothrombotic risk factor in cardiovascular disease in human vascular disease.
Project description:Genetically modified mice are indispensable for establishing the roles of platelets in arterial thrombosis and hemostasis. Microfluidics assays using anticoagulated whole blood are commonly used as integrative proxy tests for platelet function in mice. In the present study, we quantified the changes in collagen-dependent thrombus formation for 38 different strains of (genetically) modified mice, all measured with the same microfluidics chamber. The mice included were deficient in platelet receptors, protein kinases or phosphatases, small GTPases or other signaling or scaffold proteins. By standardized re-analysis of high-resolution microscopic images, detailed information was obtained on altered platelet adhesion, aggregation and/or activation. For a subset of 11 mouse strains, these platelet functions were further evaluated in rhodocytin- and laminin-dependent thrombus formation, thus allowing a comparison of glycoprotein VI (GPVI), C-type lectin-like receptor 2 (CLEC2) and integrin α6β1 pathways. High homogeneity was found between wild-type mice datasets concerning adhesion and aggregation parameters. Quantitative comparison for the 38 modified mouse strains resulted in a matrix visualizing the impact of the respective (genetic) deficiency on thrombus formation with detailed insight into the type and extent of altered thrombus signatures. Network analysis revealed strong clusters of genes involved in GPVI signaling and Ca2+ homeostasis. The majority of mice demonstrating an antithrombotic phenotype in vivo displayed with a larger or smaller reduction in multi-parameter analysis of collagen-dependent thrombus formation in vitro. Remarkably, in only approximately half of the mouse strains that displayed reduced arterial thrombosis in vivo, this was accompanied by impaired hemostasis. This was also reflected by comparing in vitro thrombus formation (by microfluidics) with alterations in in vivo bleeding time. In conclusion, the presently developed multi-parameter analysis of thrombus formation using microfluidics can be used to: (i) determine the severity of platelet abnormalities; (ii) distinguish between altered platelet adhesion, aggregation and activation; and (iii) elucidate both collagen and non-collagen dependent alterations of thrombus formation. This approach may thereby aid in the better understanding and better assessment of genetic variation that affect in vivo arterial thrombosis and hemostasis.
Project description:BackgroundWe have used the advantages of the zebrafish model system to demonstrate which of the vertebrate myosin light chain kinase (MLCK) genes is expressed in thrombocytes and important for thrombus formation.Methods and resultsHere we report that Mlck1a is an essential component of thrombus formation. Phylogenetic data revealed four zebrafish orthologous for three human MLCK genes. To investigate expression of the zebrafish mlck genes in thrombocytes we compared GFP-tagged platelets with other cells by microarray analysis, and showed that mlck1a expression was 4.5-fold enriched in platelets. Furthermore, mlck1a mRNA and mRNA for the platelet-specific cd41 co-localized in thrombi. Expression of other mlck subtypes was lower in GFP-tagged platelets (mlck1b; 0.77-fold enriched) and absent in thrombi (mlck1b, -2, -3). To investigate the role of Mlck1a in thrombus formation, we knocked down mlck1a using two morpholinos. This resulted in impaired morphology changes of platelets adhering on fibrinogen. In a thrombosis model, in which thrombocytes adhere to the vessel wall damaged by laser irradiation, thrombus formation was slowed down in mlck1a-deficient embryos.ConclusionWe conclude that Mlck1a is the subtype of MLCK that contributes to platelet shape change and thrombus formation.
Project description:AimsJNJ-64179375 (hereafter JNJ-9375) is a first-in-class, highly specific, large molecule, exosite 1 thrombin inhibitor. In preclinical studies, JNJ-9375 demonstrated robust antithrombotic protection with a wider therapeutic index when compared to apixaban. The purpose of the present study was to examine for the first time the antiplatelet, anticoagulant and antithrombotic effects of JNJ-9375 in a translational model of ex vivo human thrombosis.Methods and resultsFifteen healthy volunteers participated in a double-blind randomized crossover study of JNJ-9375 (2.5, 25, and 250 μg/mL), bivalirudin (6 μg/mL; positive control), and matched placebo. Coagulation, platelet activation, and thrombus formation were determined using coagulation assays, flow cytometry, and an ex vivo perfusion chamber, respectively.JNJ-9375 caused concentration-dependent prolongation of all measures of blood coagulation (prothrombin time, activated partial thromboplastin time, and thrombin time; P < 0.001 for all) and agonist selective inhibition of thrombin (0.1 U/mL) stimulated platelet p-selectin expression (P < 0.001) and platelet-monocyte aggregates (P = 0.002). Compared to placebo, JNJ-9375 (250 μg/mL) reduced mean total thrombus area by 41.1% (95% confidence intervals 22.3 to 55.3%; P < 0.001) at low shear and 32.3% (4.9 to 51.8%; P = 0.025) at high shear. Under both shear conditions, there was a dose-dependent decrease in fibrin-rich thrombus (P < 0.001 for both) but not platelet-rich thrombus (P = ns for both).ConclusionExosite 1 inhibition with JNJ-9375 caused prolongation of blood coagulation, selective inhibition of thrombin-mediated platelet activation, and reductions in ex vivo thrombosis driven by a decrease in fibrin-rich thrombus formation. JNJ-9375 represents a novel class of anticoagulant with potential therapeutic applications.
Project description:BackgroundThe cremaster arteriole laser-induced injury model is a powerful technique with which to investigate the molecular mechanisms that drive thrombus formation. This model is capable of direct visualization and quantification of accumulation of thrombus constituents, including both platelets and fibrin. However, a large degree of variability in platelet accumulation and fibrin formation is observed between thrombi. Strategies to understand this variability will enhance performance and standardization of the model. We determined whether ablation injury size contributes to variation in platelet accumulation and fibrin formation and, if so, whether incorporating ablation injury size into measurements reduces variation.MethodsThrombus formation was initiated by laser-induced injury of cremaster arterioles of mice (n=59 injuries). Ablation injuries within the vessel wall were consistently identified and quantified by measuring the length of vessel wall injury observed immediately following laser-induced disruption. Platelet accumulation and fibrin formation as detected by fluorescently-labeled antibodies were captured by digital intra-vital microscopy.ResultsLaser-induced disruption of the vessel wall resulted in ablation injuries of variable length (18-95 μm) enabling interrogation of the relationship between injury severity and thrombus dynamics. Strong positive correlations were observed between vessel injury length and both platelet and fibrin when the data are transformed as area under the curve (Spearman r = 0.80 and 0.76 respectively). Normalization of area under the curve measurements by injury length reduced intraclass coefficients of variation among thrombi and improved hypothesis testing when comparing different data sets.ConclusionsMeasurement of vessel wall injury length provides a reliable and robust marker of injury severity. Injury length can effectively normalize measurements of platelet accumulation and fibrin formation improving data interpretation and standardization.