IL-1 Mediates Microbiome-Induced Inflamm-Aging of Hematopoietic Stem Cells
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ABSTRACT: Mature blood cells are maintained throughout life by hematopoietic stem cells (HSC). With aging, both HSC self-renewal as well as multi-lineage differentiation fidelity decline, a process determined by cell-intrinsic and –extrinsic factors. We here studied which aging-associated bone marrow (BM) alterations contribute to this process. Aged specific pathogen free (SPF) WT mice have increased systemic levels of microbial compounds compared to their young counterparts. This associates with increased steady-state IL-1a/b production by multiple BM cell populations. Aging-associated inflammatory transcriptional signatures and functional myeloid-differentiation bias in HSCs were mitigated in aged IL-1R1KO SPF and WT germ-free mice. Moreover, myeloid cells from aged mice produce more IL-1b and aged mice show higher and more durable IL-1a/b increase to lipopolysaccharide (LPS) challenges. Reducing inflammatory burden in aged mice by inhibiting IL-1 signaling or by antibiotic treatment rejuvenate HSCs functions. Collectively we define the microbiome-IL-1-IL1R1 axis as a key driver of HSC aging.
Project description:The bone marrow (BM) niche comprised of BM endothelial cells (BMECs) and LepR+ mesenchymal stromal cells (MSCs), plays a critical role in preserving the fitness of hematopoietic stem cells (HSCs). Aging is associated with defects in the BM niche that impair their ability to support HSC activity. However, mechanisms underlying age-related defects in the BM niche remain poorly understood. In this study, we identify BM niche derived Netrin-1 (NTN1) as a critical regulator of BM niche cell fitness during aging. Conditional deletion of NTN-1 specifically within BM MSCs or BMECs of young mice resulted in premature aging phenotypes within the BM niche including increased vascular leakiness, hypoxia, DNA damage and adiposity. On the other hand, supplementation of aged mice with NTN1 resulted in restoration of these hallmark niche defects and a rejuvenation of HSC activity. Mechanistically, we identify NTN1 as a critical regulator of DNA Damage Response (DDR) within BM niche cells and HSCs. In this experiment, RNA Seq analysis was performed on HSCs derived from young mice (3 month old), PBS treated aged mice (18 month old), and NTN1 treated aged mice (18 month old), to characterize transcriptional alterations within HSCs during aging, and following NTN1 treatment of aged mice.
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: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:The impact of Thbs1 gene deletion on HSC activity during physiological aging is unknown. In this experiment, RNA Seq analysis was performed on BM HSCs derived from aged (18 month-old) Thbs1 knockout mice. HSCs derived from young (3 month-old) and aged (18 month-old) control mice were used as controls for comparison.
Project description:Bone marrow (BM) is normally maintained in an immune-privileged and anti-inflammatory state, kept in check principally by regulatory T cells (Tregs). Thus, it is reasonable to expect that Tregs will help shield hematopoietic stem cells (HSCs) from excessive inflammation and thereby counteract HSC aging. Understanding how BM Tregs are adapted to the aged BM and whether they are endowed with unique functions to modulate HSC aging will identify targets for prevention of HSC aging. To identify the phenotype switching and function variation in BM Tregs with physiological and premature aging, we performed RNA-seq of Tregs from the bone marrow of mice at three months post irradiation (IR) and their age-matched control mice (Ctrl).
Project description:The bone marrow (BM) niche comprised of BM endothelial cells (BMECs) and LepR+ mesenchymal stromal cells (MSCs), plays a critical role in preserving the fitness of hematopoietic stem cells (HSCs). Aging is associated with defects in the BM niche that impair their ability to support HSC activity. However, mechanisms underlying age-related defects in the BM niche remain poorly understood. In this study, we identify BM niche derived Netrin-1 (NTN1) as a critical regulator of BM niche cell fitness during aging. Conditional deletion of NTN-1 specifically within BM MSCs or BMECs of young mice resulted in premature aging phenotypes within the BM niche including increased vascular leakiness, hypoxia, DNA damage and adiposity. On the other hand, supplementation of aged mice with NTN1 resulted in restoration of these hallmark niche defects and a rejuvenation of HSC activity. Mechanistically, we identify NTN1 as a critical regulator of DNA Damage Response (DDR) within BM niche cells and HSCs. In this experiment, RNA Seq analysis was performed on BM MSCs derived from young (3 month old) and aged (18 month old) mice to characterize transcriptional alterations within BM MSCs during aging.
Project description:The bone marrow (BM) niche comprised of BM endothelial cells (BMECs) and LepR+ mesenchymal stromal cells (MSCs), plays a critical role in preserving the fitness of hematopoietic stem cells (HSCs). Aging is associated with defects in the BM niche that impair their ability to support HSC activity. However, mechanisms underlying age-related defects in the BM niche remain poorly understood. In this study, we identify BM niche derived Netrin-1 (NTN1) as a critical regulator of BM niche cell fitness during aging. Conditional deletion of NTN-1 specifically within BM MSCs or BMECs of young mice resulted in premature aging phenotypes within the BM niche including increased vascular leakiness, hypoxia, DNA damage and adiposity. On the other hand, supplementation of aged mice with NTN1 resulted in restoration of these hallmark niche defects and a rejuvenation of HSC activity. Mechanistically, we identify NTN1 as a critical regulator of DNA Damage Response (DDR) within BM niche cells and HSCs. In this experiment, RNA Seq analysis was performed on BMECs derived from young (3 month old) and aged (18 month old) mice to characterize transcriptional alterations within BMECs during aging.
Project description:Long-term hematopoietic stem cells (LT-HSCs) are responsible for lifelong maintenance and regeneration of the blood system. Loss of LT-HSC function is a major contributor to decline in hematopoietic function with aging, leading to increased rate of infection, poor vaccination response, and increased risk of hematologic malignancies. While cellular and molecular hallmarks of LT-HSC aging have been defined1-3, a barrier to achieving the goal of extending healthy hematopoietic function into older age is the lack of understanding of the nature and timing of the initiating events that cause LT-HSC aging. Here we show that hallmarks of LT-HSC aging and decline in hematopoietic function accumulate by middle age in mice, and that the hematopoietic cell-extrinsic bone marrow (BM) microenvironment at middle age is necessary and sufficient to cause LT-HSC aging. Using unbiased transcriptome-based approaches, we identify decreased production of IGF1 by mesenchymal stromal cells (MSC) in the local middle-aged BM microenvironment as a factor causing LT-HSC aging and show that direct stimulation of middle-aged LT-HSCs with IGF1 rescues hallmarks of aging. Together, our study demonstrates that the initiating events causing LT-HSC and hematopoietic aging emerge by middle age and are caused by hematopoietic cell-extrinsic changes in the BM microenvironment. Declining IGF1 in the BM microenvironment at middle age represents a compelling target for intervention using prophylactic therapies to effectively extend healthspan and prevent decline in hematopoietic function during aging.
Project description:Long-term hematopoietic stem cells (LT-HSCs) are responsible for lifelong maintenance and regeneration of the blood system. Loss of LT-HSC function is a major contributor to decline in hematopoietic function with aging, leading to increased rate of infection, poor vaccination response, and increased risk of hematologic malignancies. While cellular and molecular hallmarks of LT-HSC aging have been defined1-3, a barrier to achieving the goal of extending healthy hematopoietic function into older age is the lack of understanding of the nature and timing of the initiating events that cause LT-HSC aging. Here we show that hallmarks of LT-HSC aging and decline in hematopoietic function accumulate by middle age in mice, and that the hematopoietic cell-extrinsic bone marrow (BM) microenvironment at middle age is necessary and sufficient to cause LT-HSC aging. Using unbiased transcriptome-based approaches, we identify decreased production of IGF1 by mesenchymal stromal cells (MSC) in the local middle-aged BM microenvironment as a factor causing LT-HSC aging and show that direct stimulation of middle-aged LT-HSCs with IGF1 rescues hallmarks of aging. Together, our study demonstrates that the initiating events causing LT-HSC and hematopoietic aging emerge by middle age and are caused by hematopoietic cell-extrinsic changes in the BM microenvironment. Declining IGF1 in the BM microenvironment at middle age represents a compelling target for intervention using prophylactic therapies to effectively extend healthspan and prevent decline in hematopoietic function during aging.
Project description:Long-term hematopoietic stem cells (LT-HSCs) are responsible for lifelong maintenance and regeneration of the blood system. Loss of LT-HSC function is a major contributor to decline in hematopoietic function with aging, leading to increased rate of infection, poor vaccination response, and increased risk of hematologic malignancies. While cellular and molecular hallmarks of LT-HSC aging have been defined, a barrier to achieving the goal of extending healthy hematopoietic function into older age is the lack of understanding of the nature and timing of the initiating events that cause LT-HSC aging. Here we show that hallmarks of LT-HSC aging and decline in hematopoietic function accumulate by middle age in mice, and that the hematopoietic cell-extrinsic bone marrow (BM) microenvironment at middle age is necessary and sufficient to cause LT-HSC aging. Using unbiased transcriptome-based approaches, we identify decreased production of IGF1 by mesenchymal stromal cells (MSC) in the local middle-aged BM microenvironment as a factor causing LT-HSC aging and show that direct stimulation of middle-aged LT-HSCs with IGF1 rescues hallmarks of aging. Together, our study demonstrates that the initiating events causing LT-HSC and hematopoietic aging emerge by middle age and are caused by hematopoietic cell-extrinsic changes in the BM microenvironment. Declining IGF1 in the BM microenvironment at middle age represents a compelling target for intervention using prophylactic therapies to effectively extend healthspan and prevent decline in hematopoietic function during aging.