Resident mesenchymal progenitor cells require autocrine IGF-I in homeostatic and regenerating skeletal muscle
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE332757 | GEO | 2026/05/26
REPOSITORIES: GEO
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Project description:Fibro-Adipogenic Progenitors (FAPs) are mesenchymal progenitor cells vital for muscle homeostasis and regeneration, but they also produce fibrosis and differentiate into intramuscular fat under pathological conditions. Insulin-like Growth Factor-I (IGF-I), a key regulator of muscle repair, influences satellite cell activity, macrophage polarization, and extracellular matrix (ECM) remodeling. Although FAPs are a major source of IGF-I in muscle, its specific role remains unclear. Thus, we generated inducible FAP-specific Igf1 knockout mice (FID mice) to determine the necessity of the FAP IGF-I source. After acute BaCl2 injury, FID mice exhibited impaired muscle regeneration, characterized by fewer Pax7+ cells, increased CD68+ macrophage accumulation, smaller fibers with lower proportions of EmbMHC+ fibers, and reduced ECM content compared to controls. FAP proliferation was impaired, with fewer total and Ki67+ FAPs in regenerating muscles from FID mice. Following glycerol injury, muscles from FID mice exhibited reduced adipocyte accumulation. To probe the autocrine role of FAP IGF-I, we isolated FAPs from muscles 3 days post-injury. Primary FAPs isolated from FID mice had blunted growth, accompanied by upregulation of immune-regulatory genes and downregulation of ECM and cell proliferation genes by RNASeq. Additionally, cultured FID FAPs had delayed differentiation and sustained PDGFRα expression in response to TGF-β, as well as impaired adipocyte differentiation in adipogenic media. Finally, FID FAPs entered a senescent state shortly after Cre recombination, showing high β-Gal expression in vivo and in vitro, and suppression of IGF-IR and IGF-I-dependent pathways. Taken together, our findings demonstrate that IGF-I derived from FAPs is a critical autocrine factor, with its absence leading to impaired function of FAPs for maintenance of muscle regenerative capacity
2025-11-19 | GSE282309 | GEO
Project description:Fibro adipogenic progenitors (FAPs) promote satellite cell differentiation in adult skeletal muscle regeneration. However, in pathological conditions, FAPs are responsible for fibrosis and fatty infiltrations. Here we show that the NOTCH pathway negatively modulates FAP differentiation both in vitro and in vivo. However, FAPs isolated from young dystrophin- deficient mdx mice are insensitive to this control mechanism. An unbiased mass spectrometry-based proteomic analysis of FAPs from muscles of wild type and mdx mice, suggest that the synergistic cooperation between NOTCH and inflammatory signals controls FAP differentiation. Remarkably, we demonstrated that factors released by hematopoietic cells restore the sensitivity to NOTCH adipogenic inhibition in mdx FAPs. These results offer a basis for rationalizing pathological ectopic fat infiltrations in skeletal muscle and may suggest new therapeutic strategies to mitigate the detrimental effects of fat depositions in muscles of dystrophic patients.
2019-06-24 | PXD014195 | Pride
Project description:Fatty infiltration, the ectopic deposition of adipose tissue within skeletal muscle, is mediated via the adipogenic differentiation of fibro-adipogenic progenitors (FAPs). We used single-nuclei and single-cell RNA sequencing to characterize FAP heterogeneity in patients with fatty infiltration. We identified an MME+ FAP subpopulation which, based on ex vivo characterization as well as transplantation experiments, exhibits high adipogenic potential. MME+ FAPs are characterized by low activity of WNT, known to control adipogenic commitment, and are refractory to the inhibitory role of WNT activators. Using preclinical models for muscle damage versus fatty infiltration, we show that many MME+ FAPs undergo apoptosis during muscle regeneration and differentiate into adipocytes under pathological conditions, leading to their depletion. Finally, we utilized the varying fat infiltration levels in human hip muscles to show the depletion of MME+ FAPs in fatty infiltrated human muscle. Altogether, we have identified the dominant adipogenic FAP subpopulation in skeletal muscle.
2023-01-18 | GSE200487 | GEO
Project description:Utilizing glycerol intramuscular injections in M. musculus provides a model of skeletal muscle damage followed by skeletal muscle regeneration. In particular, glycerol-induced muscle injury triggers accute activation of muscle Fibro/Adipogenic Progenitors, also called FAPs. However, aging dramatically impairs FAP function. We characterized genome-wide expression profiles of young and old FAPs in the non-proliferative and activated state, freshly isolated to non-injured or damaged muscles, respectively. Our goal was to uncover new regulatory signalings specific to FAP entry into the activation program that are affected with age.
2018-11-26 | GSE92508 | GEO
Project description:During aging, the number and functionality of muscle stem cells (MuSCs) decreases leading to impaired regeneration of aged skeletal muscle. In addition to intrinsic changes in aged MuSCs, extracellular matrix (ECM) proteins deriving from other cell types, e.g., fibrogenic-adipogenic progenitor cells (FAPs), contribute to the aging phenotype of MuSCs and impaired regeneration in the elderly. So far, no comprehensive analysis on how age-dependent changes in the whole skeletal muscle proteome affect MuSC function have been conducted. Here, we investigated age-dependent changes in the proteome of different skeletal muscle types by applying deep quantitative mass spectrometry. We identified 183 extracellular matrix proteins that show different abundances in skeletal muscles of old mice. By integrating single cell sequencing data, we reveal that transcripts of those ECM proteins are mainly expressed in FAPs, suggesting that FAPs are the main contributors to ECM remodelling during aging. We functionally investigated one of those ECM molecules, namely Smoc2, which is aberrantly expressed during aging. We show that Smoc2 levels are elevated during regeneration and that its accumulation in the aged MuSC niche causes impairment of MuSCs function through constant activation of integrin/MAPK signaling. In vivo, supplementation of exogenous Smoc2 hampers the regeneration of young muscles following serial injuries, leading to a phenotype reminiscent of regenerating aged skeletal muscle. Taken together, we provide a comprehensive resource of changes in the composition of the ECM of aged skeletal muscles, we pinpoint the cell types driving these changes, and we identify a new niche protein causing functional impairment of MuSCs thereby hampering the regeneration capacity of skeletal muscles.
2021-11-25 | PXD015728 | Pride
Project description:During aging, the number and functionality of muscle stem cells (MuSCs) decreases leading to impaired regeneration of aged skeletal muscle. In addition to intrinsic changes in aged MuSCs, extracellular matrix (ECM) proteins deriving from other cell types, e.g., fibrogenic-adipogenic progenitor cells (FAPs), contribute to the aging phenotype of MuSCs and impaired regeneration in the elderly. So far, no comprehensive analysis on how age-dependent changes in the whole skeletal muscle proteome affect MuSC function have been conducted. Here, we investigated age-dependent changes in the proteome of different skeletal muscle types by applying deep quantitative mass spectrometry. We identified 183 extracellular matrix proteins that show different abundances in skeletal muscles of old mice. By integrating single cell sequencing data, we reveal that transcripts of those ECM proteins are mainly expressed in FAPs, suggesting that FAPs are the main contributors to ECM remodelling during aging. We functionally investigated one of those ECM molecules, namely Smoc2, which is aberrantly expressed during aging. We show that Smoc2 levels are elevated during regeneration and that its accumulation in the aged MuSC niche causes impairment of MuSCs function through constant activation of integrin/MAPK signaling. In vivo, supplementation of exogenous Smoc2 hampers the regeneration of young muscles following serial injuries, leading to a phenotype reminiscent of regenerating aged skeletal muscle. Taken together, we provide a comprehensive resource of changes in the composition of the ECM of aged skeletal muscles, we pinpoint the cell types driving these changes, and we identify a new niche protein causing functional impairment of MuSCs thereby hampering the regeneration capacity of skeletal muscles.
2021-11-25 | PXD015616 | Pride
Project description:In human dystrophies, the progressive muscle wasting is exacerbated by ectopic deposition of fat and fibrous tissue originating from fibro/adipogenic progenitors (FAPs). In degenerating muscles, the ability of these cells to adjuvate a successful healing is attenuated and FAPs aberrantly expand and differentiate into adipocytes and fibroblasts. Thus, arresting the fibroadipogenic fate of FAPs, without affecting their physiological role, represents a valuable therapeutic strategy for patients affected by muscle diseases. Here, using a panel of adipose progenitor cells including human-derived FAPs coupled with pharmacological perturbations and proteome profiling, we report that LY2090314 interferes with a genuine adipogenic program acting as WNT surrogate for the stabilization of a competent -catenin transcriptional complex. To predict the beneficial impact of LY2090314 in limiting ectopic deposition of fat in human muscles, we combined the Poly-Ethylene-Glycol-Fibrinogen biomimetic matrix with these progenitor cells to create a miniaturized 3D model of adipogenesis. Using this scalable system, we demonstrated that a two-digit nanomolar dose of this compound is effective to repress adipogenesis in a higher 3D scale, thus offering a concrete proof for the use of LY2090314 to limit FAP-derived fat infiltrates in dystrophic muscles.
2023-06-13 | PXD040479 | Pride
Project description:Fibro-adipogenic progenitors (FAPs) are emerging cellular components of the skeletal muscle regenerative environment. The alternative functional phenotype of FAPs - either supportive of muscle regeneration or promoting fibro-adipogenic degeneration - is a key determinant in the pathogenesis of muscular diseases, including Duchenne Muscular Dystrophy (DMD). However, the molecular regulation of FAPs is still unknown. We show here that an "HDAC-myomiR-BAF60 variant network" regulates the functional phenotype of FAPs in dystrophic muscles of mdx mice. Combinatorial analysis of gene expression microarray and genome-wide chromatin remodeling by Nuclease accessibility (NA)-seq revealed that HDAC inhibitors de-repress a "latent" myogenic program in FAPs from dystrophic muscles at early stages of disease progression. In these cells HDAC inhibition promoted the expression of two core components of the myogenic transcriptional machinery, MyoD and BAF60C, and upregulated the myomiRs (miRs) miR-1.2, miR-133 and miR-206, which target two alternative BAF60 variants (BAF60A and B) ultimately leading to the activation of a pro-myogenic program at the expense of the fibro-adipogenic phenotype. By contrast, FAPs from dystrophic muscles at late stages of disease progression displayed resistance to HDACi-induced chromatin remodeling at myogenic loci and fail to activate the pro-myogenic phenotype. These results reveal a previously unappreciated disease stage-specific bipotency of mesenchimal cells within the regenerative environment of dystrophic muscles. Resolution of such bi-potency by epigenetic interventions, such as HDACi, provides the molecular rationale for the in situ reprogramming of target cells to promote therapeutic regeneration of dystrophic muscles. miRNA modulation upon Histone Deacetylase inhibition in Fibro-Adipogenic Progenitors (FAPs) derived from young mdx mice was evaluated by small RNA-sequencing in 2 controls and 2 treated samples
2014-04-23 | E-GEOD-51933 | biostudies-arrayexpress
Project description:Fibro-adipogenic progenitors (FAPs) are emerging cellular components of the skeletal muscle regenerative environment. The alternative functional phenotype of FAPs - either supportive of muscle regeneration or promoting fibro-adipogenic degeneration M-bM-^@M-^S is a key determinant in the pathogenesis of muscular diseases, including Duchenne Muscular Dystrophy (DMD). However, the molecular regulation of FAPs is still unknown. We show here that an M-bM-^@M-^\HDAC-myomiR-BAF60 variant networkM-bM-^@M-^] regulates the functional phenotype of FAPs in dystrophic muscles of mdx mice. Combinatorial analysis of gene expression microarray and genome-wide chromatin remodeling by Nuclease accessibility (NA)-seq revealed that HDAC inhibitors de-repress a M-bM-^@M-^\latentM-bM-^@M-^] myogenic program in FAPs from dystrophic muscles at early stages of disease progression. In these cells HDAC inhibition promoted the expression of two core components of the myogenic transcriptional machinery, MyoD and BAF60C, and upregulated the myomiRs (miRs) 1.2, 133 and 206, which target two alternative BAF60 variants (BAF60A and B) ultimately leading to the activation of a pro-myogenic program at the expense of the fibro-adipogenic phenotype. By contrast, FAPs from dystrophic muscles at late stages of disease progression displayed resistance to HDACi-induced chromatin remodeling at myogenic loci and fail to activate the pro-myogenic phenotype. These results reveal a previously unappreciated disease stage-specific bipotency of mesenchimal cells within the regenerative environment of dystrophic muscles. Resolution of such bi-potency by epigenetic interventions, such as HDACi, provides the molecular rationale for the in situ reprogramming of target cells to promote therapeutic regeneration of dystrophic muscles. Genome-wide chromatin accessibility patterns in FAPs cells derived from mdx mice at different ages treated either with HDAC inhibitor Trichostatin A (TSA) or with vehicle (saline solution) were assessed using NA-seq (PMID: 19289091)
2014-04-02 | E-GEOD-52062 | biostudies-arrayexpress
Project description:Spinal muscular atrophy is a neurodegenerative disorder caused by mutations in the SMN1 gene. Although classically viewed as a neurogenic disease, SMA patients exhibit poor skeletal muscle regeneration and increased fatty-fibrotic infiltration. Fibro-Adipogenic progenitors are mesenchymal precursor cells that contribute to muscle remodeling and underly fat and fibrosis formation. Because FAPs transiently express Smn1 during regeneration, FAPs were examined in muscles from adult SMA and control mice to determine if reduced Smn activity altered their properties. We performed a non-biased screen of FAPs following BaCl2-induced injury using an in-situ cell surface proteomic strategy that probed the cellular membrane and environment of FAPs in early regeneration. Proteomic profiling revealed early adipogenic priming in SMA tissues, with increased levels of perilipin-4 and adipocyte lipid-binding proteins. Significantly more adipocytes accumulated in SMA muscles after glycerol injection versus controls. Further, SMA FAPs produced more fat than control FAPs when transplanted into glycerol injured muscles lacking FAPs. RNA sequencing of FAPs isolated after BaCl2 or glycerol injury identified transcriptional enrichment of lipid biosynthesis and dysregulated lipid metabolism in SMA FAPs. Primary FAPs isolated from SMA muscles mirrored heightened adipocyte formation, which was normalized by increasing Smn activity with Risdiplam. Conversely, adipogenesis of primary FAPs from control muscles was enhanced when subjected to siRNA Smn1 knockdown. Together, these findings demonstrate that reduced Smn activity potentiates intrinsic adipogenic bias in FAPs that may contribute to pathological fat deposition in SMA muscle.
2026-03-05 | GSE322566 | GEO