Muscle-secreted G-CSF as a metabolic niche factor ameliorates loss of muscle stem cell in aged mice (RNA-seq)
Ontology highlight
ABSTRACT: Function and number of muscle stem cells (satellite cells, SCs) declines with muscle aging. Although SCs are heterogeneous and different subpopulations have been identified, it remains unknown if a specific subpopulation of muscle SCs selectively decreases during aging. Here, we find Pax7Hi cells are dramatically reduced in aged mice and this aged-dependent loss of Pax7Hi cells is metabolically mediated by myofiber-secreted granulocyte-colony stimulating factor G-CSF as the Pax7Hi SCs are replenished by exercise-induced G-CSF in aged mice. Mechanistically, we show that transcription of G-CSF (Csf3) gene in myofibers is regulated by MyoD in a metabolism-dependent manner and the myofibers-secreted G-CSF acts as a metabolic niche factor required for establishing and maintaining the Pax7Hi SC subpopulation in adult and physiological aged mice by promoting the asymmetric division of Pax7Hi and Pax7Mi SCs. Together, our findings uncover a metabolic niche role of muscle metabolism in regulating Pax7 SC heterogeneity in mice.
Project description:Function and number of muscle stem cells (satellite cells, SCs) declines with muscle aging. Although SCs are heterogeneous and different subpopulations have been identified, it remains unknown if a specific subpopulation of muscle SCs selectively decreases during aging. Here, we find Pax7Hi cells are dramatically reduced in aged mice and this aged-dependent loss of Pax7Hi cells is metabolically mediated by myofiber-secreted granulocyte-colony stimulating factor G-CSF as the Pax7Hi SCs are replenished by exercise-induced G-CSF in aged mice. Mechanistically, we show that transcription of G-CSF (Csf3) gene in myofibers is regulated by MyoD in a metabolism-dependent manner and the myofibers-secreted G-CSF acts as a metabolic niche factor required for establishing and maintaining the Pax7Hi SC subpopulation in adult and physiological aged mice by promoting the asymmetric division of Pax7Hi and Pax7Mi SCs. Together, our findings uncover a metabolic niche role of muscle metabolism in regulating Pax7 SC heterogeneity in mice.
Project description:Function and number of muscle stem cells (satellite cells, SCs) declines with muscle aging. Although SCs are heterogeneous and different subpopulations have been identified, it remains unknown if a specific subpopulation of muscle SCs selectively decreases during aging. Here, we find Pax7Hi cells are dramatically reduced in aged mice and this aged-dependent loss of Pax7Hi cells is metabolically mediated by myofiber-secreted granulocyte-colony stimulating factor G-CSF as the Pax7Hi SCs are replenished by exercise-induced G-CSF in aged mice. Mechanistically, we show that transcription of G-CSF (Csf3) gene in myofibers is regulated by MyoD in a metabolism-dependent manner and the myofibers-secreted G-CSF acts as a metabolic niche factor required for establishing and maintaining the Pax7Hi SC subpopulation in adult and physiological aged mice by promoting the asymmetric division of Pax7Hi and Pax7Mi SCs. Together, our findings uncover a metabolic niche role of muscle metabolism in regulating Pax7 SC heterogeneity in mice.
Project description:Skeletal muscle stem cells, or satellite cells (SCs), are essential to regenerate and maintain muscle. Quiescent SCs reside in an asymmetric niche between the basal lamina and myofiber membrane. To repair muscle, SCs activate, proliferate, and differentiate, fusing to repair myofibers or reacquiring quiescence to replenish the SC niche. Little is known about when SCs reacquire quiescence during regeneration or the cellular processes that direct SC fate decisions and progression through myogenesis. Single cell sequencing of myogenic cells in regenerating muscle identifies SCs reacquiring quiescence and reveals that non-cell autonomous signaling networks influence SC fate decisions during regeneration. Single cell RNA-sequencing of regenerating skeletal muscle reveals that RBP expression, including numerous neuromuscular disease-associated RBPs, is temporally regulated in skeletal muscle stem cells and correlates to stages of myogenic differentiation. By combining machine learning with RBP engagement scoring, we discover that the neuromuscular disease associated RBP Hnrnpa2b1 is a differentiation-specifying regulator of myogenesis controlling myogenic cell fate transitions during terminal differentiation.
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:Satellite cells (SCs) are adult muscle stem cells residing in a specialised niche that regulates SC homeostasis. How niche-generated signals integrate to regulate gene expression in SC-derived myoblasts, is poorly understood. We undertook an unbiased approach to study the effect of the SC niche on SC-derived myoblast transcriptional regulation and identified the tumour suppressor p53 as a key player in the regulation of myoblast quiescence. After activation and proliferation, a subpopulation of myoblasts cultured in the presence of the niche upregulates p53 and fails to differentiate. When SC self-renewal is modelled ex vivo in a reserve cell assay, myoblasts treated with Nutlin-3, which increases p53 levels in the cell, fail to differentiate and instead become quiescent. Since both these effects of Nutlin-3 are rescued by siRNA-mediated p53 knockdown we conclude that a tight control of p53 levels in myoblasts regulate the balance between differentiation and return to quiescence.
Project description:Adult stem cells (SCs) are essential for tissue maintenance and regeneration yet are susceptible to SC senescence during aging. Here we demonstrate the importance of cellular NAD+ level and its impact on mitochondrial activity as a pivotal switch to modulate muscle stem cell (MuSC) senescence. Importantly, the induction of the mitochondrial unfolded protein response (UPRmt) and of prohibitin proteins, subsequent to increasing cellular NAD+ with the precursor nicotinamide riboside (NR), rejuvenates MuSCs in aged mice. NR also prevents MuSCs senescence in Mdx mice, a mouse model of muscular dystrophy. Extending these observations to other SC pools and on the organism as a whole, we demonstrate that NR delays neural stem cell (NSC) and melanocyte stem cell (McSC) senescence, while also increasing mouse lifespan. Strategies that conserve cellular NAD+ could therefore be utilized to reprogram dysfunctional SCs in aging and disease to improve lifespan in mammals
Project description:Adult skeletal muscle stem cells, also known satellite cells (SCs), are quiescent and activate in response to injury. However, the activation mechanisms of quiescent SCs (QSCs) remain largely unknown. Here, we investigated the metabolic regulation of SC activation by identifying regulatory metabolites that promote SC activation. Using targeted metabolomics, we found that spermidine acts as a regulatory metabolite to promote SC activation and muscle regeneration in mice. Mechanistically, spermidine activates SCs via generating hypusinated eIF5A. Using SC-specific eIF5A-knockout (KO) and Myod-KO mice, we further found that eIF5A is required for spermidine-mediated SC activation by controlling MyoD translation. More significantly, depletion of eIF5A in SCs results in impaired muscle regeneration in mice. Together, the findings of our study define a novel mechanism that is essential for SC activation and acts via spermidine-eIF5A-mediated MyoD translation. Our findings suggest that the spermidine-eIF5A axis represents a promising pharmacological target in efforts to activate endogenous SCs for the treatment of muscular disease.
Project description:Adult skeletal muscle stem cells, also known satellite cells (SCs), are quiescent and activate in response to injury. However, the activation mechanisms of quiescent SCs (QSCs) remain largely unknown. Here, we investigated the metabolic regulation of SC activation by identifying regulatory metabolites that promote SC activation. Using targeted metabolomics, we found that spermidine acts as a regulatory metabolite to promote SC activation and muscle regeneration in mice. Mechanistically, spermidine activates SCs via generating hypusinated eIF5A. Using SC-specific eIF5A-knockout (KO) and Myod-KO mice, we further found that eIF5A is required for spermidine-mediated SC activation by controlling MyoD translation. More significantly, depletion of eIF5A in SCs results in impaired muscle regeneration in mice. Together, the findings of our study define a novel mechanism that is essential for SC activation and acts via spermidine-eIF5A-mediated MyoD translation. Our findings suggest that the spermidine-eIF5A axis represents a promising pharmacological target in efforts to activate endogenous SCs for the treatment of muscular disease.
Project description:Adult skeletal muscle stem cells, also known satellite cells (SCs), are quiescent and activate in response to injury. However, the activation mechanisms of quiescent SCs (QSCs) remain largely unknown. Here, we investigated the metabolic regulation of SC activation by identifying regulatory metabolites that promote SC activation. Using targeted metabolomics, we found that spermidine acts as a regulatory metabolite to promote SC activation and muscle regeneration in mice. Mechanistically, spermidine activates SCs via generating hypusinated eIF5A. Using SC-specific eIF5A-knockout (KO) and Myod-KO mice, we further found that eIF5A is required for spermidine-mediated SC activation by controlling MyoD translation. More significantly, depletion of eIF5A in SCs results in impaired muscle regeneration in mice. Together, the findings of our study define a novel mechanism that is essential for SC activation and acts via spermidine-eIF5A-mediated MyoD translation. Our findings suggest that the spermidine-eIF5A axis represents a promising pharmacological target in efforts to activate endogenous SCs for the treatment of muscular disease.