JAK2V617F mutation is associated with an increased risk for athero-thrombotic cardiovascular disease, but its role in aortic disease development and complications remains unknown. In a cohort of ...patients with myeloproliferative neoplasm, JAK2V617F mutation was identified as an independent risk factor for dilation of both the ascending and descending thoracic aorta. Using single-cell RNA-seq, complementary genetically-modified mouse models, as well as pharmacological approaches, we found that JAK2V617F mutation was associated with a pathogenic pro-inflammatory phenotype of perivascular tissue-resident macrophages, which promoted deleterious aortic wall remodeling at early stages, and dissecting aneurysm through the recruitment of circulating monocytes at later stages. Finally, genetic manipulation of tissue-resident macrophages, or treatment with a Jak2 inhibitor, ruxolitinib, mitigated aortic wall inflammation and reduced aortic dilation and rupture. Overall, JAK2V617F mutation drives vascular resident macrophages toward a pathogenic phenotype and promotes dissecting aortic aneurysm.
Neutrophils participate in the pathogenesis of thrombosis through the formation of neutrophil extracellular traps (NETs). Thrombosis is the main cause of morbidity and mortality in patients with ...myeloproliferative neoplasms (MPNs). Recent studies have shown an increase in NET formation (NETosis) both in patients with JAK2V617F neutrophils and in mouse models, and reported the participation of NETosis in the pathophysiology of thrombosis in mice.
This study investigated whether JAK2V617F neutrophils are sufficient to promote thrombosis or whether their cooperation with other blood cell types is necessary.
NETosis was studied in PF4iCre;Jak2
mice expressing JAK2V617F in all hematopoietic lineages, as occurs in MPNs, and in MRP8Cre;Jak2
mice in which JAK2V617F is expressed only in leukocytes.
In PF4iCre;Jak2
mice, an increase in NETosis and spontaneous lung thrombosis abrogated by DNAse administration were observed. The absence of spontaneous NETosis or lung thrombosis in MRP8Cre;Jak2
mice suggested that mutated neutrophils alone are not sufficient to induce thrombosis. Ex vivo experiments demonstrated that JAK2V617F-mutated platelets trigger NETosis by JAK2V617F-mutated neutrophils. Aspirin treatment in PF4iCre;Jak2
mice reduced NETosis and reduced lung thrombosis. In cytoreductive-therapy-free patients with MPN treated with aspirin, plasma NET marker concentrations were lower than that in patients with MPN not treated with aspirin.
Our study demonstrates that JAK2V617F neutrophils alone are not sufficient to promote thrombosis; rather, platelets cooperate with neutrophils to promote NETosis in vivo. A new role for aspirin in thrombosis prevention in MPNs was also identified.
The discovery of the JAK2V617F mutation has made the diagnosis of polycythemia vera (PV) much easier, but the pathogenesis of PV is still incompletely understood. In particular, it is not yet ...elucidated how a single mutation can be found in multiple myeloproliferative disorders (MPD) and myelodysplastic syndromes with ring sideroblasts and whether the sole JAK2V617F is sufficient to induce a MPD in humans. Several hypotheses are under investigation such as differences in the targeted hematopoietic stem cells (HSC), host modifier polymorphisms, intensity of JAK2V617F signaling, presence of other somatic mutations, or the presence of a pre-JAK2 event that may vary according to the MPD phenotype. Multiple studies have provided some evidence for and against each hypothesis, but it now seems possible to reconcile these hypotheses into a model that will need to be tested using newly developed tools. Recent investigations have also led to new treatment modalities that could benefit patients with PV.
The lack of innovation in Von Willebrand disease (VWD) originates from many factors including the complexity and heterogeneity of the disease but also from a lack of recognition of the impact of the ...bleeding symptoms experienced by VWD patients. Recently, a few research initiatives aiming to move past replacement therapies using plasma-derived or recombinant Von Willebrand factor (VWF) concentrates have started to emerge. Here we report an original approach using synthetic platelet (SP) nanoparticles for treatment of VWD type 2B (VWD-2B) and severe VWD (type 3 VWD). SP are liposomal nanoparticles decorated with peptides enabling them to concomitantly bind to collagen, VWF and activated platelets. In vitro, using various microfluidic assays, we show the efficacy of SP to improve thrombus formation in VWF-deficient condition (with human platelets) or using blood from VWD-2B mice and VWF-deficient mice (VWF-KO, i.e., type 3 VWD). In vivo, using a tail clip assay, SP treatment reduced blood loss by 35% in VWD-2B mice and 68% in VWF-KO mice. Additional studies using nanoparticles decorated with various combinations of peptides demonstrated that the collagen binding peptide, although not sufficient by itself, was absolutely crucial for SP efficacy in VWD-2B while all three peptides appeared necessary for VWF-KO mice. Clot imaging by immunofluorescence and scanning electron microscopy revealed that SP treatment of VWF-KO mice led to a strong clot, similar to those obtained in wild-type mice. Altogether, our results show that SP could represent an attractive therapeutic alternative for VWD, especially considering their long half-life and stability.
Bilateral adrenal hemorrhage is a rare cause of adrenal insufficiency which has been rarely associated with myeloproliferative neoplasms. Here, we report two cases of bilateral adrenal hemorrhage ...revealed by abdominal pain, malaise, and fatigue in two octogenarian males previously diagnosed with JAK2 V617F-positive essential thrombocythemia. Both patients were on long-term direct oral anticoagulant treatment for atrial fibrillation. Evolution was favorable under steroid replacement therapy, associated with cytoreduction, aspirin, and switch of direct oral anticoagulants for vitamin K antagonists.
Summary
Immune thrombocytopenia (ITP) is defined by a low platelet count that can trigger potentially life‐threatening haemorrhages. Three‐quarters of adult patients exhibit persistent or chronic ...disease and require second‐line treatments. Among these, rituximab, an anti‐CD20 antibody, has yielded valuable results, with global responses in 60% of patients at 6 months and complete responses in 30% at 5 years. Factors predictive of response to ITP therapy would help physicians choose optimal treatments. We retrospectively analysed clinical courses, biological markers and blood lymphocyte subset numbers of 72 patients on rituximab to treat persistent/chronic ITP followed‐up in our department between 2007 and 2021, divided into three groups according to the platelet count at 6 months: complete, partial or no response. Among all studied parameters, a low number of CD3−CD16+CD56+ circulating NK cells was associated with the complete response to rituximab. We also found that, after rituximab therapy, complete responders exhibited increased NK and decreased activated CD8+ T cell percentages. These results emphasize that the role played by NK cells in ITP remains incompletely known but that factors predictive of response to rituximab can be easily derived using blood lymphocyte subset data.
Graphical showing the modifications of the lymphocyte subsets from blood of 72 ITP patients compared to controls (left) and according to the response to rituximab (right).
Myeloproliferative disorders are clonal haematopoietic stem cell malignancies characterized by independency or hypersensitivity of haematopoietic progenitors to numerous cytokines. The molecular ...basis of most myeloproliferative disorders is unknown. On the basis of the model of chronic myeloid leukaemia, it is expected that a constitutive tyrosine kinase activity could be at the origin of these diseases. Polycythaemia vera is an acquired myeloproliferative disorder, characterized by the presence of polycythaemia diversely associated with thrombocytosis, leukocytosis and splenomegaly. Polycythaemia vera progenitors are hypersensitive to erythropoietin and other cytokines. Here, we describe a clonal and recurrent mutation in the JH2 pseudo-kinase domain of the Janus kinase 2 (JAK2) gene in most (> 80%) polycythaemia vera patients. The mutation, a valine-to-phenylalanine substitution at amino acid position 617, leads to constitutive tyrosine phosphorylation activity that promotes cytokine hypersensitivity and induces erythrocytosis in a mouse model. As this mutation is also found in other myeloproliferative disorders, this unique mutation will permit a new molecular classification of these disorders and novel therapeutical approaches.
Coronavirus disease 2019 (COVID-19) can cause life-threatening acute respiratory distress syndrome (ARDS). Recent data suggest a role for neutrophil extracellular traps (NETs) in COVID-19-related ...lung damage partly due to microthrombus formation. Besides, pulmonary embolism (PE) is frequent in severe COVID-19 patients, suggesting that immunothrombosis could also be responsible for increased PE occurrence in these patients. Here, we evaluate whether plasma levels of NET markers measured shorty after admission of hospitalized COVID-19 patients are associated with clinical outcomes in terms of clinical worsening, survival, and PE occurrence.
Ninety-six hospitalized COVID-19 patients were included, 50 with ARDS (severe disease) and 46 with moderate disease. We collected plasma early after admission and measured 3 NET markers: total DNA, myeloperoxidase (MPO)-DNA complexes, and citrullinated histone H3. Comparisons between survivors and non-survivors and patients developing PE and those not developing PE were assessed by Mann-Whitney test.
Analysis in the whole population of hospitalized COVID-19 patients revealed increased circulating biomarkers of NETs in patients who will die from COVID-19 and in patients who will subsequently develop PE. Restriction of our analysis in the most severe patients, i.e., the ones who enter the hospital for COVID-19-related ARDS, confirmed the link between NET biomarker levels and survival but not PE occurrence.
Our results strongly reinforce the hypothesis that NETosis is an attractive therapeutic target to prevent COVID-19 progression but that it does not seem to be linked to PE occurrence in patients hospitalized with COVID-19.
Abstract
Aims
Hedgehog (Hh) signalling has been shown to be re-activated in ischaemic tissues and participate in ischaemia-induced angiogenesis. Sonic Hedgehog (Shh) is upregulated by more than ...80-fold in the ischaemic skeletal muscle, however its specific role in ischaemia-induced angiogenesis has not yet been fully investigated.
The purpose of the present study was to investigate the role of endogenous Shh in ischaemia-induced angiogenesis.
Methods and results
To this aim, we used inducible Shh knock-out (KO) mice and unexpectedly found that capillary density was significantly increased in re-generating muscle of Shh deficient mice 5 days after hind limb ischaemia was induced, demonstrating that endogenous Shh does not promote angiogenesis but more likely limits it. Myosin and MyoD expression were equivalent in Shh deficient mice and control mice, indicating that endogenous Shh is not required for ischaemia-induced myogenesis. Additionally, we observed a significant increase in macrophage infiltration in the ischaemic muscle of Shh deficient mice. Our data indicate that this was due to an increase in chemokine expression by myoblasts in the setting of impaired Hh signalling, using tissue specific Smoothened conditional KO mice. The increased macrophage infiltration in mice deficient for Hh signalling in myocytes was associated with increased VEGFA expression and a transiently increased angiogenesis, demonstrating that Shh limits inflammation and angiogenesis indirectly by signalling to myocytes.
Conclusion
Although ectopic administration of Shh has previously been shown to promote ischaemia-induced angiogenesis, the present study reveals that endogenous Shh does not promote ischaemia-induced angiogenesis. On the contrary, the absence of Shh leads to aberrant ischaemic tissue inflammation and a transiently increased angiogenesis.
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