An Epigenetic Component of Hematopoietic Stem Cell Aging Amenable to Reprogramming Into a Young State
ABSTRACT: Aging of hematopoietic stem cells (HSCs) leads to several functional changes, including alterations affecting self-renewal and differentiation. While it is well established that many of the age-induced changes are intrinsic to HSCs, less is known about the stability of this state. Here, we entertained the hypothesis that HSC aging is driven by the acquisition of permanent genetic mutations. To examine this issue at a functional level in vivo, we applied induced pluripotent stem (iPS) cell reprogramming of aged hematopoietic progenitors and allowed the resulting aged-derived iPS cells to reform hematopoiesis via blastocyst complementation. Next, we functionally characterized iPS-derived HSCs in primary chimeras and following the transplantation of 're-differentiated' HSCs into new hosts; the gold standard to assess HSC function. Our data demonstrate remarkably similar functional properties of iPS-derived and endogenous blastocyst-derived HSCs, despite the extensive chronological and proliferative age of the former. Our results therefore favor a model in which an underlying, but reversible, epigenetic component is a hallmark of HSC aging rather than being driven by an increased DNA mutation burden. Hematopoietic stem cells (HSC) have been sorted out from young and aged steady-state mice, and from recipients transplanted with young and aged bone marrow. Generated iPS and commercially available ES cells were also sorted and analyzed.
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. Overall design: Examination of histone modifications in young, aged and aged/re-juvenated HSCs
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.
Project description:The decline of hematopoietic stem cell (HSC) function upon aging contributes to the senescent immune remodeling and to leukemia pathogenesis. Aged HSCs show changes in their epigenome, like alterations in the global and local DNA/histone methylation and histone acetylation landscape. Previously, we showed a correlation between high Cdc42 activity and the loss of intra-nuclear epigenetic polarity (epipolarity), as indicated by the specific location of histone H4 lysine 16 acetylation (H4K16ac). Here, we show that not all histone modifications display a polar localization and that loss of H4K16ac amount and epipolarity is specific to aged HSCs. Increased levels of H4K16ac are insufficient to restore polarity in aged HSCs and for the restoration of HSC function. Changes in H4K16ac upon aging and rejuvenation of HSCs are correlated to a shift of chromosome 11 architecture and nuclear volume and shape. Surprisingly, by taking advantage of knock-out mouse models we demonstrate that increased Cdc42 activity levels correlate with the repression of LaminA/C expression, which control chromosome 11 distribution, H4K16ac polarity and the nuclear volume and shape of aged HSCs. These chromatin and epigenetic architecture changes are targeted by altering the activity of the small RhoGTPase Cdc42, that regulates LaminA/C. Collectively, our data show that chromatin architecture changes in stem cells are reversible by changing levels of Cdc42 activity, revealing an unanticipated way to pharmacologically target LaminA/C expression and revert alterations of the epigenetic architecture in aged HSCs. Overall design: HSC (>= 200 cells) were first sorted from Young (2-4-month-old) and aged (20-26-month-old; ± CASIN) C57BL/6 mice (>= 3 individuals per experimental arm) and dropped into lysis buffer for subsequent RNA-seq library preparation.
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 Overall design: We employed RNA-seq to assess similarities/differences between naive CD4+ T cells and CD19+ B cells isolated from RAG1-/- recipients transplanted with either young, old or old rejuvenated (CASIN treated) HSCs
Project description:Loss of immune function and an increased incidence of myeloid leukemia are two of the most clinically significant consequences of aging of the hematopoietic system. To better understand the mechanisms underlying hematopoietic aging, we evaluated the cell intrinsic functional and molecular properties of highly purified long-term hematopoietic stem cells (LT-HSCs) from young and old mice. We found that LT-HSC aging was accompanied by cell autonomous changes, including increased stem cell self-renewal, differential capacity to generate committed myeloid and lymphoid progenitors, and diminished lymphoid potential. Expression profiling revealed that LT-HSC aging was accompanied by the systemic down-regulation of genes mediating lymphoid specification and function and up-regulation of genes involved in specifying myeloid fate and function. Moreover, LT-HSCs from old mice expressed elevated levels of many genes involved in leukemic transformation. These data support a model in which age-dependent alterations in gene expression at the stem cell level presage downstream developmental potential and thereby contribute to age-dependent immune decline, and perhaps also to the increased incidence of leukemia in the elderly.
Project description:In the human hematopoietic system, aging is associated with decreased bone marrow cellularity, decreased adaptive immune system function, and increased incidence of anemia and other hematological disorders and malignancies. Recent studies in mice suggest that changes within the hematopoietic stem cell (HSC) population during aging contribute significantly to the manifestation of these age-associated hematopoietic pathologies. While the mouse HSC population has been shown to change both quantitatively and functionally with age, changes in the human HSC and progenitor cell populations during aging have not yet been characterized. Gene expression profiling revealed that aged human HSC transcriptionally up-regulate genes associated with cell cycle, myeloid lineage specification, and myeloid malignancies. These age-associated alterations in the frequency, function, and gene expression profile of human HSC are significantly similar to those changes observed in mouse HSC, suggesting that hematopoietic aging is an evolutionarily conserved process. In order to elucidate the properties of an aged human hematopoietic system that may predispose to age-associated hematopoietic dysfunction, we evaluated HSC and other hematopoietic progenitor populations from healthy, hematologically normal young and elderly human bone marrow samples. We found that aged human HSC increase in frequency, are less quiescent, and exhibit myeloid-biased differentiation potential compared to young HSC.
Project description:Aging of hematopoietic stem cells (HSCs) is associated with the decline of their regenerative capacity, and multi-lineage differentiation potential, contributing to development of blood disorders. The bone marrow microenvironment was recently suggested to influence HSC aging, however the underlying mechanisms remain largely unknown. Here, we show that HSC aging critically depends on bone marrow innervation by the sympathetic nervous system (SNS), as premature loss of SNS nerves or adrenoreceptor b3 (ADRb3) signaling in the microenvironment accelerated the appearance of HSC aging phenotypes reminiscent of physiological aging. Strikingly, supplementation of ADRb3 sympathomimetics to old mice significantly rejuvenated in vivo function of old HSCs, suggesting that the preservation or restitution of SNS innervation during aging may hold the potential for novel HSC rejuvenation strategies. Overall design: mRNA profiles of sorted bone marrow hematopoietic stem cells were generated from saline treated young and old and BRL37344 treated old mice in triplicates by Illumina NextSeq500 sequencing
Project description:Loss of immune function and an increased incidence of myeloid leukemia are two of the most clinically significant consequences of aging of the hematopoietic system. To better understand the mechanisms underlying hematopoietic aging, we evaluated the cell intrinsic functional and molecular properties of highly purified long-term hematopoietic stem cells (LT-HSCs) from young and old mice. We found that LT-HSC aging was accompanied by cell autonomous changes, including increased stem cell self-renewal, differential capacity to generate committed myeloid and lymphoid progenitors, and diminished lymphoid potential. Expression profiling revealed that LT-HSC aging was accompanied by the systemic down-regulation of genes mediating lymphoid specification and function and up-regulation of genes involved in specifying myeloid fate and function. Moreover, LT-HSCs from old mice expressed elevated levels of many genes involved in leukemic transformation. These data support a model in which age-dependent alterations in gene expression at the stem cell level presage downstream developmental potential and thereby contribute to age-dependent immune decline, and perhaps also to the increased incidence of leukemia in the elderly. 3 old mice and 5 young mice were assayed
Project description:To uphold appropriate homeostasis of short-lived blood cells, immature blood cells need to proliferate vigorously. Here, using a conditional H2B-mCherry labeling mouse-model, we characterize hematopoietic stem cell (HSC) and progenitor proliferation dynamics in steady state, upon physiological aging and following several types of induced stress. Following transplantation, HSCs shifted towards higher degrees of proliferation that was sustained long-term. HSCs were, by contrast, poorly recruited into proliferation following cytokine-induced mobilization and after acute depletions of selected blood cell lineages. Using indexed single cell sorting coupled to multiplex gene expression analyses, proliferation history separated candidate HSCs into units with distinct molecular and functional attributes. Our data thereby highlight that HSC proliferation following transplantation is fundamentally different not only from native hematopoiesis but also from other stress contexts, and demonstrate the power of divisional history as a functional criterion to resolve HSC heterogeneity. Overall design: qPCR gene expression profiling of mouse hematopoietic stem cells (HSCs). Four 96-well plates with pre-amplified single HSC bone marrow cell cDNA (with no template controls) were loaded on to a 96.96 Dynamic Array Chip for Gene Expression. Samples Ids follow where 2w or 5w denotes weeks chase before HSC isolation, and P<X>denoted the plate. No cell was sorted into 2 wells on each plate were = No template controls.
Project description:Hematopoietic stem and progenitor cells are a rare, self-renewing bone marrow resident population capable of giving rise to all circulating hematopoietic cells. They can be used therapuetically for reconstituting defective or ablated hematopoietic systems following chemotherapy, and for inducing tolerance toward allografts of the same haplotype as the HSC donor. There are several sources for HSCs, such as the adult bone marrow, or umblical cord blood, which is more replete with such HSCs. However, HSCs obtained from such sources may be immunogenic, especially if isolated from adult bone marrow. To overcome this issue, our lab has establsihed human induced pluripotent stem cell-derived HPCs with the hope of creating a nonimmunogenic, readily available and unlimited source of HSCs to use for therapy. The goal of this study was to compare the gene expression profiles of naturally found HSCs (UCB-CD34+ HSCs) and HPCs differentiated from 4 different human iPS cell lines (iPS-HPCs), so as to determine the variation between the four iPS-HPCs and whether there were any differences between these HPCs and naturally found HSCs. We utilized 4 iPS cells for this study (detailed descriptions are provided below). iPS cells were differentiated into hematopoietic progenitor cells by coculture on OP9 stromal cells, followed by enrichment of CD34+ cells through immunomagnetic bead separation. The UCB-CD34+ cells were isolated from frozen cord samples through immunomagnetic bead separation. Total RNA was isolated and human gene Affymetrix ST 1.0 arrays performed at the University of Iowa DNA core facility. Data was analyzed, normalized and plotted on BRB Array Tools.