Project description:Hematopoietic aging is defined by a loss of regenerative capacity and skewed differentiation from hematopoietic stem cells (HSC) leading to dysfunctional blood production. Signals from the bone marrow (BM) microenvironment dynamically tailor hematopoiesis, but the effect of aging on the niche and the contribution of the aging niche to blood aging still remains unclear. Here, we show the development of an inflammatory milieu in the aged marrow cavity, which drives both niche and hematopoietic system remodeling. We find decreased numbers and functionality of osteogenic endosteal mesenchymal stromal cells (MSC), expansion of pro-inflammatory perisinusoidal MSCs, and deterioration of the central marrow sinusoidal endothelium, which together create a self-reinforcing inflamed BM milieu. Single cell molecular mapping of old niche cells further confirms disruption of cell identities and enrichment of inflammatory response genes. Inflammation, in turn, drives chronic activation of emergency myelopoiesis pathways in old HSCs and multipotent progenitors, which promotes myeloid differentiation at the expense of lymphoid and erythroid commitment, and hinders hematopoietic regeneration. Remarkably, both defective hematopoietic regeneration, niche deterioration and HSC aging can be improved by blocking inflammatory IL-1 signaling. Our results indicate that targeting the pro-inflammatory niche milieu can be instrumental in restoring blood production 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 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: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: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 BM MSCs and BMECs following conditional deletion of NTN1 within BMECs or MSCs to characterize transcriptional alterations within BM niche cells resulting from a deficiency of niche derived NTN1.
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 and BMECs following conditional deletion of NTN1 within BMECs or MSCs to characterize transcriptional alterations within BM niche cells resulting from a deficiency of niche derived NTN1.
Project description:Tissue homeostasis and regeneration require activation and subsequent lineage commitment of tissue-resident stem cells (SCs). These state changes are controlled by epigenetic barriers. Using hair follicle stem cells (HFSCs) as paradigm, we studied how aging impacts the chromatin landscape and function of mammalian SCs. Analyses of genome-wide chromatin accessibility revealed that aged HFSCs displayed widespread reduction of chromatin accessibility specifically at key SC self-renewal and differentiation genes that were characterized by bivalent promoters carrying both activating and repressive chromatin marks. Consistently, aged HFSCs showed reduced self-renewing capacity and attenuated ability to activate expression of these bivalent genes upon regeneration. These functional defects were niche-dependent as transplantation of aged HFSCs into young recipients or into ex vivo niches restored SC functions and transcription of poised genes. Mechanistically, aged HFSC niche displayed wide-spread alterations in extracellular matrix composition and mechanics, resulting in compressive forces on SCs and subsequent transcriptional repression, leading to loss of bivalent promoters. Tuning tissue mechanics both in vivo and in vitro recapitulated age-related SC changes, implicating niche mechanics as a central regulator of genome organization and function leading to age-dependent SC exhaustion.
Project description:Age-induced decline in osteogenic potential of bone marrow mesenchymal stem cells (BMSCs) potentiates osteoporosis and increases risk for bone fractures. Despite epidemiology studies reporting concurrent development of vascular- and bone diseases in the elderly, the underlying mechanisms for the vascular-bone cross-talk in aging are largely unknown. In this study, we show that accelerated endothelial aging deteriorates bone tissue through paracrine repression of Wnt-driven-axis in BMSCs. Here, we utilize physiologically aged mice in conjunction with our transgenic endothelial progeria mouse model (Hutchinson-Gilford progeria syndrome; HGPS) that displays hallmarks of an aged bone marrow vascular niche. We find bone defects associated with diminished BMSC osteogenic differentiation that implicate the existence of angiocrine factors with long-term inhibitory effects. microRNA-transcriptomics of HGPS-patient plasma combined with aged-vascular niche analyses in progeria mice reveal abundant secretion of Wnt-repressive microRNA-31-5p. Moreover, we show that inhibition of microRNA-31-5p as well as selective Wnt-activator CHIR99021 boost the osteogenic potential of BMSCs through de-repression and activation of the Wnt-signalling, respectively. Our results demonstrate that the vascular niche significantly contributes to osteogenesis defects in aging and pave ground for microRNA-based therapies of bone loss in elderly.
Project description:During aging, the regenerative capacity of skeletal muscle decreases due to intrinsic changes in muscle stem cells (MuSCs) and alterations in their niche. Here, we used quantitative mass spectrometry to characterize intrinsic changes in the MuSC proteome and remodeling of the MuSC niche during aging. We generated a network connecting age-affected ligands located in the niche and cell surface receptors on MuSCs. Thereby, we revealed signaling via Integrins, Lrp1, Egfr and Cd44 as the major cell communication axes perturbed through aging. We investigated the effect of Smoc2, a secreted protein that accumulates with aging, originating from fibro-adipogenic progenitors. Increased levels of Smoc2 contribute to the aberrant Itgb1/MAPK signaling observed during aging, thereby causing impaired MuSC functionality and muscle regeneration. By connecting changes in the proteome of MuSCs to alterations of their niche, our work will enable a better understanding of how MuSCs are affected during aging.