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Journal of Thrombosis and Haemostasis :... Nov 2023Glucocorticoids are widely known for their immunomodulatory action. Their synthetic analogs are used to treat several autoimmune diseases, including immune...
BACKGROUND
Glucocorticoids are widely known for their immunomodulatory action. Their synthetic analogs are used to treat several autoimmune diseases, including immune thrombocytopenia. However, their efficacy and mechanisms of action in immune thrombocytopenia are not fully understood.
OBJECTIVES
To investigate the mechanism of glucocorticoid actions on platelet production.
METHODS
The actions of glucocorticoids on platelet production were studied combining in vivo, ex vivo and in vitro approaches.
RESULTS
Dexamethasone reduced bleeding in mice and rapidly increased circulating young platelet counts. In vitro glucocorticoid treatment stimulated proplatelet formation by megakaryocytes and platelet-like particle release. This effect was blocked by glucocorticoid receptor antagonist RU486, indicating a glucocorticoid receptor-dependent mechanism. Genome-wide analysis revealed that dexamethasone regulates the expression of >1000 genes related to numerous cellular functions, including predominant cytoplasm and cytoskeleton reorganization. Dexamethasone and other glucocorticoids induced the expression of Gda (the gene encoding guanine deaminase), which has been reported to have a role in dendrite development. Inhibition of guanine deaminase enzymatic activity blocked dexamethasone stimulation of proplatelet formation, implicating a critical role for this enzyme in glucocorticoid-mediated platelet production.
CONCLUSION
Our findings identify glucocorticoids as new regulators of thrombopoiesis.
Topics: Mice; Animals; Megakaryocytes; Thrombopoiesis; Glucocorticoids; Purpura, Thrombocytopenic, Idiopathic; Receptors, Glucocorticoid; Guanine Deaminase; Transcriptome; Blood Platelets; Thrombocytopenia; Dexamethasone
PubMed: 37336437
DOI: 10.1016/j.jtha.2023.06.012 -
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 -
Blood Jan 2024
Topics: Bone Marrow; Megakaryocytes; Thrombopoiesis; Erythrocyte Membrane; Lung
PubMed: 38236613
DOI: 10.1182/blood.2023022897 -
Journal of Thrombosis and Haemostasis :... Sep 2023Germline mutations in the ETV6 transcription factor gene are responsible for familial thrombocytopenia and leukemia predisposition syndrome. Although previous studies...
BACKGROUND
Germline mutations in the ETV6 transcription factor gene are responsible for familial thrombocytopenia and leukemia predisposition syndrome. Although previous studies have shown that ETV6 plays an important role in megakaryocyte (MK) maturation and platelet formation, the mechanisms by which ETV6 dysfunction promotes thrombocytopenia remain unclear.
OBJECTIVES
To decipher the transcriptional mechanisms and gene regulatory network linking ETV6 germline mutations and thrombocytopenia.
METHODS
Presuming that ETV6 mutations result in selective effects at a particular cell stage, we applied single-cell RNA sequencing to understand gene expression changes during megakaryopoiesis in peripheral CD34 cells from healthy controls and patients with ETV6-related thrombocytopenia.
RESULTS
Analysis of gene expression and regulon activity revealed distinct clusters partitioned into 7 major cell stages: hematopoietic stem/progenitor cells, common-myeloid progenitors (CMPs), MK-primed CMPs, granulocyte-monocyte progenitors, MK-erythroid progenitors (MEPs), progenitor MKs/mature MKs, and platelet-like particles. We observed a differentiation trajectory in which MEPs developed directly from hematopoietic stem/progenitor cells and bypassed the CMP stage. ETV6 deficiency led to the development of aberrant cells as early as the MEP stage, which intensified at the progenitor MK/mature MK stage, with a highly deregulated core "ribosome biogenesis" pathway. Indeed, increased translation levels have been documented in patient CD34-derived MKs with overexpression of ribosomal protein S6 and phosphorylated ribosomal protein S6 in both CD34-derived MKs and platelets. Treatment of patient MKs with the ribosomal biogenesis inhibitor CX-5461 resulted in an increase in platelet-like particles.
CONCLUSION
These findings provide novel insight into both megakaryopoiesis and the link among ETV6, translation, and platelet production.
Topics: Humans; Cell Differentiation; Megakaryocytes; Ribosomal Protein S6; Single-Cell Analysis; Thrombocytopenia; Thrombopoiesis; Antigens, CD34; ETS Translocation Variant 6 Protein
PubMed: 37085035
DOI: 10.1016/j.jtha.2023.04.007 -
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 -
Critical shifts in lipid metabolism promote megakaryocyte differentiation and proplatelet formation.Nature Cardiovascular Research Sep 2023During megakaryopoiesis, megakaryocytes (MK) undergo cellular morphological changes with strong modification of membrane composition and lipid signaling. Here we adopt a...
During megakaryopoiesis, megakaryocytes (MK) undergo cellular morphological changes with strong modification of membrane composition and lipid signaling. Here we adopt a lipid-centric multiomics approach to create a quantitative map of the MK lipidome during maturation and proplatelet formation. Data reveal that MK differentiation is driven by an increased fatty acyl import and lipid synthesis, resulting in an anionic membrane phenotype. Pharmacological perturbation of fatty acid import and phospholipid synthesis blocked membrane remodeling and directly reduced MK polyploidization and proplatelet formation resulting in thrombocytopenia. The anionic lipid shift during megakaryopoiesis was paralleled by lipid-dependent relocalization of the scaffold protein CKIP-1 and recruitment of the kinase CK2α to the plasma membrane, which seems to be essential for sufficient platelet biogenesis. Overall, this study provides a framework to understand how the MK lipidome is altered during maturation and the impact of MK membrane lipid remodeling on MK kinase signaling involved in thrombopoiesis.
PubMed: 38075556
DOI: 10.1038/s44161-023-00325-8 -
Thrombosis Journal Oct 2023Immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disease characterized by increased platelet destruction and impaired thrombopoiesis. The changes in platelet...
BACKGROUND
Immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disease characterized by increased platelet destruction and impaired thrombopoiesis. The changes in platelet indices depend on the morphology and volume of platelets. Serum lipids have been found to affect platelet formation and activity in certain diseases, thus inducing the corresponding variation of platelet indices.
METHODS
Mendelian randomization (MR) analysis was performed based on databases. The clinical data from 457 ITP patients were retrospectively collected and analyzed, including platelet indices, serum lipids, hemorrhages and therapeutic responses.
RESULTS
MR analysis showed low high-density-lipoprotein-cholesterol (HDL-C), low apolipoprotein A-1, high triglyceride (TG) and high apolipoprotein B (ApoB) caused high platelet distribution width (PDW); high low-density-lipoprotein-cholesterol (LDL-C) increased mean platelet volume (MPV). In ITP, there were positive correlations between platelet count with TG, PDW with HDL-C and ApoB, and plateletcrit with TG and non-esterified fatty acid, and the correlation had gender differences. Bleeding scores were negatively correlated with cholesterol and LDL-C. LDL-C and homocysteine were risk factors for therapeutic responses.
CONCLUSIONS
Serum lipids, especially cholesterol were tightly correlated with platelet indices, hemorrhage and therapeutic effects in ITP patients. These results provide clinical references for the management of serum lipids, and highlight the necessity to further explore the relationship between lipids and pathogenesis of ITP.
TRIAL REGISTRATION
No: NCT05095896, October 14, 2021, retrospectively registered.
PubMed: 37833799
DOI: 10.1186/s12959-023-00551-x -
Nature Communications Nov 2023Circulating cell-free DNA (cfDNA) fragments are a biological analyte with extensive utility in diagnostic medicine. Understanding the source of cfDNA and mechanisms of...
Circulating cell-free DNA (cfDNA) fragments are a biological analyte with extensive utility in diagnostic medicine. Understanding the source of cfDNA and mechanisms of release is crucial for designing and interpreting cfDNA-based liquid biopsy assays. Using cell type-specific methylation markers as well as genome-wide methylation analysis, we determine that megakaryocytes, the precursors of anuclear platelets, are major contributors to cfDNA (~26%), while erythroblasts contribute 1-4% of cfDNA in healthy individuals. Surprisingly, we discover that platelets contain genomic DNA fragments originating in megakaryocytes, contrary to the general understanding that platelets lack genomic DNA. Megakaryocyte-derived cfDNA is increased in pathologies involving increased platelet production (Essential Thrombocythemia, Idiopathic Thrombocytopenic Purpura) and decreased upon reduced platelet production due to chemotherapy-induced bone marrow suppression. Similarly, erythroblast cfDNA is reflective of erythrocyte production and is elevated in patients with thalassemia. Megakaryocyte- and erythroblast-specific DNA methylation patterns can thus serve as biomarkers for pathologies involving increased or decreased thrombopoiesis and erythropoiesis, which can aid in determining the etiology of aberrant levels of erythrocytes and platelets.
Topics: Humans; Megakaryocytes; Thrombopoiesis; Erythropoiesis; Cell-Free Nucleic Acids; Blood Platelets; Erythroblasts; DNA
PubMed: 37985773
DOI: 10.1038/s41467-023-43310-2 -
Cells Dec 2023The bone marrow (BM) hematopoietic system (HS) gives rise to blood cells originating from hematopoietic stem cells (HSCs), including megakaryocytes (MKs) and red blood...
The bone marrow (BM) hematopoietic system (HS) gives rise to blood cells originating from hematopoietic stem cells (HSCs), including megakaryocytes (MKs) and red blood cells (erythrocytes; RBCs). Many steps of the cell-fate decision remain to be elucidated, being important for cancer treatment. To explore the role of Wnt/β-catenin for MK and RBC differentiation, we activated β-catenin signaling in platelet-derived growth factor b (Pdgfb)-expressing cells of the HS using a Cre-lox approach (Ctnnb1). FACS analysis revealed that Pdgfb is mainly expressed by megakaryocytic progenitors (MKPs), MKs and platelets. Recombination resulted in a lethal phenotype in mutants (Ctnnb1, Ctnnb1) 3 weeks after tamoxifen injection, showing an increase in MKs in the BM and spleen, but no pronounced anemia despite reduced erythrocyte counts. BM transplantation (BMT) of Ctnnb1 BM into lethally irradiated wildtype recipients (BMT-Ctnnb1) confirmed the megakaryocytic, but not the lethal phenotype. CFU-MK assays in vitro with BM cells of Ctnnb1 mice supported MK skewing at the expense of erythroid colonies. Molecularly, the runt-related transcription factor 1 (RUNX1) mRNA, known to suppress erythropoiesis, was upregulated in Ctnnb1 BM cells. In conclusion, β-catenin activation plays a key role in cell-fate decision favoring MK development at the expense of erythroid production.
Topics: Animals; Mice; beta Catenin; Megakaryocyte-Erythroid Progenitor Cells; Megakaryocytes; Proto-Oncogene Proteins c-sis; Thrombopoiesis
PubMed: 38067194
DOI: 10.3390/cells12232765