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British Journal of Haematology Oct 2023Immune thrombocytopenia (ITP) is a disorder characterized by low platelets due to increased clearance and decreased platelet production. While ITP has been characterized... (Review)
Review
Immune thrombocytopenia (ITP) is a disorder characterized by low platelets due to increased clearance and decreased platelet production. While ITP has been characterized as an acquired disorder of the adaptive immune system, the resulting platelet autoantibodies provide ancillary links to the innate immune system via antibody interaction with the complement system. Most autoantibodies in patients with ITP are of the IgG1 subclass, which can be potent activators of the classical complement pathway. Antibody-coated platelets can initiate complement activation via the classical pathway leading to both direct platelet destruction and enhanced clearance of C3b-coated platelets by complement receptors. Similar autoantibody interactions with bone marrow megakaryocytes can also result in complement injury and ineffective thrombopoiesis. The development of novel therapeutic complement inhibitors has revived interest in the role of complement in autoantibody-mediated disorders, such as ITP. A recent early-phase clinical trial of a classical complement pathway inhibitor has demonstrated efficacy in a subset of ITP patients refractory to conventional immune modulation. In this review, we will analyse the role of complement in refractory ITP.
Topics: Humans; Purpura, Thrombocytopenic, Idiopathic; Thrombocytopenia; Complement System Proteins; Blood Platelets; Autoantibodies
PubMed: 37735550
DOI: 10.1111/bjh.19070 -
Blood Cells, Molecules & Diseases Jan 2024Thrombopoiesis is the production of platelets from megakaryocytes in the bone marrow of mammals. In fish, thrombopoiesis involves the formation of thrombocytes without...
Thrombopoiesis is the production of platelets from megakaryocytes in the bone marrow of mammals. In fish, thrombopoiesis involves the formation of thrombocytes without megakaryocyte-like precursors but derived from erythrocyte thrombocyte bi-functional precursor cells. One unique feature of thrombocyte differentiation involves the maturation of young thrombocytes in circulation. In this study, we investigated the role of hox genes in zebrafish thrombopoiesis to model platelet production. We selected hoxa10b, hoxb2a, hoxc5a, hoxd3a, and hoxc11b from thrombocyte RNA expression data, and checked whether they are expressed in young or mature thrombocytes. We found hoxa10b, hoxb2a, hoxc5a, and hoxd3a were expressed in both young and mature thrombocytes and hoxc11b was expressed in only young thrombocytes. We then performed knockdowns of these 5 hox genes and found hoxc11b knockdown resulted in thrombocytosis and the rest showed thrombocytopenia. To identify hox genes that could have been missed by the above datasets, we performed knockdowns 47 hox genes in the zebrafish genome and found hoxa9a, and hoxb1a knockdowns resulted in thrombocytopenia and they were expressed in both young and mature thrombocytes. In conclusion, our comprehensive knockdown study identified Hoxa10b, Hoxb2a, Hoxc5a, Hoxd3a, Hoxa9a, and Hoxb1a, as positive regulators and Hoxc11b, as a negative regulator for thrombocyte development.
Topics: Animals; Thrombopoiesis; Zebrafish; Genes, Homeobox; Blood Platelets; Megakaryocytes; Thrombocytopenia; Mammals
PubMed: 37717409
DOI: 10.1016/j.bcmd.2023.102796 -
Arteriosclerosis, Thrombosis, and... Nov 2023Megakaryocytes are commonly known as large, polyploid, bone marrow resident cells that contribute to hemostasis through the production of platelets. Soon after their... (Review)
Review
Megakaryocytes are commonly known as large, polyploid, bone marrow resident cells that contribute to hemostasis through the production of platelets. Soon after their discovery in the 19th century, megakaryocytes were described in tissue locations other than the bone marrow, specifically in the lungs and the blood circulation. However, the localization of megakaryocytes in the lungs and the contribution of lung megakaryocytes to the general platelet pool has only recently been appreciated. Moreover, the conception of megakaryocytes as uniform cells with the sole purpose of platelet production has been challenged. Here, we review the literature on megakaryocyte cell identity and location with a special focus on recent observations of megakaryocyte subpopulations identified by transcriptomic analyses.
Topics: Megakaryocytes; Blood Platelets; Bone Marrow; Bone Marrow Cells; Thrombopoiesis
PubMed: 37675634
DOI: 10.1161/ATVBAHA.123.318782 -
Medical Science Monitor : International... Aug 2023BACKGROUND Thromboembolic episodes, which are largely mediated by blood platelets, are prevalent chronic complications of diabetes. The mean platelet volume (MPV) serves...
BACKGROUND Thromboembolic episodes, which are largely mediated by blood platelets, are prevalent chronic complications of diabetes. The mean platelet volume (MPV) serves as a marker for in vivo platelet activation. This study aimed to assess the factors influencing MPV in 106 patients with type 2 diabetes, compared with 59 non-diabetic individuals at a single center in Poland. MATERIAL AND METHODS We performed linear regression analysis, with MPV as the dependent variable and factors such as age, sex, thrombopoiesis-influencing cytokines, blood pressure, body mass index, glycosylated hemoglobin percentage, platelet count, large platelet count, lipid profile parameters, creatinine concentration, estimated glomerular filtration rate, treatment modalities, and comorbidities as independent variables. MPV was measured using the ADVIA 2120 hematology analyzer, with a reference range of 7-12 fL. RESULTS The analysis revealed that in patients with type 2 diabetes, an increase in platelet count by 10×10³/μL resulted in a decrease in MPV by 0.05 (P<0.001), while an increase in large platelet count by 1×10³/μL led to an increase in MPV by 0.18 (P<0.001). Additionally, patients taking ß-blockers or insulin had lower MPVs by 0.77 (P=0.008) and 5.63 (P<0.001), respectively, compared with those not on these medications. CONCLUSIONS This study delineates the relationship between MPV, platelet parameters, and treatment modalities in type 2 diabetes, paving the way for further research to elucidate underlying mechanisms and potential clinical applications.
Topics: Humans; Diabetes Mellitus, Type 2; Mean Platelet Volume; Poland; Blood Platelets; Insulin
PubMed: 37649249
DOI: 10.12659/MSM.941109 -
Cell Sep 2023Thrombopoietin (THPO or TPO) is an essential cytokine for hematopoietic stem cell (HSC) maintenance and megakaryocyte differentiation. Here, we report the 3.4 Å...
Thrombopoietin (THPO or TPO) is an essential cytokine for hematopoietic stem cell (HSC) maintenance and megakaryocyte differentiation. Here, we report the 3.4 Å resolution cryoelectron microscopy structure of the extracellular TPO-TPO receptor (TpoR or MPL) signaling complex, revealing the basis for homodimeric MPL activation and providing a structural rationalization for genetic loss-of-function thrombocytopenia mutations. The structure guided the engineering of TPO variants (TPO) with a spectrum of signaling activities, from neutral antagonists to partial- and super-agonists. Partial agonist TPO decoupled JAK/STAT from ERK/AKT/CREB activation, driving a bias for megakaryopoiesis and platelet production without causing significant HSC expansion in mice and showing superior maintenance of human HSCs in vitro. These data demonstrate the functional uncoupling of the two primary roles of TPO, highlighting the potential utility of TPO in hematology research and clinical HSC transplantation.
Topics: Animals; Humans; Mice; Cell Cycle; Cryoelectron Microscopy; Receptors, Thrombopoietin; Thrombopoiesis; Thrombopoietin; DNA Methylation
PubMed: 37633268
DOI: 10.1016/j.cell.2023.07.037 -
Journal of Translational Medicine Aug 2023Cyclooxygenase (COX)-2 is a rate-limiting enzyme in the biosynthesis of prostanoids, which is mostly inducible by inflammatory cytokines. The participation of COX-2 in...
BACKGROUND
Cyclooxygenase (COX)-2 is a rate-limiting enzyme in the biosynthesis of prostanoids, which is mostly inducible by inflammatory cytokines. The participation of COX-2 in the maturation of megakaryocytes has been reported but barely studied in primary immune thrombocytopenia (ITP).
METHODS
The expressions of COX-2 and Caspase-1, Caspase-3 and Caspase-3 p17 subunit in platelets from ITP patients and healthy controls (HC), and the expressions of COX-2 and CD41 in bone marrow (BM) of ITP patients were measured and analyzed for correlations. The effects of COX-2 inhibitor on megakaryopoiesis and thrombopoiesis were assessed by in vitro culture of Meg01 cells and murine BM-derived megakaryocytes and in vivo experiments of passive ITP mice.
RESULTS
The expression of COX-2 was decreased and Caspase-1 and Caspase-3 p17 were increased in platelets from ITP patients compared to HC. In platelets from ITP patients, the COX-2 expression was positively correlated with platelet count and negatively correlated to the expression of Caspase-1. In ITP patients BM, the expression of CD41 was positively correlated with the expression of COX-2. COX-2 inhibitor inhibited the count of megakaryocytes and impaired the maturation and platelet production in Meg01 cells and bone marrow-derived megakaryocytes. COX-2 inhibitor aggravated thrombocytopenia and damaged megakaryopoiesis in ITP murine model.
CONCLUSION
COX-2 plays a vital role in the physiologic and pathologic conditions of ITP by intervening the survival of platelets and impairing the megakaryopoiesis and thrombopoiesis of megakaryocytes.
Topics: Animals; Mice; Blood Platelets; Caspase 3; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Megakaryocytes; Purpura, Thrombocytopenic, Idiopathic; Thrombopoiesis
PubMed: 37573325
DOI: 10.1186/s12967-023-04389-9 -
Research and Practice in Thrombosis and... May 2023CD34 cells, megakaryocytes (MKs), and platelets express toll-like receptors (TLRs) that enable these cells to amplify the host innate immune response. However, the role...
BACKGROUND
CD34 cells, megakaryocytes (MKs), and platelets express toll-like receptors (TLRs) that enable these cells to amplify the host innate immune response. However, the role of TLR7/TLR8 activation in megakaryopoiesis has not yet been investigated.
OBJECTIVES
We evaluated the effect of coxsackievirus B3 (CVB3) and synthetic TLR7/TLR8 agonists on the development of human MKs and production of platelets.
METHODS
CD34 cells from human umbilical cord were inoculated with CVB3 or stimulated with synthetic TLR7/TLR8 agonists and then cultured in the presence of thrombopoietin.
RESULTS
CD34 cells, MK progenitor cells, and mature MKs expressed TLR7 and TLR8, and exposure to CVB3 resulted in productive infection, as determined by the presence of viral infectious particles in culture supernatants. Cell expansion, differentiation into MKs, MK maturation, and platelet biogenesis were significantly reduced in CD34-infected cultures. The reduction in MK growth was not due to an alteration in cellular proliferation but was accompanied by an increase in cellular apoptosis and pyroptosis. Impairment of MK generation and maturation of viable cells were also associated with decreased expression of transcription factors involved in these processes. These effects were completely abrogated by TLR7 but not TLR8 antagonists and mimicked by TLR7 but not TLR8 agonists. CVB3 infection of CD34 cells increased the immunophenotype of MKs characterized as CD148/CD48 or CD41/CD53 cells.
CONCLUSION
These data suggest a novel role of TLR7 in megakaryo/thrombopoiesis that may contribute to a better understanding of the molecular basis underlying thrombocytopenia and the immunologic role of MKs in viral infection processes.
PubMed: 37538496
DOI: 10.1016/j.rpth.2023.100184 -
Journal of Hematology & Oncology Jul 2023Hyperhomocysteinemia (HHcy) is closely associated with thrombotic diseases such as myocardial infarction and stroke. Enhanced platelet activation was observed in animals...
Hyperhomocysteinemia (HHcy) is closely associated with thrombotic diseases such as myocardial infarction and stroke. Enhanced platelet activation was observed in animals and humans with HHcy. However, the influence of HHcy on thrombopoiesis remains largely unknown. Here, we reported increased platelet count (PLT) in mice and zebrafish with HHcy. In hypertensive patients (n = 11,189), higher serum level of total Hcy was observed in participants with PLT ≥ 291 × 10/L (full adjusted β, 0.59; 95% CI 0.14, 1.04). We used single-cell RNA sequencing (scRNA-seq) to characterize the impact of Hcy on transcriptome, cellular heterogeneity, and developmental trajectories of megakaryopoiesis from human umbilical cord blood (hUCB) CD34 cells. Together with in vitro and in vivo analysis, we demonstrated that Hcy promoted megakaryocytes (MKs) differentiation via growth hormone (GH)-PI3K-Akt axis. Moreover, the effect of Hcy on thrombopoiesis is independent of thrombopoietin (TPO) because administration of Hcy also led to a significant increase of PLT in homozygous TPO receptor (Mpl) mutant mice and zebrafish. Administration of melatonin effectively reversed Hcy-induced thrombopoiesis in mice. ScRNA-seq showed that melatonin abolished Hcy-facilitated MK differentiation and maturation, inhibited the activation of GH-PI3K-Akt signaling. Our work reveals a previously unrecognized role of HHcy in thrombopoiesis and provides new insight into the mechanisms by which HHcy confers an increased thrombotic risk.Trial Registration clinicaltrials.gov Identifier: NCT00794885.
Topics: Humans; Mice; Animals; Thrombopoiesis; Megakaryocytes; Blood Platelets; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Zebrafish; Growth Hormone; Melatonin; Hyperhomocysteinemia; Cell Differentiation
PubMed: 37501059
DOI: 10.1186/s13045-023-01481-x -
International Journal of Biological... 2023Abnormal megakaryocyte maturation and platelet production lead to platelet-related diseases and impact the dynamic balance between hemostasis and bleeding. Cellular...
Abnormal megakaryocyte maturation and platelet production lead to platelet-related diseases and impact the dynamic balance between hemostasis and bleeding. Cellular repressor of E1A-stimulated gene 1 (CREG1) is a glycoprotein that promotes tissue differentiation. However, its role in megakaryocytes remains unclear. In this study, we found that CREG1 protein is expressed in platelets and megakaryocytes and was decreased in the platelets of patients with thrombocytopenia. A cytosine arabinoside-induced thrombocytopenia mouse model was established, and the mRNA and protein expression levels of CREG1 were found to be reduced in megakaryocytes. We established megakaryocyte/platelet conditional knockout () and transgenic mice (tg-). Compared to mice, mice exhibited thrombocytopenia, which was mainly caused by inefficient bone marrow (BM) thrombocytopoiesis, but not by apoptosis of circulating platelets. Cultured -megakaryocytes exhibited impairment of the actin cytoskeleton, with less filamentous actin, significantly fewer proplatelets, and lower ploidy. CREG1 directly interacts with MEK1/2 and promotes MEK1/2 phosphorylation. Thus, our study uncovered the role of CREG1 in the regulation of megakaryocyte maturation and thrombopoiesis, and it provides a possible theoretical basis for the prevention and treatment of thrombocytopenia.
Topics: Animals; Mice; Blood Platelets; Bone Marrow; Megakaryocytes; Mice, Transgenic; Thrombocytopenia; Thrombopoiesis; Humans
PubMed: 37496998
DOI: 10.7150/ijbs.78660