Single cell analysis of muscle contracture in cerebral palsy reveals pro-fibrotic and anti-myogenic stem cell populations with altered cell-cell interactions

Development of muscle contractures are common in cerebral palsy (CP) and characterized by high muscle stiffness that limits function and mobility. However, the state of stem cells within contracture, particularly muscle stem cells and fibro-adipogenic progenitors, are 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 down regulation of myogenic genes compared to typically developing. Fibro-adipogenic progenitors in CP showed the emergence of a significant proportion of a highly profibrotic subpopulation, leading to the most dramatically up-regulated genes in CP also being extracellular matrix constituents. Interacting signals between fibro-adipogenic progenitors, muscle stem cells, and immune cells were identified that support contracture progression. Contracture reduces myogenic muscle stem cells and enhances fibrotic signals in muscle stem cells and fibro-adipogenic progenitors that perpetuate contracture. The study reveals specific genes and signaling pathways as therapeutic targets to reduce muscle contracture in children with CP.