A quantitative comparison of satellite cell ultrastructure in Duchenne muscular dystrophy, polymyositis, and normal controls.

Failure of the muscle to regenerate successfully is an important feature of the pathology of Duchenne muscular dystrophy (DMD). It is known that this is not due to a numerical reduction in the population of satellite cells. We have therefore examined the ultrastructural composition of the satellite cells in 25 DMD cases and compared them with satellite cells from normal subjects and from polymyositis patients to try to identify morphological features that might be associated with an impaired developmental competence. Profiles of randomly and serially sectioned satellite cells were analyzed stereologically to obtain nuclear and cytoplasmic areas. Within the cytoplasm, the areas occupied by mitochondria, rough endoplasmic reticulum (RER), and Golgi apparatus were measured. Micropinocytotic vesicles (MPVs) at the periphery of the cells were counted. The nucleus to cytoplasm ratios and mitochondrial, RER, and Golgi volume fractions were not significantly different in the three satellite cell samples. The cells in the DMD sample contained more MPVs than those in the normal subjects. This is attributed to a generalized cell response to a physiologically altered environment in the diseased muscle.