Project description:The decline of hematopoietic stem cell (HSC) function upon aging contributes to senescent immune remodeling and to leukemia pathogenesis. Aged HSCs show epigenetic alterations affecting DNA methylation, histone modifications, and show a reduction in the polar distribution of histone 4 lysine 16 acetylation (H4K16ac). Here, we determined the deposition patterns of H4K16ac in young, aged and re-juvenated HSCs using ChIP-seq.
Project description:Hematopoietic aging is associated with decreased hematopoietic stem cell (HSC) self-renewal capacity and increased risk for myelodysplasia and leukemia. Deficient DNA repair contributes to the decline in HSC self-renewal capacity during aging and it remains unclear whether extrinsic signals can rejuvenate aged HSCs. Here, we demonstrate that augmentation of non-homologous end-joining (NHEJ) DNA repair in aged HSCs via treatment with epidermal growth factor (EGF) rejuvenates HSC function. Seven day culture of BM CD34-ckit+sca-1+lin- (34-KSL) HSCs from aged C57BL/6 mice with EGF suppressed myeloid skewing and increased production of multipotent CFU-granulocyte, erythroid, monocyte and megakaryocyte (CFU-GEMM) colonies. Aged, EGF-treated HSCs displayed increased donor multilineage engraftment in primary competitively transplanted mice and in secondary mice compared to mice transplanted with aged, control HSCs. Donor cell engraftment within the bone marrow (BM) KSL and SLAM+KSL HSC population was > 2-fold increased in mice transplanted with aged, EGF-treated HSCs. Systemic administration of EGF to aged mice for 6 weeks also increased long term – HSC self-renewal capacity as measured by increased donor bone marrow (BM) competitive repopulation in primary and secondary transplanted mice. Conversely, deletion of EGFR in Scl/Tal1+ hematopoietic cells was associated with increased myeloid skewing and depletion of LT-HSCs in middle aged mice. Mechanistically, EGF treatment decreased DNA damage in aged HSCs through activation of DNA PK-cs, Artemis and NHEJ repair. Inhibition of DNA PK-cs blocked EGF-mediated restoration of multipotent differentiation and suppression of myeloid skewing in aged HSCs, suggesting that the restoration of hematopoietic potential in aged HSCs is dependent on EGF-mediated activation of DNA PK-cs. EGF treatment also converted the transcriptome of aged HSCs from enrichment for genes involved in cell death and survival to genes involved in HSC generation and identity. These data suggest that extrinsic activation of EGFR signaling can restore key functional capacities in aged HSCs.
Project description:With ageing, intrinsic hematopoietic stem cell (HSC) activity decreases, resulting in impaired tissue homeostasis, reduced engraftment following transplantation and increased susceptibility to diseases. However, whether ageing affects also the HSC niche impairing the capacity to support HSC function is still largely unknown. Here, by using in-vivo long-term label retention assays we demonstrate that aged labelling retaining (LR) HSCs, which are in the old mice the most quiescent HSC subpopulation with the highest regenerative capacity and cellular polarity, reside predominantly in perisinusoidal niches. Furthermore, we demonstrate that sinusoidal niches and perisinusoidal Nes-GFPlow cells are uniquely preserved in shape, morphology and number upon ageing. Finally, we show that myeloablative chemotherapy can selectively disrupt aged sinusoidal niches, which is linked to hematopoietic failure and decreased survival of aged mice. Overall, our data characterize for the first time the functional alterations of the aged HSC niche and unveil that perisinusoidal niches are uniquely preserved and protect HSCs from ageing.
Project description:Hematopoietic stem cells (HSCs) exhibit considerable cell-intrinsic changes with age. Here, we performed an integrated analysis of transcriptome and chromatin accessibility of aged HSCs and downstream progenitors. Alterations in chromatin accessibility preferentially took place in HSCs with aging, which gradually resolved with differentiation. Differentially open accessible regions (open DARs) in aged HSCs showed enrichment of binding motifs of the STAT, ATF, and CNC family transcription factors that are activated in response to external stresses, and most of them comprised active, primed , and inactive enhancers. Genes linked to open DARs showed significantly higher levels of basal expression and their expression reached significantly higher peaks after cytokine stimulation in aged HSCs than in young HSCs, suggesting that open DARs contribute to augmented transcriptional responses under stress conditions. These results indicate that the ongoing and/or history of exposure to external stresses is epigenetically inscribed in HSCs to augment their responses to external stimuli.
Project description:Hematopoietic stem cells (HSCs) exhibit considerable cell-intrinsic changes with age. Epigenetic alterations are one of the hallmarks of HSC aging, and profiling of DNA methylation and histone modifications has provided potential mechanisms that contribute to HSC aging. Chromatin accessibility reflects a comprehensive transcriptional network operating in cells; however, it has not yet been investigated in HSC aging. Here we performed an integrated analysis of aged HSCs on transcriptome, chromatin accessibilities, and histone modifications. Alterations in chromatin accessibility preferentially took place in HSCs with aging, the cells at the top of hematopoietic hierarchy, suggesting that the age-associated alterations in chromatin accessibility are memorized in HSCs and are inherited to downstream progenitor cells. However, most genes with differentially accessible regions (DARs) were not actively transcribed and kept poised for activation in aged HSCs. Motifs of ATF/CREB, STAT, and CNC family transcription factors were significantly enriched at DARs in aged HSCs. These transcription factors are activated in response to external stresses such as cytokine and inflammation signals and oxidative stresses, suggesting that the long-term exposure to such stress signals have changed chromatin accessibility in HSCs to augment responses by such trained HSCs to subsequent stimuli. In contrast, aged HSC-specific gene expression occurred mainly at gene loci with poised accessible regions but not DARs without accompanying drastic chromatin reorganization, suggesting that altered cell-extrinsic stimuli or signals from aged niche largely account for this process. Our findings provide key epigenetic molecular insights into HSC aging and serve as a reference for future analysis.
Project description:Phenotypic and functional changes seen in the aged adaptive immune system are primarily driven by aging of hematopoietic stem cells (HSCs), pharmacological rejuvenated aged HSCs were able to reconstituted a youthful immune system
Project description:Aging of the hematopoietic system is associated with cytopenia and increased risk of hematological malignancies. To investigate cell-intrinsic factors underlying aging of hematopoiesis, we profiled transcriptome, chromatin accessibility, histone modifications in young and aged Hematopoietic stem cells (HSCs) and progenitors. Various differentially expressed genes were detected in each fraction. Changes of transcriptome were more drastic in progenitors than in HSCs. In contrast, aberrant chromatin accessible regions were accumulated particularly in aged HSCs without affecting steady-state transcriptions of nearest genes. These regions were enriched for motif of STAT3, STAT5, c-Jun-CRE, NF-E2, NRF2. We also found H3K27me3 marked genes and bivalent genes were substantially decreased in aged HSCs, some of which became active state and some of which became more repressive state with increased DNA methylation. Our data indicates that integrated analysis of epigenome and transcriptome provides more profound insights into aging of hematopoietic systems.
Project description:During X chromosome inactivation (XCI), the inactive X chromosome (Xi) is recruited to the nuclear lamina at the periphery of the nucleus. Beside X chromosome (X chr) reactivation resulting in a highly penetrant aging-like hematopoietic malignancy, little is known about XCI in aged hematopoietic stem cells (HSCs) . Here, we demonstrate that LaminA/C defines a distinct repressive nuclear compartment for XCI in young HSCs, and its reduction in aged HSCs correlates with an impairment in the overall control of XCI. Integrated omics analyses reveal higher variation in gene expression, global hypomethylation and significantly increased chromatin accessibility on the X chr in aged HSCs. In summary, our data support the role of LaminA/C in the establishment of a special repressive compartment for XCI in HSCs, which is impaired upon aging.
Project description:Purpose: Compare the transcriptome of hematopoietic stem cells (HSCs) that were aged in old and young niches Methods: barcoded GFP+ HSCs were FACS-sorted from a) three recipient mice 15 months post transplantation, and b) six serial transplantation recipient mice 5 months after the 8th transplantation, then subjected to processed using the Chromium Single-cell 3′ v2 Library Kit (10× Genomics, Pleasanton, CA) following the manufacturer’s instructions Results: we obtained transcriptomes of about 12k HSCs aged in young niche, and about 10k HSCs aged in old niche, with the average sequencing depth at close to 50k reads per cell Conclusions: we identified striking differences in gene expression profiles 1) between HSCs aged in young niches from mice with early aging and from mice with delayed aging, and 2) between HSCs aged in old niches and young niches when mice exhibited hematopoietic aging phenotype
Project description:MTD project_description Inflammation and decreased stem cell function characterize organism aging, yet the relationship between these factors remains incompletely understood. This study shows that aged hematopoietic stem and progenitor cells exhibit increased ground-stage NF-κB activity, which enhances their responsiveness to undergo differentiation and loss of self-renewal in response to inflammation. The study identifies Rad21/cohesin as a critical mediator of NF-κB signals, by increasing chromatin accessibility of inter-/intra-genic and enhancer regions. Rad21/NF-κB are required for normal differentiation, but limit self-renewal of hematopoietic stem cells (HSCs) during aging and inflammation in an NF-κB dependent manner. HSCs from aged mice fail to downregulate Rad21/cohesin and inflammation/differentiation inducing signals in the resolution phase after acute inflammation. and The inhibition of cohesin/NF-κB is sufficient to revert the hypersensitivity of aged HSPCs to inflammation-induced differentiation. During aging, myeloid-biased HSCs with disrupted and naturally occurring reduced expression of Rad21/cohesin are increasingly selected over lymphoid-biased HSCs. Together, Rad21/cohesin mediated NF-κB signaling limits HSPC function during aging and selects for cohesin deficient HSCs with myeloid skewed differentiation.