Collagen VI is a conserved pro-fibrotic signal disrupting muscle regeneration across distinct human myopathies

Muscle fibrosis is a major driver of progression in diverse myopathies, yet the conserved molecular mediators of this process in humans remains poorly defined. Here, we identify collagen VI as a common pro-fibrotic and regeneration-impairing extracellular matrix (ECM) component across three distinct human myopathies: Duchenne Muscular Dystrophy (DMD), Oculopharyngeal Muscular Dystrophy (OPMD), and Inclusion Body Myositis (IBM). Proteomic profiling of fibrotic biopsies revealed consistent upregulation of collagen VI and laminin {gamma}1, alongside disease-specific alterations involving other ECM proteins. Fibro-adipogenic progenitors (FAPs) are the predominant source of these ECM components, including collagen VI and laminin {gamma}1. Functionally, xenotransplantation of patient-derived FAPs into regenerating mouse muscle induced localized collagen deposition, myofiber atrophy, and depletion of Pax7 muscle stem cells. Mechanistic assays demonstrated that FAP-derived collagen VI is sufficient to impair myogenic fusion, while silencing COL6 in patient FAPs restores fusion capacity, directly linking pathological collagen VI deposition to regeneration failure. Our findings uncover collagen VI as a conserved effector of fibrosis and stem cell niche disruption in human myopathies, positioning it as a potential therapeutic target across genetically and clinically distinct muscle diseases.