Maturational defect of regenerating muscle fibers in cases with Duchenne and congenital muscular dystrophies.

Immature fibers in Duchenne muscular dystrophy (DMD) and congenital muscular dystrophies (CMD) were compared with human fetal muscles and experimentally-induced regenerating muscle fibers using the acridine orange (AO) technique on fluorescent microscopy and histochemical methods. Strong AO activity was observed on immature fibers in dystrophies and on experimentally-induced fibers in the early stages of regeneration. These young fibers showed type 2C histochemical reactions on ATPase stains. Human fetal muscles failed to show these fibers which were seen in the muscular dystrophies and the experimental regenerating muscle. From these results it is concluded that immature fibers in muscular dystrophies are early stages of regenerating fibers and not maturationally arrested fetal muscle fibers. In addition, these immature fibers formed small groups composed of 10 to 50 fibers in muscular dystrophies and sometimes large groups in CMD. It is suggested that the investigation of immature fibers and their grouping is quite important for revealing the pathogenesis of the muscular dystrophies.