Neutropenia is probably the strongest known predisposition to infection with otherwise harmless environmental or microbiota-derived species. Because initial swarming of neutrophils at the site of ...infection occurs within minutes, rather than the hours required to induce "emergency granulopoiesis," the relevance of having high numbers of these cells available at any one time is obvious. We observed that germ-free (GF) animals show delayed clearance of an apathogenic bacterium after systemic challenge. In this article, we show that the size of the bone marrow myeloid cell pool correlates strongly with the complexity of the intestinal microbiota. The effect of colonization can be recapitulated by transferring sterile heat-treated serum from colonized mice into GF wild-type mice. TLR signaling was essential for microbiota-driven myelopoiesis, as microbiota colonization or transferring serum from colonized animals had no effect in GF MyD88(-/-)TICAM1(-/-) mice. Amplification of myelopoiesis occurred in the absence of microbiota-specific IgG production. Thus, very low concentrations of microbial Ags and TLR ligands, well below the threshold required for induction of adaptive immunity, sets the bone marrow myeloid cell pool size. Coevolution of mammals with their microbiota has probably led to a reliance on microbiota-derived signals to provide tonic stimulation to the systemic innate immune system and to maintain vigilance to infection. This suggests that microbiota changes observed in dysbiosis, obesity, or antibiotic therapy may affect the cross talk between hematopoiesis and the microbiota, potentially exacerbating inflammatory or infectious states in the host.
The mammalian microbiota is a recently recognized regulator of hematopoiesis. In this issue of Cell Stem Cell, Zhang et al. (2022) show in mice that microbiota-derived butyrate enhances bone marrow ...macrophage erythrophagocytosis-dependent iron availability, which supports stress-induced hematopoietic stem cell differentiation and blood regeneration.
The mammalian microbiota is a recently recognized regulator of hematopoiesis. In this issue of Cell Stem Cell, Zhang et al. (2022) show in mice that microbiota-derived butyrate enhances bone marrow macrophage erythrophagocytosis-dependent iron availability, which supports stress-induced hematopoietic stem cell differentiation and blood regeneration.
Understanding human hematopoietic stem cell fate control is important for its improved therapeutic manipulation. Asymmetric cell division, the asymmetric inheritance of factors during division ...instructing future daughter cell fates, was recently described in mouse blood stem cells. In human blood stem cells, the possible existence of asymmetric cell division remained unclear because of technical challenges in its direct observation. Here, we use long-term quantitative single-cell imaging to show that lysosomes and active mitochondria are asymmetrically inherited in human blood stem cells and that their inheritance is a coordinated, nonrandom process. Furthermore, multiple additional organelles, including autophagosomes, mitophagosomes, autolysosomes, and recycling endosomes, show preferential asymmetric cosegregation with lysosomes. Importantly, asymmetric lysosomal inheritance predicts future asymmetric daughter cell-cycle length, differentiation, and stem cell marker expression, whereas asymmetric inheritance of active mitochondria correlates with daughter metabolic activity. Hence, human hematopoietic stem cell fates are regulated by asymmetric cell division, with both mechanistic evolutionary conservation and differences to the mouse system.
•Asymmetric inheritance of lysosomes and mitochondria predicts future human blood stem cell daughter behavior and marker expression.•The asymmetric inheritance of multiple organelles is a coordinated process.
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Hematopoietic stem cells (HSCs) maintain blood production. How often mouse HSCs divide and whether each HSC contributes simultaneously, sequentially, or repetitively to hematopoiesis remains to be ...determined. We track division of 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled HSC in vivo. We found that, in steady-state mice, bone marrow cells capable of reconstituting lifelong hematopoiesis are found within both fast-cycling (undergoing five or more divisions in 7 wk) and quiescent (undergoing zero divisions in 12-14 wk) lineage marker-negative c-Kit(+) Sca-1(+) populations. The contribution of each population to hematopoiesis can fluctuate with time, and cells with extensive proliferative history are prone to return to quiescence. Furthermore, injection of the bacterial component lipopolysaccharide increased the proliferation and self-renewal capacity of HSCs. These findings suggest a model in which all HSCs undergo dynamic and demand-adapted entry into and exit out of the cell cycle over time. This may facilitate a similar degree of turnover of the entire HSC pool at the end of life.
Lymphoid tissue plasmacytoid and conventional dendritic cells (DCs) are continuously regenerated from hematopoietic stem cells. The cytokine dependence and biology of plasmacytoid and conventional ...DCs suggest that regeneration might proceed through common DC-restricted developmental intermediates. By selecting for cytokine receptor expression relevant to DC development, we identify here highly cycling Lin(-)c-Kit(int)Flt3(+)M-CSFR(+) cells with a distinct gene-expression profile in mouse bone marrow that, on a clonal level in vitro and as a population both in vitro and in vivo, efficiently generated plasmacytoid and conventional DCs but no other lineages, which increased in number after in vivo injection of the cytokine Flt3 ligand. These clonogenic common DC progenitors thus define a cytokine-regulated DC developmental pathway that ensures the supply of various DC populations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Sinusoidal endothelial cells and mesenchymal CXCL12-abundant reticular cells are principal bone marrow stromal components, which critically modulate haematopoiesis at various levels, including ...haematopoietic stem cell maintenance. These stromal subsets are thought to be scarce and function via highly specific interactions in anatomically confined niches. Yet, knowledge on their abundance, global distribution and spatial associations remains limited. Using three-dimensional quantitative microscopy we show that sinusoidal endothelial and mesenchymal reticular subsets are remarkably more abundant than estimated by conventional flow cytometry. Moreover, both cell types assemble in topologically complex networks, associate to extracellular matrix and pervade marrow tissues. Through spatial statistical methods we challenge previous models and demonstrate that even in the absence of major specific interaction forces, virtually all tissue-resident cells are invariably in physical contact with, or close proximity to, mesenchymal reticular and sinusoidal endothelial cells. We further show that basic structural features of these stromal components are preserved during ageing.
The applicability of
-internal tandem duplications (
-ITD) for assessing measurable residual disease (MRD) in acute myeloid leukemia (AML) in complete remission (CR) has been hampered by ...patient-specific duplications and potential instability of
-ITD during relapse. Here, we comprehensively investigated the impact of next-generation sequencing (NGS)-based
-ITD MRD detection on treatment outcome in a cohort of patients with newly diagnosed AML in relation to established prognostic factors at diagnosis and other MRD measurements, ie, mutant
and multiparameter flow cytometry.
In 161 patients with de novo
-ITD AML, NGS was performed at diagnosis and in CR after intensive remission induction treatment.
-ITD MRD status was correlated with the cumulative incidence of relapse and overall survival (OS).
NGS-based
-ITD MRD was present in 47 of 161 (29%) patients with AML. Presence of
-ITD MRD was associated with increased risk of relapse (4-year cumulative incidence of relapse, 75%
-ITD MRD
33% no
-ITD MRD;
< .001) and inferior OS (4-year OS, 31%
-ITD MRD
57% no
-ITD MRD;
< .001). In multivariate analysis, detection of
-ITD MRD in CR confers independent prognostic significance for relapse (hazard ratio, 3.55;
< .001) and OS (hazard ratio 2.51;
= .002). Strikingly,
-ITD MRD exceeds the prognostic value of most generally accepted clinical and molecular prognostic factors, including the
-ITD allelic ratio at diagnosis and MRD assessment by NGS-based mutant
detection or multiparameter flow cytometry.
NGS-based detection of
-ITD MRD in CR identifies patients with AML with profound risk of relapse and death that outcompetes the significance of most established prognostic factors at diagnosis and during therapy, and furnishes support for
-ITD as a clinically relevant biomarker for dynamic disease risk assessment in AML.
Increased expression of the chemokine CCL2 in tumor cells correlates with enhanced metastasis, poor prognosis, and recruitment of CCR2+Ly6Chi monocytes. However, the mechanisms driving tumor cell ...extravasation through the endothelium remain elusive. Here, we describe CCL2 upregulation in metastatic UICC stage IV colon carcinomas and demonstrate that tumor cell-derived CCL2 activates the CCR2+ endothelium to increase vascular permeability in vivo. CCR2 deficiency prevents colon carcinoma extravasation and metastasis. Of note, CCR2 expression on radio-resistant cells or endothelial CCR2 expression restores extravasation and metastasis in Ccr2−/− mice. Reduction of CCR2 expression on myeloid cells decreases but does not prevent metastasis. CCL2-induced vascular permeability and metastasis is dependent on JAK2-Stat5 and p38MAPK signaling. Our study identifies potential targets for treating CCL2-dependent metastasis.
► Tumor-cell derived CCL2 controls vascular permeability, extravasation, and metastasis ► Endothelial CCR2 expression is necessary and sufficient for extravasation/ metastasis ► Activation of JAK2-Stat5 and p38MAPK signaling via CCR2 induce vascular permeability ► CCL2 expression levels correlate with metastatic potential of UICC IV colon carcinoma
•Increased BM IL-1 levels during aging drive Tet2+/− clonal expansion via increased HSPC proliferation and multilineage differentiation.•Genetic deletion of IL-1R1 abolishes, and pharmacologic ...inhibition of IL-1–IL-1R1 signaling impairs, Tet2+/− clonal expansion during aging.
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Clonal hematopoiesis of indeterminate potential (CHIP), also referred to as aging-related clonal hematopoiesis, is defined as an asymptomatic clonal expansion of mutant mature hematopoietic cells in ≥4% of blood leukocytes. CHIP associates with advanced age and increased risk for hematological malignancy, cardiovascular disease, and all-cause mortality. Loss-of-function somatic mutations in TET2 are frequent drivers of CHIP. However, the contribution of aging-associated cooperating cell-extrinsic drivers, like inflammation, remains underexplored. Using bone marrow (BM) transplantation and newly developed genetic mosaicism (HSC-SCL-Cre-ERT; Tet2+/flox; R26+/tm6CAG-ZsGreen1Hze) mouse models of Tet2+/−driven CHIP, we observed an association between increased Tet2+/− clonal expansion and higher BM levels of the inflammatory cytokine interleukin-1 (IL-1) upon aging. Administration of IL-1 to mice carrying CHIP led to an IL-1 receptor 1 (IL-1R1)–dependent expansion of Tet2+/− hematopoietic stem and progenitor cells (HSPCs) and mature blood cells. This expansion was caused by increased Tet2+/− HSPC cell cycle progression, increased multilineage differentiation, and higher repopulation capacity compared with their wild-type counterparts. In agreement, IL-1α–treated Tet2+/− hematopoietic stem cells showed increased DNA replication and repair transcriptomic signatures and reduced susceptibility to IL-1α–mediated downregulation of self-renewal genes. More important, genetic deletion of IL-1R1 in Tet2+/− HPSCs or pharmacologic inhibition of IL-1 signaling impaired Tet2+/− clonal expansion, establishing the IL-1 pathway as a relevant and therapeutically targetable driver of Tet2+/− CHIP progression during aging.
Clonal hematopoiesis (CH) is a common, age-associated phenomenon where somatic mutations in hematopoietic stem and progenitor cells impart a selective advantage and expansion of mutant progeny in blood. Using a novel irradiation- and transplantation-free murine model of Tet2-mutant CH, Caiado et al demonstrate the importance of age-associated inflammation (“inflammaging”) in clonal outgrowth and define interleukin-1 signaling as a therapeutically targetable driver of clonal expansion.
Systemic bacterial infection induces a hematopoietic response program termed “emergency granulopoiesis” that is characterized by increased de novo bone marrow (BM) neutrophil production. How loss of ...local immune control and bacterial dissemination is sensed and subsequently translated into the switch from steady-state to emergency granulopoiesis is, however, unknown. Using tissue-specific myeloid differentiation primary response gene 88 (Myd88)-deficient mice and in vivo lipopolysaccharide (LPS) administration to model severe bacterial infection, we here show that endothelial cells (ECs) but not hematopoietic cells, hepatocytes, pericytes, or BM stromal cells, are essential cells for this process. Indeed, ECs from multiple tissues including BM express high levels of Tlr4 and Myd88 and are the primary source of granulocyte colony-stimulating factor (G-CSF), the key granulopoietic cytokine, after LPS challenge or infection with Escherichia coli. EC-intrinsic MYD88 signaling and subsequent G-CSF production by ECs is required for myeloid progenitor lineage skewing toward granulocyte-macrophage progenitors, increased colony-forming unit granulocyte activity in BM, and accelerated BM neutrophil generation after LPS stimulation. Thus, ECs catalyze the detection of systemic infection into demand-adapted granulopoiesis.
•ECs express Tlr4 and Myd88 and, after in vivo LPS or E coli stimulation, are the prime sources of G-CSF.•ECs are sensors of systemically spread pathogens and subsequent drivers of BM emergency granulopoiesis.
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