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The Fosl1-Kdm6b Axis Controls Skeletal Muscle Fibrosis by Regulating Histone H3K27me3 [Cut&Tag]

ABSTRACT: Skeletal muscle fibrosis, characterized by the replacement of functional muscle tissue with fibrotic scarring, leads to muscle function loss and potentially fatal respiratory failure, particularly in muscular dystrophy. The mechanisms driving muscle fibrosis is not yet fully understood. Our study utilized single-cell RNA-seq and single-nuclei ATAC-seq to analyze the transcriptome and chromatin accessibility of regenerating and dystrophic skeletal muscle, identifying a specific subset of fibro-adipogenic precursors (FAPs) enriched in dystrophic muscles, termed fibrotic FAPs. We further demonstrated that chronic inflammation upregulates Fosl1, an early response gene, which activates the expression of Kdm6b in fibrotic FAPs. Kdm6b, a histone demethylase, specifically removes the repressive histone H3K27me3 mark. Notably, targeting Kdm6b genetically and pharmacologically inhibits fibrotic di^erentiation in human and mouse FAPs in vitro and ameliorated muscle fibrosis in mouse models in vivo. Furthermore, constitutive activation of the Fosl1-Kdm6b pathway reduced H3K27me3 modification at critical fibrotic gene loci, leading to their transcriptional activation. Taken together, our findings reveal that chronic inflammation perpetuates the Fosl1-Kdm6b axis in FAPs, causing epigenomic reprogramming and altering the H3K27me3 landscape, which is essential for preventing fibrotic di^erentiation of FAPs and skeletal muscle fibrosis.

ORGANISM(S): Mus musculus

PROVIDER: GSE275142 | GEO | 2025/02/28

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