Clonal hematopoiesis driven by mutations of DNMT3A (DNA methyltransferase 3a) is associated with increased incidence of cardiovascular disease and poor prognosis of patients with chronic heart ...failure (HF) and aortic stenosis. Although experimental studies suggest that DNMT3A clonal hematopoiesis-driver mutations may enhance inflammation, specific signatures of inflammatory cells in humans are missing.
To define subsets of immune cells mediating inflammation in humans using single-cell RNA sequencing.
Transcriptomic profiles of peripheral blood mononuclear cells were analyzed in n=6 patients with HF harboring DNMT3A clonal hematopoiesis-driver mutations and n=4 patients with HF and no DNMT3A mutations by single-cell RNA sequencing. Monocytes of patients with HF carrying DNMT3A mutations demonstrated a significantly increased expression of inflammatory genes compared with monocytes derived from patients with HF without DNMT3A mutations. Among the specific upregulated genes were the prototypic inflammatory IL (interleukin)
, the inflammasome
, and the macrophage inflammatory proteins
and
as well as resistin, which augments monocyte-endothelial adhesion. Silencing of DNMT3A in monocytes induced a paracrine proinflammatory activation and increased adhesion to endothelial cells. Furthermore, the classical monocyte subset of DNMT3A mutation carriers showed increased expression of T-cell stimulating immunoglobulin superfamily members
,
,
, as well as the CD2 ligand and cell adhesion molecule
, all of which may be involved in monocyte-T-cell interactions. DNMT3A mutation carriers were further characterized by increased expression of the T-cell alpha receptor constant chain and changes in T helper cell 1, T helper cell 2, T helper cell 17, CD8+ effector, CD4+ memory, and regulatory T-cell-specific signatures.
This study demonstrates that circulating monocytes and T cells of patients with HF harboring clonal hematopoiesis-driver mutations in DNMT3A exhibit a highly inflamed transcriptome, which may contribute to the aggravation of chronic HF.
Abstract
Aims
Clonal haematopoiesis of indeterminate potential (CHIP), defined as the presence of an expanded somatic blood cell clone without other haematological abnormalities, was recently shown ...to increase with age and is associated with coronary artery disease and calcification. The most commonly mutated CHIP genes, DNMT3A and TET2, were shown to regulate inflammatory potential of circulating leucocytes. The incidence of degenerative calcified aortic valve (AV) stenosis increases with age and correlates with chronic inflammation. We assessed the incidence of CHIP and its association with inflammatory blood cell phenotypes in patients with AV stenosis undergoing transfemoral aortic valve implantation (TAVI).
Methods and results
Targeted amplicon sequencing for DNMT3A and TET2 was performed in 279 patients with severe AV stenosis undergoing TAVI. Somatic DNMT3A- or TET2-CHIP-driver mutations with a VAF ≥ 2% were detected in 93 out of 279 patients (33.3%), with an age-dependent increase in the incidence from 25% (55–69 years) to 52.9% (90–100 years). Patients with DNMT3A- or TET2-CHIP-driver mutations did not differ from patients without such mutations in clinical parameters, concomitant atherosclerotic disease, blood cell counts, inflammatory markers, or procedural characteristics. However, patients with DNMT3A- or TET2-CHIP-driver mutations had a profoundly increased medium-term all-cause mortality following successful TAVI. Differential myeloid and T-cell distributions revealed pro-inflammatory T-cell polarization in DNMT3A-mutation carriers and increased pro-inflammatory non-classical monocytes in TET2-mutation carriers.
Conclusion
This is the first study to show that acquired somatic mutations in the most commonly mutated CHIP-driver genes occur frequently in patients with severe degenerative AV stenosis, are associated with increased pro-inflammatory leucocyte subsets, and confer a profound increase in mortality following successful TAVI.
The concise review by Kenneth Walsh and colleagues summarizes the clinical association of clonal hematopoiesis and chronic heart failure, and the mechanistic insights into this unexpected relation of ...mutated blood cells and heart failure progression, which shows great promise to lead into therapeutic applications in the future 1. While the existence of dominant blood cell clones in healthy individuals was described more than 25 years ago 4, only in recent years has the presence of recurrent somatic mutations in the hematopoietic system leading to the expansion of the mutated blood cell clone been widely recognized 5. Nicholas Chavkin et al. have excellently addressed these and other questions in the context of the current clinical and experimental view of the detrimental relationship of blood stem cell mutations and chronic heart failure progression 1.
Dormant hematopoietic stem cells (dHSCs) are atop the hematopoietic hierarchy. The molecular identity of dHSCs and the mechanisms regulating their maintenance or exit from dormancy remain uncertain. ...Here, we use single-cell RNA sequencing (RNA-seq) analysis to show that the transition from dormancy toward cell-cycle entry is a continuous developmental path associated with upregulation of biosynthetic processes rather than a stepwise progression. In addition, low Myc levels and high expression of a retinoic acid program are characteristic for dHSCs. To follow the behavior of dHSCs in situ, a Gprc5c-controlled reporter mouse was established. Treatment with all-trans retinoic acid antagonizes stress-induced activation of dHSCs by restricting protein translation and levels of reactive oxygen species (ROS) and Myc. Mice maintained on a vitamin A-free diet lose HSCs and show a disrupted re-entry into dormancy after exposure to inflammatory stress stimuli. Our results highlight the impact of dietary vitamin A on the regulation of cell-cycle-mediated stem cell plasticity.
Display omitted
Display omitted
•Continuous increase of biosynthesis during transition from dormant to active HSCs•Gprc5c-EGFP reporter mice allow identification and isolation of dormant HSCs•Retinoic acid-vitamin A regulates HSC plasticity during stress-mediated activation•Vitamin A-deficient diet impairs the HSC compartment in mice
Metabolic inputs control the entry and exit of hematopoietic stem cells from dormancy and suggest the potential application of vitamin A in hematopoietic disorders and leukemias.
Abstract
Aims
Somatic mutations of the epigenetic regulators DNMT3A and TET2 causing clonal expansion of haematopoietic cells (clonal haematopoiesis; CH) were shown to be associated with poor ...prognosis in chronic ischaemic heart failure (CHF). The aim of our analysis was to define a threshold of variant allele frequency (VAF) for the prognostic significance of CH in CHF.
Methods and results
We analysed bone marrow and peripheral blood-derived cells from 419 patients with CHF by error-corrected amplicon sequencing. Cut-off VAFs were optimized by maximizing sensitivity plus specificity from a time-dependent receiver operating characteristic (ROC) curve analysis from censored data. 56.2% of patients were carriers of a DNMT3A- (N = 173) or a TET2- (N = 113) mutation with a VAF >0.5%, with 59 patients harbouring mutations in both genes. Survival ROC analyses revealed an optimized cut-off value of 0.73% for TET2- and 1.15% for DNMT3A-CH-driver mutations. Five-year-mortality was 18% in patients without any detected DNMT3A- or TET2 mutation (VAF < 0.5%), 29% with only one DNMT3A- or TET2-CH-driver mutations above the respective cut-off level and 42% in patients harbouring both DNMT3A- and TET2-CH-driver mutations above the respective cut-off levels. In carriers of a DNMT3A mutation with VAF ≥ 1.15%, 5-year mortality was 31%, compared with 18% mortality in those with VAF < 1.15% (P = 0.048). Likewise, in patients with TET2 mutations, 5-year mortality was 32% with VAF ≥ 0.73%, compared with 19% mortality with VAF < 0.73% (P = 0.029).
Conclusion
The present study defines novel threshold levels for clone size caused by acquired somatic mutations in the CH-driver genes DNMT3A and TET2 that are associated with worse outcome in patients with CHF.
Graphical Abstract
•Clonal hematopoiesis (CH) is associated with atherosclerosis, heart failure, and stroke.•Common risk factors prompt CH, cancer, and cardiovascular diseases (CVD).•Inflammation promotes CVD and ...affects tissue regeneration.•The outcome of heart failure and aortic valve stenosis patients with DNMT3A/TET2-CH mutations is poor.•A vicious circuit is induced by CH-mutated myeloid cells on CVDs and hematopoiesis.
Cardiovascular diseases (CVDs) remain the leading cause of death worldwide. Many studies have provided evidence that both genetic and environmental factors induce atherosclerosis, leading thus to cardiovascular complications. Atherosclerosis is an inflammatory disease, and aging is strongly associated with the development of atherosclerosis. Recent experimental evidence suggests that clonal hematopoiesis (CH) is an emerging cardiovascular risk factor that contributes to the development of atherosclerosis and cardiac dysfunction and exacerbates cardiovascular diseases. CH is caused by somatic mutations in recurrent genes in hematopoietic stem cells, leading to the clonal expansion of mutated blood cell clones. Many of the mutated genes are known in the context of myeloid neoplasms. However, only some individuals carrying CH mutations develop hematologic abnormalities. CH is clearly age dependent and is not rare: at least 10%–20% of people >70 years old carry CH. The newly discovered association between myeloid leukemia-driver mutations and the progression of CVDs has raised medical interest. In this review, we summarize the current view on the contribution of CH in different cardiovascular diseases, CVD risk assessment, patient stratification, and the development of novel therapeutic strategies.
Hematopoiesis Rieger, Michael A; Schroeder, Timm
Cold Spring Harbor perspectives in biology,
2012-Dec-01, 2012-12-01, 20121201, Letnik:
4, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Enormous numbers of adult blood cells are constantly regenerated throughout life from hematopoietic stem cells through a series of progenitor stages. Accessibility, robust functional assays, ...well-established prospective isolation, and successful clinical application made hematopoiesis the classical mammalian stem cell system. Most of the basic concepts of stem cell biology have been defined in this system. At the same time, many long-standing disputes in hematopoiesis research illustrate our still limited understanding. Here we discuss the embryonic development and lifelong maintenance of the hematopoietic system, its cellular components, and some of the hypotheses about the molecular mechanisms involved in controlling hematopoietic cell fates.
Hematopoietic Cytokines Can Instruct Lineage Choice Rieger, Michael A; Hoppe, Philipp S; Smejkal, Benjamin M ...
Science (American Association for the Advancement of Science),
07/2009, Letnik:
325, Številka:
5937
Journal Article
Recenzirano
The constant regeneration of the blood system during hematopoiesis requires tightly controlled lineage decisions of hematopoietic progenitor cells (HPCs). Because of technical limitations, ...differentiation of individual HPCs could not previously be analyzed continuously. It was therefore disputed whether cell-extrinsic cytokines can instruct HPC lineage choice or only allow survival of cells that are already lineage-restricted. Here, we used bioimaging approaches that allow the continuous long-term observation of individual differentiating mouse HPCs. We demonstrate that the physiological cytokines, macrophage colony-stimulating factor and granulocyte colony-stimulating factor, can instruct hematopoietic lineage choice.
RATIONALE:Vascularization is critical to maintain organ function. Although many molecular pathways were shown to control vessel growth, the genuine process of capillary formation under different ...conditions is unclear.
OBJECTIVE:Here, we elucidated whether clonal expansion contributes to vessel growth by using Confetti mice for genetic tracing of clonally expanding endothelial cells (ECs).
METHODS AND RESULTS:In postnatal retina angiogenesis, we predominantly observed random distribution of fluorescence labeled ECs indicative of random integration or cell mixing. However, in models of pathophysiological angiogenesis (retinopathy of prematurity), as well as ischemia-induced angiogenesis in limbs and hearts, clonally expanded ECs were significantly more abundant (≤69%). Inhibition of VEGFR2 (vascular endothelial growth factor receptor 2) reduced clonal expansion after ischemia. To determine the mechanism underlying clonal expansion in vivo, we assessed gene expression specifically in clonally expanded ECs selected by laser capture microscopy. Clonally expanded ECs showed an enrichment of genes involved in endothelial-to-mesenchymal transition. Moreover, hypoxia-induced clonal expansion and endothelial-to-mesenchymal transition in ECs in vitro suggesting that hypoxia-enhanced endothelial-to-mesenchymal transition might contribute to vessel growth under ischemia.
CONCLUSIONS:Our data suggest that neovascularization after ischemia is partially mediated by clonal expansion of ECs. Identification of the pathways that control clonal expansion may provide novel tools to augment therapeutic neovascularization or treat pathological angiogenesis.
Haematopoietic stem cells (HSCs) are responsible for the lifelong production of blood cells. The accumulation of DNA damage in HSCs is a hallmark of ageing and is probably a major contributing factor ...in age-related tissue degeneration and malignant transformation. A number of accelerated ageing syndromes are associated with defective DNA repair and genomic instability, including the most common inherited bone marrow failure syndrome, Fanconi anaemia. However, the physiological source of DNA damage in HSCs from both normal and diseased individuals remains unclear. Here we show in mice that DNA damage is a direct consequence of inducing HSCs to exit their homeostatic quiescent state in response to conditions that model physiological stress, such as infection or chronic blood loss. Repeated activation of HSCs out of their dormant state provoked the attrition of normal HSCs and, in the case of mice with a non-functional Fanconi anaemia DNA repair pathway, led to a complete collapse of the haematopoietic system, which phenocopied the highly penetrant bone marrow failure seen in Fanconi anaemia patients. Our findings establish a novel link between physiological stress and DNA damage in normal HSCs and provide a mechanistic explanation for the universal accumulation of DNA damage in HSCs during ageing and the accelerated failure of the haematopoietic system in Fanconi anaemia patients.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
