An electron microscopic study of satellite-cells and regeneration in dystrophic mouse muscle

Triceps and gastrocnemius muscles from dystrophic (129 Rej dy/dy) and normal mice were examined by electron microscopy at different stages in development for evidence of regeneration. Mitotic satellite cells were present only in dystrophic muscle. Myoblasts containing myofilaments, and multinucleate myotubes were observed within foci of regeneration. Approximately 50% of the myotubes showed features indicative of degeneration or abnormal development. These features included the presence of membrane whorls, and myofibrillar and sarcolemma breakdown. Quantitative studies suggest that the number of satellite cells is increased in dystrophic muscle. It is concluded that there are sufficient satellite cells in dystrophic mouse muscle to allow regeneration, and they are able to proliferate and form well differentiated myotubes. However, subsequent development of the myotubes can be ineffective, or 'abortive', reducing the regeneration capacity to the muscle.