Regenerative capacity and the number of satellite cells in soleus muscles of normal and mdx mice

Satellite cells are potential myogenic cells that participate in repair and growth of muscle fibres. In this investigation, the change in the number o f satellite cells following severe muscle damage was monitored in soleus mu scle of age-matched mdx and C57B1/10 mice. Satellite cells were identified immunohistochemically in the light microscope by their association with a r ecently described marker protein, M-cadherin. and their location between th e muscle fibre's sarcolemma and the surrounding basal lamina. In cross-sect ions of untreated soleus muscle of C57B1/10 mice at 11-14.5 months of ape, nuclei of M-cadherin positive satellite cells on average amounted to 3.4%; of the total number of myonuclei. Surprisingly, significantly higher number s of satellite cell nuclei, both in absolute numbers (mean 24 +/- 11 versus 40 +/- 11 satellite cells per section) and relative to the total number of myonuclei (5.3%), were found in similarly aged animals in which severe mus cle damage had been inflicted 3-6 months before. Cross-sectional area, musc le tissue area and myonuclei counts had recovered to control values. In unt reated muscles of age-matched,,mir mice satellite cell counts: were not dif ferent (2.7% of myonuclei) from C57B1/10 mice. However, regeneration showed marked deficits, as there was a loss of about 36% total cross-sectional ar ea, about 48% total muscle fibre area and about 43% myonuclei per section c ompared to the untreated mdx muscles. Furthermore, the absolute number of s atellite cells decreased from 20 +/- 11 to 12 +/- 8 per section. The relati ve number of satellite cell nuclei remained comparable to, but did not exce ed. the undamaged muscles. The poor recovery of muscle and the missing post -regeneration rise in satellite cell number may indicate the reproductive l imits of the satellite pool. (C) 2000 Elsevier Science B.V. Ltd. All rights reserved.