Compartment-specific remodeling of skeletal muscle in Duchenne muscular dystrophy

Background: Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration accompanied by profound remodeling of muscle fiber type composition and metabolic capacity. Most studies, however, have analyzed bulk tissue or small biopsy samples, overlooking regional heterogeneity within individual muscles. This study aimed to characterize spatial patterns of fiber type remodeling in DMD muscles. Methods: We applied a multi-modal approach combining spatial transcriptomics, metabolic enzyme activity profiling, immunohistochemistry, and quantitative fiber-type analysis. Experiments were performed on phenotypically normal controls (Tg(Pax7-EGFP)15Tajb), dystrophic mice (hDMDdel52/mdx), and non-dystrophic genetic controls (hDMD/mdx). We mapped entire tibialis anterior muscles and extended analysis to the extensor digitorum longus and soleus. Statistical modeling assessed interactions between anatomical location and disease status, while standard tests were used for fiber-type comparisons. Results: Our findings reveal that DMD disrupts the normal organization of muscle metabolism. In healthy tibialis anterior muscle, oxidative fibers are more abundant in the center of the muscle, while glycolytic fibers are concentrated toward the ends. In DMD tibialis anterior muscle, this organization is lost, the central oxidative regions shrink, and histological examination further confirms decreased oxidative enzyme activity. Comparative analysis across tibialis anterior, extensor digitorum longus, and soleus muscles revealed consistent loss of MYH2-positive fibers. Additionally, we discovered that disease-related changes don't affect the muscle uniformly. Instead, different regions along the muscle show distinct patterns of tissue remodeling, immune cell infiltration, and scar tissue formation. Conclusions: This comprehensive mapping approach reveals that DMD progression creates a mosaic of different disease states within individual muscles. This spatially resolved framework advances our understanding of muscle remodeling and provides a foundation for biomarker discovery and therapeutic strategies that account for regional heterogeneity.