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Fibro-Adipogenic Progenitor cells from murine SMA muscles are intrinsically adipogenic

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE322566 | GEO | 2026/03/05

REPOSITORIES: GEO

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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

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)

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Fibro-Adipogenic Progenitor cells from murine SMA muscles are intrinsically adipogenic

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