A quantitative study of the muscle satellite cells in various neuromuscular disorders.

The regenerative ability of muscles was studied in various neuromuscular disorders by quantitative electron microscopy using two indices of both the satellite cell population and the euchromatin percentage of satellite cell nucleus. Both the number of satellite cells and the euchromatin percentage were increased in polymyositis. Duchenne muscular dystrophy and myotonic dystrophy showed only an increased number of satellite cells without increased euchromatin percentage, while amyotrophic lateral sclerosis had only an increased euchromatin percentage without increased satellite cell number. These results suggest that some defects of satellite cell function probably exist in progressive muscular dystrophy and amyotrophic lateral sclerosis, while in polymyositis the muscle fiber may have the ability to regenerate completely. The euchromatin percentages of myonuclei were increased in polymyositis and Duchenne muscular dystrophy, but not in amyotrophic lateral sclerosis or myotonic dystrophy compared to those of controls. This suggests the activated function of the remaining muscle fibers in polymyositis and Duchenne muscular dystrophy.