The principal morbidity and mortality in patients with essential thrombocythemia (ET) and polycythemia rubra vera (PV) stems from thrombotic events. Most patients with ET/PV harbor a JAK2V617F ...mutation, but its role in the thrombotic diathesis remains obscure. Platelet function studies in patients are difficult to interpret because of interindividual heterogeneity, reflecting variations in the proportion of platelets derived from the malignant clone, differences in the presence of additional mutations, and the effects of medical treatments. To circumvent these issues, we have studied a JAK2V617F knock-in mouse model of ET in which all megakaryocytes and platelets express JAK2V617F at a physiological level, equivalent to that present in human ET patients. We show that, in addition to increased differentiation, JAK2V617F-positive megakaryocytes display greater migratory ability and proplatelet formation. We demonstrate in a range of assays that platelet reactivity to agonists is enhanced, with a concomitant increase in platelet aggregation in vitro and a reduced duration of bleeding in vivo. These data suggest that JAK2V617F leads to intrinsic changes in both megakaryocyte and platelet biology beyond an increase in cell number. In support of this hypothesis, we identify multiple differentially expressed genes in JAK2V617F megakaryocytes that may underlie the observed biological differences.
•JAK2V617F causes intrinsic changes in the process of platelet formation from megakaryocytes.•JAK2V617F platelets are prothrombotic and demonstrate increased reactivity to different agonists.
Preventive zinc supplementation provided as a stand-alone dispersible tablet, or via home fortification as multiple micronutrient powders (MNPs), has been considered a potential strategy to prevent ...zinc deficiency and improve health (including immune) outcomes among children in low- and middle-income countries. However, the impact of zinc supplementation on immune profiles has not been well characterized. We sought to define the effect of zinc supplementation on peripheral blood gene expression and cytokine levels among young children in Dhaka, Bangladesh. In a sub-study of a large randomized, controlled, community-based efficacy trial where children 9–11 months of age received one of the following interventions on a daily basis for 24 weeks: (1) MNPs containing 10 mg of zinc; (2) dispersible tablet containing 10 mg zinc; or (3) placebo powder, we used RNA sequencing to profile the peripheral blood gene expression, as well as highly sensitive multiplex assays to detect cytokine profiles. We profiled samples from 100 children enrolled in the parent trial (zinc MNPs 28, zinc tablets 39, placebo 33). We did not detect an effect from either zinc intervention on differential peripheral blood gene expression at the end of the intervention, or an effect from the intervention on changes in gene expression from baseline. We also did not detect an effect from either intervention on cytokine concentrations. Exploratory analysis did not identify an association between undernutrition (defined as stunting, underweight or wasting) and peripheral blood gene expression. Zinc interventions in children did not produce a gene expression or cytokine signature in the peripheral blood. However, this study demonstrates a proof of principle that sensitive multi-omic techniques can be applied to samples collected in field studies.
Wnt signaling is involved in numerous aspects of vertebrate development and homeostasis, including the formation and function of blood cells. Here, we show that canonical and noncanonical Wnt ...signaling pathways are present and functional in megakaryocytes (MKs), with several Wnt effectors displaying MK-restricted expression. Using the CHRF288-11 cell line as a model for human MKs, the canonical Wnt3a signal was found to induce a time and dose-dependent increase in β-catenin expression. β-catenin accumulation was inhibited by the canonical antagonist dickkopf-1 (DKK1) and by the noncanonical agonist Wnt5a. Whole genome expression analysis demonstrated that Wnt3a and Wnt5a regulated distinct patterns of gene expression in MKs, and revealed a further interplay between canonical and noncanonical Wnt pathways. Fetal liver cells derived from low-density-lipoprotein receptor-related protein 6-deficient mice (LRP6−/−), generated dramatically reduced numbers of MKs in culture of lower ploidy (2N and 4N) than wild-type controls, implicating LRP6-dependent Wnt signaling in MK proliferation and maturation. Finally, in wild-type mature murine fetal liver-derived MKs, Wnt3a potently induced proplatelet formation, an effect that could be completely abrogated by DKK1. These data identify novel extrinsic regulators of proplatelet formation, and reveal a profound role for Wnt signaling in platelet production.
•Wnt signaling is essential for MK proliferation and maturation in addition to profoundly stimulating proplatelet formation.•These observations suggest that mature megakaryocytes may be able to respond to known Wnt gradients in the osteoblastic and vascular niches.
Somatic mutations in the endoplasmic reticulum chaperone calreticulin (CALR) are detected in approximately 40% of patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF). ...Multiple different mutations have been reported, but all result in a +1-bp frameshift and generate a novel protein C terminus. In this study, we generated a conditional mouse knockin model of the most common CALR mutation, a 52-bp deletion. The mutant novel human C-terminal sequence is integrated into the otherwise intact mouse CALR gene and results in mutant CALR expression under the control of the endogenous mouse locus. CALRdel/+ mice develop a transplantable ET-like disease with marked thrombocytosis, which is associated with increased and morphologically abnormal megakaryocytes and increased numbers of phenotypically defined hematopoietic stem cells (HSCs). Homozygous CALRdel/del mice developed extreme thrombocytosis accompanied by features of MF, including leukocytosis, reduced hematocrit, splenomegaly, and increased bone marrow reticulin. CALRdel/+ HSCs were more proliferative in vitro, but neither CALRdel/+ nor CALRdel/del displayed a competitive transplantation advantage in primary or secondary recipient mice. These results demonstrate the consequences of heterozygous and homozygous CALR mutations and provide a powerful model for dissecting the pathogenesis of CALR-mutant ET and PMF.
•Mutant CALR drives ET and MF in knockin mice.•Mutant CALR expression results in expansion of phenotypic HSCs without a self-renewal advantage.
Increasing evidence suggests that patients with pulmonary arterial hypertension (PAH) demonstrate abnormalities in the bone marrow (BM) and hematopoietic progenitor cells. In addition, PAH is ...associated with myeloproliferative diseases. We have previously demonstrated that low-dose lipopolysaccharide (LPS) is a potent stimulus for the development of PAH in the context of a genetic PAH mouse model of BMPR2 dysfunction. We hypothesized that the hematopoietic progenitor cells might be driving disease in this model. To test this hypothesis, we performed adoptive transfer of BM between wild-type (Ctrl) and heterozygous Bmpr2 null (Mut) mice. Sixteen weeks after BM reconstitution, mice were exposed to low-dose chronic LPS (0.5 mg/kg three times a week for six weeks). Mice underwent right heart catheterization and tissues were removed for histology. After chronic LPS dosing, Ctrl mice in receipt of Mut BM developed PAH, whereas Mut mice receiving Ctrl BM were protected from PAH. BM histology demonstrated an increase in megakaryocytes and there was an increase in circulating platelets in Ctrl mice receiving Mut BM. These findings demonstrate that the hematopoietic stem cell compartment is involved in the susceptibility to PAH in the Mut mouse. The results raise the possibility that hematopoietic stem cell transplantation might be a potential treatment strategy in genetic forms of PAH.
Aim: Hepcidin levels are suppressed during human and murine pregnancy. It is unknown whether hepcidin levels are primarily the result of iron deficiency/utilisation or whether there is a ...pregnancy-specific mechanism for hepcidin suppression. We reasoned that Tmprss6 inhibition would cause constitutive BMP-SMAD signalling and help determine the mechanism of antenatal hepcidin suppression. Method: Female wildtype C57BL/6 mice were treated subcutaneously every 21 days with a GalNAc-siRNA conjugate targeting Tmprss6 (Silence Therapeutics GmbH, Berlin, Germany) or a non-targeting control (NTC) siRNA conjugate. Mice were mated and monitored for pregnancy. Samples were collected from pregnant mice humanely euthanised at E8.5 or E14.5, and unmated controls. Results: Treatment with Tmprss6 siRNA inhibited hepatic Tmprss6 mRNA expression (unmated fold change 0.077, p<0.0001). qPCR Hamp expression was significantly increased in Tmprss6 siRNA-treated mice, compared to NTC-treated mice, at all timepoints. Serum hepcidin, by ELISA, was higher in Tmprss6 siRNA-treated mice than in NTC-treated mice at E14.5 (1126ng/ml vs 178.5, p<0.0001). In unmated mice, serum hepcidin was not significantly elevated (640.9 vs 980.1ng/ml, p=0.224). Across NTC treated pregnancy, Hamp expression and serum hepcidin were reduced at E14.5 compared to unmated ( Hamp fold change E14.5 0.293, p=0.0367; serum hepcidin E14.5 178.5 vs 640.9, p=0.0247). In contrast, Tmprss6 siRNA treatment caused elevated hepcidin through pregnancy (E14.5 1126 vs unmated 980ng/ml, p=0.99); Fig 1a. Maternal liver iron was unchanged between groups. Tmprss6 siRNA reduced placental iron, fetal liver iron, and fetal weight (0.189 vs 0.226g, p<0.0001), Fig 1b. At E8.5/E14.5, Tmprss6 siRNA reduced Mean Cell Volume (E14.5: 41.42 vs 51.72fL, p<0.0001) and Mean Cell Haemoglobin (E14.5: 11.20 vs 15.68pg, p<0.0001); at E14.5 only, maternal anaemia was seen with Tmprss6 siRNA (haemoglobin 9.4 vs 13.85g/L, p=0.0004). Conclusion: Disruption of Tmprss6 increased hepcidin and ablated the hepcidin fall over pregnancy. This may suggest that any pregnancy-related factor which directly suppresses hepcidin cannot overcome Tmprss6 knockdown. Tmprss6 siRNA treatment resulted in iron-restricted erythropoiesis, reduced placental iron and impacted fetal development, despite unchanged liver iron stores.
Iron deficiency, pregnancy, and neonatal development Ataide, Ricardo; Fielding, Katherine; Pasricha, Sant‐Rayn ...
International journal of gynaecology and obstetrics,
August 2023, 2023-Aug, 2023-08-00, 20230801, Letnik:
162, Številka:
S2
Journal Article
Recenzirano
Odprti dostop
Anemia affects 36% of pregnant women worldwide. Of those affected, around 40% is due to iron deficiency (ID). Iron is an essential micronutrient involved in vital processes such as erythropoiesis, ...immune responses, and importantly—during pregnancy—placental and fetal development. Although menstrual bleeding can impact the incidence of ID even before the onset of pregnancy, this narrative review is pregnancy focused and will explore the impact of ID on placental development and iron uptake, fetal development and immunity, and maternal and infant susceptibility to infection. Although there have been advances in this area of research, much is needed to understand the regulation of iron and the effects of ID during pregnancy. Notably, more human studies are essential to generate the best evidence to advance strategies to reduce the incidence of ID during pregnancy to improve maternal, neonatal, and infant health.
Synopsis
Good‐quality studies of human maternal iron deficiency are needed to understand its impact on placental and fetal growth/development and maternal and infant susceptibility to infection.
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