Background: The circadian clock plays a key role in muscle stem cell behavior that promotes regenerative myogenesis and clock dysregulation is implicated in muscular dystrophy, suggesting its potential as a target for dystrophic disease therapy.
Objective: Leveraging a genetic gain-of-function approach together with development of clock-activating molecules, here we demonstrate the protective effects of augmenting clock function against muscular dystrophy, and importantly, the pre-clinical therapeutic efficacy of a novel clock activator in preventing muscle damage and restoring muscle function.
Results: In a satellite cell-specific knock-in model, genetic augmentation of clock function prolonged satellite cell proliferative expansion with enhanced myogenic progression to promote muscle regeneration. In the dystrophic background, enhancing clock function was sufficient to protect against muscle injury with restoration of function. Mechanistically, in addition to its pro-myogenic action, clock exerts direct transcriptional control to induce integral components of dystrophin glycoprotein complex (DGC), including Utrophin, alpha-sarcoglycan and Dystrobrevin, along with re-enforcing membrane linkage with extracellular matrix via induction of Integrin beta-1, thereby restoring sarcolemma stability to target the primary etiology of muscular dystrophy. Furthermore, optimization of a hit molecule identified from a clock modulator screen uncovered the clock-activating lead compound, CM002, that displayed improved pro-myogenic efficacy in dystrophic myoblasts with robust induction of DGC components. CM002 augmented regenerative myogenesis with enhanced nascent myofiber formation upon muscle injury. Most importantly, CM002 administration in mdx mice led to marked protection against global injury with restoration of sarcolemma-ECM stability, accompanied with significantly improved muscle function and exercise capability. Lastly, we show that CM002 was sufficient to enhance myogenic induction and DGC in human DMD myoblasts, supporting its translational potential for DMD therapy.
Conclusion: Collectively, our study revealed that targeting clock function to rescue the primary membrane defect while enhancing regenerative capacity could be a promising approach for dystrophic disease therapy.