Skeletal muscles in rodent models of Duchenne muscular dystrophy (DMD) and patient muscle samples exhibit signatures of cellular senescence that increase with disease severity. Since multiple cell types show markers of senescence in DMD muscle, understanding muscle cell-specific involvement has been difficult to dissect in vivo. To address this limitation, we created a tissue-engineered model of human skeletal muscle (“myobundles”) using muscle progenitor cells (MPCs) isolated from age-matched healthy (HLT) and DMD donors. Compared to HLT MPCs, DMD MPCs showed increased senescent markers, reduced proliferation, and impaired metabolic flux. In both 2D and 3D cultures, DMD MPCs exhibited decreased differentiation and fusion, while in 3D myobundles, DMD myofibers displayed pathological features, including increased branching, hypercontractions, and lipid droplet accumulation. Functional analyses revealed decreased amplitudes of contractile force and calcium transients in DMD myobundles, alongside greater susceptibility to fatigue and eccentric contraction damage.
Treatment of myobundles with prednisolone and vamorolone did not improve muscle force or fusion, while vamorolone reduced susceptibility to acute eccentric contraction damage. Notably, 7-day chronic electrical stimulation increased force generation in DMD tissues but also raised incidence of hypercontracted myofibers. Vamorolone, but not prednisolone, significantly reduced incidence of hypercontractions and resulted in enhanced force generation with electrical stimulation.
Notably, TGF-β inhibition and glucocorticoids were ineffective in rescuing fusion deficit in this senescent DMD model, contrasting with hiPSC-based DMD models. On the other hand, a targeted drug screen identified two drug classes that restored fusion and improved force generation in DMD tissues.
The senescent DMD myobundles provide a valuable platform to study altered MPC function in DMD and offer a foundation for development of targeted drug and gene therapies. Future studies will test therapeutic benefits of identified fusion restoration drugs in mouse models of disease.