Abstract
Purpose:
To investigate whether differences in muscle stem cells / satellite cells (SC) are the basis for the relative sparing of the EOMs in amyotrophic lateral sclerosis (ALS).
Methods:
Extraocular muscles (EOM) and upper and lower limb muscles from 8 ALS patients were investigated with a immunohistochemical method especially designed to reliably identify satellite cells and other muscle progenitor cells in human tissue, using multiple labeling with Pax7, NCAM, laminin and DAPI in the same muscle cross-section.
Results:
Over 20 000 muscle fibers in the EOMs (mean 1631 muscle fibers / specimen) and over 3 200 fibers in the biceps brachii have been counted thus far. Lower limb specimens are under analysis. The EOMs showed mild signs of muscle pathology compared to the limb muscles and the biceps brachii appeared less affected than muscles from the lower limb. Pax7 positive cells were present in all samples. The number of Pax 7 positive cells / fiber in the EOMs of ALS donors was not statistically different from that of controls. Twelve percent of the Pax7 positive nuclei were found in cells located outside the SC niche in the EOMs. Important variation in the distribution of SCs was noted in the limb muscle samples.
Conclusions:
The human EOMs are far less affected than the limb mucles from the same patient. The EOMs maintained their SC content at the end stage of the disease. Further studies evaluating markers of satellite cell activation in human specimens and myonuclei turnover in animal models are under way to further elucidate the possible role of SC in the relative sparing of the EOMs in ALS.
Keywords: 521 extraocular muscles: structure •
638 pathology: human •
554 immunohistochemistry