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At least 19 recordsLinked to original sources

PubMed1978

Hematopoiesis on cellulose ester membranes (CEM). II. Enrichment of the hematopoietic microenvironment by the addition of selected cellular elements.

Cellulose ester membranes (CEM) were folded into a trilaminar open-ended tube which was implanted into the peritoneal cavity of mice. CEM rapidly acquired a stromal core with many features of marrow such as fat, fibroblasts, an abundant sinusoidal microcirculation and monocyte-macrophage-like cells. CEM took up 59iron, 99technetium sulfur colloid and produced CSF in in vitro culture but their microenvironment supported only granulopoiesis. CEM were coated on their interior surfaces with bone marrow or regenerating medullary cavity mesenchyme or bone but the stromal cores supported only granulopoiesis after 3 weeks to 3 months of implantation. CEM coated with spleen and implanted into mice developed trilineal hematopoiesis within 6 weeks with abundant erythropoiesis and megakaryocytopoiesis in addition to granulopoiesis. These CEM differed from splenic tissue in that only scattered lymphoid tissue was present. CEM coated with bone marrow and bone developed trilineal hematopoiesis but only after3--6 months of peritoneal implantation. CEM coated with regenerating medullary cavity mesenchyme failed to develop trilineal hematopoiesis. Cyclophosphamide injection did not enhance hematopoiesis. These experiments indicate that splenic, marrow and bone tissue contain stromal elements capable of being transferred onto CEM which then develop a microenvironment capable of supporting trilineal hematopoiesis.

Animals↗

PubMed2026

IDH2 clonal hematopoiesis and IKAROS loss cooperate in a B-ALL subtype after lenalidomide therapy for multiple myeloma.

Lenalidomide, a maintenance treatment in multiple myeloma first-line therapy, increases the risk of secondary malignancies, including B-cell precursor acute lymphoblastic leukemia (B-ALL). We present a comprehensive molecular characterization of 57 patients with lenalidomide-associated B-ALL (LenB-ALL), revealing 3 mutational subgroups: (1) TP53mt (30%); (2) IDH2mt (p.R140Q) (23%); and (3) other, including NRAS/KRASmt. Remarkably, IDH2 R140Q mutations were highly enriched in LenB-ALL compared with those in primary B-ALL (P< .001). Furthermore, IKZF1 intragenic deletions, often subclonal and likely RAG recombinase-mediated, were observed in 54% (7/13) of IDH2mt patients with LenB-ALL. IDH2 mutations were not restricted to the leukemic clone: they persisted during measurable residual disease-negative remission and were identified in lymphoid as well as myeloid cell populations using fluorescence-activated cell sorting and single-cell RNA sequencing. This indicates a preleukemic origin of the IDH2 mutation within the context of clonal hematopoiesis. Transcriptomic and DNA methylation analyses revealed a distinct gene expression profile and a DNA hypermethylation phenotype in IDH2mt LenB-ALL, including IDH2mt-specific as well as lenalidomide-associated features. We propose that lenalidomide promotes the expansion of IDH2-mutated clonal hematopoiesis and, via IKAROS downregulation, induces a maturation arrest at the B-cell precursor stage. Subsequent genetic or epigenetic alterations render leukemogenesis independent of ongoing lenalidomide exposure. All these data define IDH2mt B-ALL as a distinct molecular subtype that is markedly overrepresented after lenalidomide treatment and highlight clonal hematopoiesis as a key contributing factor in the development of LenB-ALL.

Humans↗

PubMed1977

Extramedullary hematopoiesis in Paget's disease of bone.

Two cases of Paget's disease of bone with radiographic manifestation of extramedullary hematopoiesis are described. While extramedullary hematopoiesis usually occurs as compensatory phenomenon in response to anemia, this was not the case in our patients. We believe pathologic fractures led to extrusion of hematopoietic marrow and resultant tumorous extramedullary hematopoiesis.

Aged↗

PubMed1979

Prolonged hematopoiesis in a primate bone marrow culture system: characteristics of stem cell production and the hematopoietic microenvironment.

Maintenance of myelopoiesis and pluripotential stem cell production for prolonged periods in vitro hitherto has been limited to mouse bone marrow culture. In an effort to adapt the system for use in higher species, particularly in human and non-human primates, studies were undertaken using the prosimian species, Tupaia glis (tree shrew). In a number of experiments the duration of sustained normal hematopoiesis observed in cultures of this species, following a single inoculum of 5 X 10(6)--10(7) bone marrow cells, with or without addition of fresh allogeneic bone marrow exceeded 1 yr. Analysis of suspension cells obtained by weekly demidepopulation of such cultures revealed production of CFU-C, differentiating neutrophils, and basophils at high levels. Direct comparison with murine cultures indicated that in both species a complex series of cellular interactions takes place within an adherent environment of marrow-derived endothelial cells, macrophages, and fat-containing cells. Certain functional and ultrastructural features served to distinguish murine from Tupaia marrow cultures, and the prolonged duration of in vitro hematopoiesis in the latter species could be attributed to a regenerative capacity possessed by its adherent hematopoietic microenvironment. The availability of this primate marrow culture system should facilitate studies of hematopoiesis, viral leukemogenesis, and transplantation biology, which have more direct relevance to man than that provided by the existing murine system.

Animals↗

PubMed1977

Amphotericin inhibition of hematopoiesis in vitro.

The effect of amphotericin B on human and murine hematopoiesis was studied in vitro using assays for erythroid and myeloid colony-forming cells. Amphotericin consistently inhibited colony formation by erythroid and granulocyte-monocyte progenitor cells. Clear effects were observable at amphotericin concentrations of 1.0 microgram/ml, and concentrations of 2.0 microgram/ml caused approximately 50-60% inhibition of cloning of both murine and normal human bone marrow. These data suggest that amphotericin, in concentrations achieved in therapy, can impair hematopoiesis by a direct effect on precursor cells.

Amphotericin B↗

PubMed2026

Mediator at the Helm: Coordinating transcription and biomolecular condensates in hematopoiesis.

Hematopoiesis relies on precisely coordinated transcriptional programs that balance stem cell self-renewal, lineage commitment, and terminal differentiation. Central to this regulation is the Mediator complex, a large multi-subunit transcriptional co-regulator that integrates signals from transcription factors and chromatin regulators to control RNA polymerase Ⅱ (Pol Ⅱ) activity. The dynamic and modular composition of Mediator enables context-dependent transcriptional outputs, while individual subunits can exert specialized regulatory functions during hematopoietic lineage specification, thereby contributing to cell-fate-specific transcriptional outputs. Recent advances further reveal that transcriptional regulation is shaped by the spatial organization of regulatory machinery with biomolecular condensates formed through liquid-liquid phase separation (LLPS), particularly at super-enhancers. In this emerging framework, Mediator functions not only as a transcriptional integrator but also as a key coordinator of transcriptional machinery within condensates at cell-fate-related gene loci. In this chapter, we summarize how distinct Mediator subunits confer specific modes of transcriptional regulation and discuss how the interplay between Mediator and phase-separated condensates shapes transcriptional control during hematopoiesis. We highlight how specific subunits, including MED1 and MED26, participate in distinct regulatory modes in erythropoiesis, spanning super-enhancer-driven transcriptional activation, progenitor expansion, and condensate-associated mechanisms that influence Pol Ⅱ pausing and global transcription repression during terminal differentiation. Together, these findings support a model in which Mediator integrates transcriptional regulation with nuclear organization through condensate-mediated mechanisms, providing a conceptual framework for understanding hematopoietic cell fate decisions and transcriptional dysregulation in hematological diseases.

Hematopoiesis↗

PubMed2025

Transcriptional activation of regenerative hematopoiesis via microenvironmental sensing.

Transition between activation and quiescence states in hematopoietic stem and progenitor cells (HSPCs) is tightly governed by cell-intrinsic means and microenvironmental co-adaptation. Although this balance is fundamental for lifelong hematopoiesis and immunity, the underlying molecular mechanisms remain poorly defined. Multimodal analysis divulging differential transcriptional activity between distinct HSPC states indicates the presence of Fli-1 transcription factor binding motif in activated hematopoietic stem cells. We reveal that Fli-1 activity is essential during regenerative hematopoiesis in mice. Fli-1 directs activation programs while priming cellular sensory and output machineries, enabling HSPCs co-adoptability with a stimulated vascular niche through propagation of niche-derived angiocrine Notch1 signaling. Constitutively induced Notch1 signaling is sufficient to recuperate functional hematopoietic stem cells impairments in the absence of Fli-1, without leukemic transformation. Applying FLI-1 transient modified-mRNA transduction into latent adult human mobilized HSPCs, enables their niche-mediated expansion and superior engraftment capacities. Thus, decryption of stem cell activation programs offers valuable insights for immunological regenerative medicine.

Animals↗

PubMed2026

Impaired Glycolysis Leads to Defective Efferocytosis and Impaired Plaque Resolution in Tet2 Clonal Hematopoiesis.

BACKGROUND: Clonal hematopoiesis (CH) arising from mutations in hematopoietic genes has been identified as an important risk factor for atherosclerotic cardiovascular disease. Despite the established role of some CH mutations in promoting atherosclerosis progression, their role in clinically relevant LDL (low-density lipoprotein) lowering-induced plaque remodeling or regression has not been extensively studied. METHODS: To assess the effects of TET2 (tet methylcytosine dioxygenase 2) CH on plaque resolution, we prepared control or chimeric Tet2+/- CH mice with conditional deletion of Tet2 in hematopoietic stem cells during LDL lowering-induced plaque remodeling. After establishing atherosclerosis by Western diet feeding for 12 weeks in Ldlr-/- mice, Tet2 was deleted by tamoxifen injection, and hypercholesterolemia was either normalized to simulate clinical lipid management, or mice were continued on the Western diet. RESULTS: Unlike control mice, Tet2+/- CH mice failed to significantly reduce necrotic core area or increase fibrous cap thickness and showed impaired macrophage efferocytosis during LDL lowering. Single-cell RNA sequencing and gene set enrichment analysis of aortic cell populations revealed that Tet2 deficient monocyte/macrophage populations were defective in glycolysis, phagocytosis, and actin polymerization. Tet2-deficient bone marrow-derived macrophages and Tet2+/- induced pluripotent stem cell-derived human macrophages showed defective ability to sustain continuing rounds of efferocytosis. Bone marrow-derived macrophages displayed reduced apoptotic cell binding and internalization and impaired activity of Wiskott-Aldrich syndrome protein and SCAR (suppressor of cyclic AMP receptor) homolog complex mediated actin polymerization. We linked these defects to reduced anaerobic glycolysis and lactate levels and rescued them by lactate supplementation or by treatment with the HIF-1α (hypoxia-inducible factor 1α) activator molidustat. Molidustat treatment reversed the defects in necrotic core and fibrous cap formation during LDL lowering-induced plaque remodeling in Tet2+/- CH mice. Reduced plasma lactate levels were also shown in TET2 clonal hematopoiesis of indeterminate potential carriers in the UK Biobank. CONCLUSIONS: Our data identify impaired efferocytosis and glycolysis-lactate-actin polymerization pathways in advanced atherosclerosis as potential therapeutic targets to induce proresolving restructuring of the plaque immune cells and to promote beneficial atherosclerosis remodeling in subjects with TET2 CH.

LDL lowering↗

PubMed1979

Cyclic hematopoiesis. Effects of endotoxin on colony-forming cells and colony-stimulating activity in grey collie dogs.

Cyclic changes in blood neutrophil counts of grey collie dogs with cyclic hematopoiesis can be eliminated by daily endotoxin injections. Studies were performed to determine the mechanism whereby endotoxin alters this disease. Bone marrow granulocyte-macrophage progenitor cells (colony-forming cells [CFUc]) showed cyclic variation in the untreated grey collie, which was eliminated by chronic endotoxin treatment (Salmonella typhosa lipopolysaccharide W, 5 microgram/kg per day). Similar cyclic variation in blood CFUc was eliminated by this treatment. Tritiated thymidine suicide of the marrow colony-forming cells failed to show cyclic changes to explain the marked swing in CFUc numbers in untreated grey collies. The thymidine suicide rates were not significantly changed by chronic endotoxin treatment. Similarly, serum colony-stimulating activity did not show cyclic variation with the cyclic neutrophil counts in untreated grey collies and was not altered by chronic endotoxin treatment. We suggest that endotoxin eliminates neutrophil cycling in cyclic hematopoiesis by a direct effect on the flux of pluripotent stem cells into the committed stem cell compartment and that this occurs independent of changes in serum colony-stimulating activity.

Animals↗

PubMed1979

Hematopoiesis of hereditarily asplenic-athymic (lasat) mice.

The hematopoiesis of athymic-asplenic (lasat) mice was compared with that of normal, asplenic, and athymic littermates with the same strain background. Erythrocyte blood volume, number and survival time were normal when related to the body weight of the animals. Peripheral blood showed leukopenia with absolute and relative lymphopenia, resembling the athymic rather than the asplenic pattern. The bone marrow was hypocellular as a consequence of a decrease in both lymphocytes and erythroid precursors, while thrombocytopoiesis and granulcytopoiesis-monocytopoiesis were essentially normal. Although the percentile value of femoral stem cells was high, their absolute number was, in fact, reduced by 35% as a result of the bone marrow hypocellularity. When lasat bone marrow cells were injected into normal, lethally irradiated mice, a rapid erythropoietic recovery was observed, whereas the restoration of the granlocytic compartment was impaired. It was concluded that: 1) lasat mice depict a normal hematopoiesis in spite of the congenital absence of the thymus and the spleen; 2) bone marrow stem cells may be defective when administered to lethally irradiated hosts; and 3) the athymic status predominates over the asplenic one.

Animals↗

PubMed1977

Anemia and extramedullary hematopoiesis associated with carcinoma of the breast.

Three patients with carcinoma of the breast, extensive metastasis, and splenomegaly are described. Radioisotope studies with 59Fe and 51Cr revealed extramedullarly hematopoiesis and hemolysis. In addition to red cell hemolysis, ineffective erythropoiesis in the marrow and extramedullary sites contributed to the persistence of the anemic syndrome. Extramedullary hematopoiesis is not an effective compensatory mechanism in some patients with anemia and carcinoma of the breast.

Adult↗

PubMed2026

The landscape of clonal hematopoiesis of indeterminate potential in long-term breast cancer survivors.

BACKGROUND: Clonal hematopoiesis of indeterminate potential (CHIP) can confound blood-based genomics and may be shaped by cytotoxic therapy; clarifying its persistence after breast-cancer chemotherapy is relevant for long-term survivorship follow-up. PATIENTS AND METHODS: Buffy-coat whole-exome sequencing was performed in 189 stage I-III breast-cancer survivors with blood collected a median 136.5 months after diagnosis. CHIP was assessed using a prespecified 100-gene hematopoietic-driver compendium and exome-wide interrogation. Clinical associations were assessed with univariable tests and multivariable logistic regression including chemotherapy, radiotherapy, age, smoking and obesity. RESULTS: Within the 100-gene compendium, 54/189 (28.6%) patients harbored ≥1 variant, predominantly missense, with DNMT3A and TET2 predominating and multi-hit cases rare. In multivariable models, chemotherapy was not associated with panel-defined CHIP (OR 0.77; 95% CI 0.40-1.48; p = 0.432). Similarly, age, adjuvant radiotherapy, obesity and smoking status were not significantly associated with panel-defined CHIP. Gene-level comparisons showed no differences by chemotherapy exposure. Exome-wide, 67/189 (35.4%) patients carried ≥1 variant; chemotherapy was not associated with exome-wide variant positivity (OR 0.89; 95% CI 0.48-1.67; p = 0.721), and no locus differed between chemotherapy-exposed and never-exposed women. CONCLUSION: Buffy-coat WES performed in long-term breast cancer survivors shows no cohort-level association between prior chemotherapy and increased CHIP.

Humans↗

PubMed2025

Colchicine and Longitudinal Dynamics of Clonal Hematopoiesis: An Exploratory Substudy of the LoDoCo2 Trial.

BACKGROUND: Clonal hematopoiesis (CH) is an aging-related hematologic condition associated with increased risk for cardiovascular events. Larger CH clones associate more strongly with cardiovascular risk. Preclinical data indicate that inflammatory signaling drives expansion of CH clones and CH-associated cardiovascular disease. However, the effect of anti-inflammatory therapies on CH clonal dynamics in humans is unclear. OBJECTIVES: The goal of this study was to test the association of randomization to colchicine vs placebo with CH growth in participants with chronic coronary artery disease. It also assessed the association of colchicine use with change in inflammatory biomarkers over time according to CH status. METHODS: In this exploratory substudy of the LoDoCo2 (Low-Dose Colchicine 2) trial, high-coverage targeted sequencing was used to detect CH driver mutations and to quantify variant allele frequency at 4 timepoints: baseline, after a 30-day open-label colchicine run-in phase (0.5 mg daily), 1 year postrandomization to colchicine or placebo, and at end of study (median follow-up of 25.0 months). Clonal dynamics were assessed by using a generalized linear mixed model. High-sensitivity C-reactive protein and interleukin-6 were additionally measured at baseline, randomization, and 1 year postrandomization. RESULTS: In total, 854 participants contributed 2,047 observations across 4 timepoints, including before and after the prerandomization colchicine run-in period. Randomization to placebo was associated with a 14.9% annual increase in CH clone size (βtime = 0.14; 95% CI: 0.08 to 0.21) vs a nonsignificant 6.3% increase with colchicine (βtime on colchicine: 0.06; 95% CI: -0.01 to 0.14), although this difference between treatment arms was not statistically significant (Pinteraction = 0.13). Compared with placebo, colchicine was associated with attenuated clonal growth in TET2 CH (βtime on colchicine: 0.09 [95% CI: -0.04 to 0.22]; βtime placebo: 0.27 [95% CI: 0.16 to 0.37]; Pinteraction= 0.04). Among individuals with non-DNMT3A CH, interleukin-6 levels increased to a lesser extent in those receiving colchicine vs placebo over 1 year (30.0% vs 98.1% increase, respectively; Pinteraction = 0.01). CONCLUSIONS: In this exploratory analysis, treatment with low-dose colchicine was associated with attenuated clonal expansion in TET2 CH. These findings suggest the potential for colchicine to curb the proliferative advantage of key CH driver mutations and to mitigate their associated risk of cardiovascular disease. Further validation in prospective studies is warranted.

Humans↗

PubMed2026

Splenic extramedullary hematopoiesis in myelofibrosis is shaped by transcriptomic and epigenetic dysregulation.

Myelofibrosis (MF) is a chronic, progressive myeloproliferative neoplasm characterized by bone marrow fibrosis, ineffective blood cell production, and neoplastic extramedullary hematopoiesis (EMH) occurring primarily within the spleen. To explore the molecular mechanisms underlying splenic EMH, we performed single-cell transcriptional and chromatin profiling of cells from MF spleens that had been surgically removed. We demonstrate significant expansion of hematopoietic stem and progenitor cells, coupled with aberrant differentiation toward the erythroid and megakaryocytic lineages, associated with a significant enrichment of inflammatory pathways with enhanced NF-κB signaling and IFN responses, as well as dysregulation of the inferred function of differentiation-defining transcription factors. Finally, we report a significant remodeling of the immune microenvironment in MF spleens, characterized by emergence of dysfunctional T cell subsets and inflammatory memory B cells, suggesting the concomitant establishment of a pro-inflammatory and immune-tolerant tumor microenvironment within the spleen that influences hematopoietic cell differentiation and impairs tumor immune surveillance.

Primary Myelofibrosis↗

PubMed2025

Clonal Hematopoiesis and Risk of New-Onset Myocarditis and Pericarditis.

IMPORTANCE: Clonal hematopoiesis of indeterminate potential (CHIP) is the age-related clonal expansion of hematopoietic stem cells with leukemia-associated mutations. Certain CHIP mutations promote atherosclerosis and heart failure through immune-related pathways. OBJECTIVE: To test whether CHIP is associated with the development of myocarditis and pericarditis. DESIGN, SETTING, AND PARTICIPANTS: This observational population-based cohort study used data from the UK Biobank. Enrollment occurred between 2006 and 2010. Participants with whole-exome sequencing, no prevalent cardiovascular disease or hematological malignancy, and complete covariate data were included. Follow-up occurred for a median of 13.6 (IQR, 12.8-14.2) years. Analyses were conducted from November 2024 to July 2025. EXPOSURES: Any CHIP (variant allele frequency [VAF] ≥2%) and large CHIP (VAF ≥10%) constituted coprimary study exposures. Secondary analyses considered DNMT3A and TET2 CHIP as separate exposures. MAIN OUTCOMES AND MEASURES: The primary outcome was a composite of incident myocarditis and pericarditis. Cox regression tested associations of CHIP with myocarditis and pericarditis, adjusting for age, sex, race and ancestry, and cardiovascular risk factors. Secondary analyses considered myocarditis and pericarditis as separate outcomes. Additional analyses compared associations of CHIP with myocarditis and pericarditis with those with other cardiovascular diseases, and tested the bidirectional associations between CHIP and noncardiac immune-mediated inflammatory diseases. RESULTS: Among 335 426 participants (mean age, 56.1 years; 185 429 female [55.3%] and 149 997 male [44.7%]), 11 057 had any CHIP (3.3%), 7271 had large CHIP (2.2%), and 382 developed myocarditis or pericarditis (0.11%). Any and large CHIP were associated with multivariable-adjusted hazard ratios of 1.75 (95% CI, 1.14-2.68; P = .01) and 2.07 (95% CI, 1.28-3.33; P = .003), respectively, for the primary composite outcome of incident myocarditis and pericarditis. Increased risks were observed for DNMT3A and TET2 CHIP, with hazard ratios of 2.22 (95% CI, 1.17-4.21; P = .01) for DNMT3A with pericarditis and 3.65 (95% CI, 1.16-11.49; P = .03) for TET2 with myocarditis. CHIP associated with myocarditis and pericarditis more strongly than with other cardiovascular diseases (eg, coronary artery disease and heart failure). Any CHIP was also associated with 1.27-fold risk (95% CI, 1.16-1.39; P < .001) of developing noncardiac immune-mediated inflammatory diseases, without evidence for reverse causation. CONCLUSIONS AND RELEVANCE: In this study, CHIP was a strong risk factor for myocarditis and pericarditis among middle-aged adults. Targeting CHIP and its downstream pathways may represent a strategy for preventing or treating pericarditis and myocarditis.

Adult↗

PubMed2026

Clonal Hematopoiesis and Incident Heart Failure.

IMPORTANCE: Clonal hematopoiesis of indeterminate potential (CHIP), the age-related clonal expansion of hematopoietic cells with acquired preleukemic variants, has been associated with cardiometabolic diseases, including heart failure (HF). However, prior studies have lacked power to examine less common CHIP driver variants and have not investigated potential mediators of the CHIP-HF association. OBJECTIVE: To test whether specific CHIP subtypes are associated with incident HF and determine the extent to which CHIP-associated comorbidities mediate this association. DESIGN, SETTING, AND PARTICIPANTS: This was a UK Biobank prospective population-based cohort study of community-dwelling adults in the UK, with enrollment from 2006 to 2010 and follow-up through 2020. Included were participants with whole-exome sequencing (WES) and without prevalent HF, hematologic malignancy, or other CHIP-associated comorbidities (coronary artery disease [CAD], atrial fibrillation [AF], type 2 diabetes [T2D], or chronic kidney disease [CKD]) at baseline. Study data were analyzed from April through October 2025. EXPOSURES: Presence of CHIP and gene-specific CHIP subtypes (DNMT3A, non-DNMT3A, TET2, ASXL1, JAK2, DNA damage repair genes, and spliceosome genes). Mediation analyses examined CHIP-associated comorbidities (CAD, AF, T2D, and CKD). MAIN OUTCOMES AND MEASURES: The primary outcome was incident HF. Cox regression tested associations of CHIP and CHIP subtypes with incident HF, adjusted for age, sex, race, and cardiovascular risk factors. RESULTS: Among 417 616 participants (mean [SD] age, 56.1 [8.1] years; 234 868 female [56.2%]), 7183 (1.7%) developed incident HF over a median (IQR) of 11.1 (10.4-11.8) years of follow-up. CHIP was associated with HF risk (adjusted hazard ratio [aHR], 1.27; 95% CI, 1.15-1.40; P < .001), driven by non-DNMT3A subtypes (aHR, 1.52; 95% CI, 1.33-1.75; P < .001), including associations with TET2, ASXL1, JAK2, and spliceosome CHIP. DNMT3A CHIP was more modestly associated with HF (aHR, 1.15; 95% CI, 1.00-1.31; P = .04). In mediation analyses, development of CAD, AF, T2D, and/or CKD collectively accounted for 28.2% of the association (95% CI, 11.6%-45.4%; P = .001) between non-DNMT3A CHIP and HF. CONCLUSIONS AND RELEVANCE: Results of this cohort study suggest that CHIP, especially non-DNMT3A CHIP, was associated with incident HF. Other CHIP-associated comorbidities explained only a minority of the association between non-DNMT3A CHIP and HF. These findings suggest that CHIP is an HF risk factor and potential therapeutic target.

Adult↗

PubMed1979

Cardiac tamponade resulting from pericardial extramedullary hematopoiesis: a case report and review of the literature.

A patient with an unusual myeloproliferative disorder, characterized by hepatosplenomegaly, myelofibrosis, ringed sideroblasts, and conversion to acute myeloblastic leukemia developed cardiac tamponade secondary to pericardia extramedullary hematopoiesis. Diagnostic criteria are discussed. Irradiation and systemic chemotherapy were successful in controlling the effusion.

Adolescent↗

PubMed2026

Tropomyosin 1 Promotes Platelet Adhesion and Clot Contraction Separate from Its Roles in Developmental Hematopoiesis.

Genome-wide association studies (GWAS) link the Tropomyosin 1 (Tpm1) locus to quantitative blood trait variation, but related mechanisms are unclear. Tpm1 encodes an actin-binding protein that regulates actin filament diversity, cell adhesion, signaling, and actomyosin contractility. Murine Tpm1 deficiency enhances hemogenic endothelial cell (HEC) specification, but it was unclear if these effects extended to postnatal hematopoiesis. We used Cdh5Cre and VavCre models to conditionally knock out Tpm1 (Tpm1KO) in endothelial anor hematopoietic cells. Both models ablate Tpm1 in postnatal blood. Endothelial Tpm1KO increases HEC specification without altering hematopoietic progenitor cell production or adult blood counts, suggesting separate roles for Tpm1 in the embryonic and adult blood systems. Tpm1KO increases adult platelet lifespan and diminishes adhesion to fibronectin and fibrinogen. Chemical Tpm1 inhibition also reduces focal adhesion in murine and human platelets. Altered platelet morphology and reduced platelet spreading suggest perturbed actomyosin contractility underlies these findings. Platelet fibrin binding promotes blood clot contraction, which reduces occlusive thrombosis. Tpm1KO limits clot contraction and worsens vascular occlusion in ferric chloride-induced stroke models. In addition to offering a mechanistic explanation for why genetic variation at the TPM1 alters platelet traits in GWAS, our findings reveal novel roles for Tpm1 in clot contraction and thrombosis.

Animals↗