Role of dystrophin deficiency in fibrosis-related gene expression during myogenesis

Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and fibrosis, primarily driven by excessive extracellular matrix (ECM) deposition. TGF-β cytokines and their associated latent TGF-β binding proteins (LTBPs) are key regulators of ECM composition and remodeling. While the roles of these molecules in skeletal muscle fibrosis are well established, the contributions of myoblasts to their production and the effects of dystrophin deficiency on their expression remain unclear. This study aimed to investigate the impact of dystrophin deficiency on myogenesis and the expression dynamics of fibrosis-related genes using wild-type (WT) and dystrophin-deficient (mdx) H2K myoblasts. Myogenesis was investigated through three key stages: proliferation, fusion, and terminal differentiation, by assessing both morphological changes and the expression levels of Tgfb and Ltbp genes at each stage. Dystrophin deficiency did not impair the morphological progression or timing of myogenesis, as mdx cells displayed comparable differentiation patterns to WT cells in terms of myotube formation, length, and alignment. However, dystrophin deficiency significantly altered the expression profiles of Tgfb and Ltbp genes. Notably, Tgfb3 expression was consistently elevated in mdx cells across all stages, reaching a 4.26-fold increase during proliferation and 2.0-fold during terminal differentiation. In contrast, the expression of Ltbp1, Ltbp3, and Ltbp4 was initially reduced in mdx cells but increased significantly in terminally differentiated myotubes. These findings reveal that dystrophin deficiency does not disrupt myogenesis morphologically or temporally but significantly impacts the expression of key fibrosis-related genes. This suggests that altered Tgfb and Ltbp expression dynamics may contribute to ECM accumulation and fibrosis in DMD, providing potential targets for therapeutic interventions.