Ultrastructural evidence of "abortive" regeneration in murine muscular dystrophy.

Triceps and gastrocnemius muscles from dystrophic (129 ReJ dy/dy) and normal mice were examined by electron microscopy at different stages in development (birth to 6 months). A qualitative assessment was made of the incidence and success of regeneration. Mitotic figures were seen in satellite cells in two-week-old dystrophic muscle. Well-differentiated myotubes were seen in dystrophic muscles at all ages but the incidence of regeneration was greatly reduced in the older dystrophic muscles. Myotubes in areas of regeneration up to two months of age frequently showed atypical or degenerative features. It is concluded that regeneration of dystrophic mouse muscle proceeds normally to the myotube stage after which differentiation becomes aberrant and degeneration may occur. This "abortive" regeneration probably contributes to the progression of the myopathy.