Single cell analysis of muscle contracture in cerebral palsy reveals profibrotic and antimyogenic stem cell populations with altered cell-cell interactions.

Development of muscle contractures is common in cerebral palsy (CP) and is characterized by high muscle stiffness that limits function and mobility. However, the state of stem cells within contracture, particularly muscle stem cells and fibroadipogenic progenitors, is largely unknown. This study leverages single cell RNA sequencing technology to determine how specific cell types are altered in the contracture environment. Skeletal muscle biopsies were collected from children with CP or typically developing (TD) children undergoing surgery. The 10X Genomics platform was used on tissue from n = 3 patients per condition. Significant changes in CP compared to TD were investigated within individual cell types for differentially expressed genes, gene ontologies, cell subpopulations, and predicted interactions. CP muscle stem cells demonstrated significant upregulation of fibrotic genes and downregulation of myogenic genes compared to typically developing. Fibroadipogenic progenitors in CP showed the emergence of a significant proportion of a highly profibrotic subpopulation, leading to the most dramatically upregulated genes in CP also being extracellular matrix constituents. Interacting signals between fibroadipogenic progenitors, muscle stem cells, and immune cells were identified that support contracture progression. Contracture is associated with reduced myogenic transcriptional features in muscle stem cells and enhances fibrotic signals in muscle stem cells and fibroadipogenic progenitors that perpetuate contracture. The study reveals specific genes and signaling pathways as therapeutic targets to reduce muscle contracture in children with CP.NEW & NOTEWORTHY The development of skeletal muscle contractures in cerebral palsy is a major component of disability. However, little is known about how contracture influences stem cells. This study is the first to apply single cell RNA sequencing technology to muscle contractures of children with cerebral palsy. The analysis reveals muscle stem cells with reduced myogenic transcription. Critically, a profibrotic subpopulation of fibroadipogenic progenitors is revealed in contracture. Additionally, cell-cell signaling analysis identifies potential therapeutic targets.