A discrepancy resolved: human satellite cells are not preprogrammed to fast and slow lineages

Satellite cells from chicken and mouse muscle when differentiated in vitro have been shown to display a myosin heavy chain phenotype that corresponds to the fibre from which they originated. Indirect evidence has suggested th at this might not be the case for human satellite cells. In the present stu dy we have compared the myosin heavy chain (MHC) profile expressed by diffe rentiated cultures of satellite cells isolated from single fast or slow mus cle fibres. The MHC composition of the isolated fibres was determined by so dium dodecyl sulfate glycerol gel electrophoresis and Western blotting. The MHC profile expressed by the differentiated myotubes was identified by imm unostaining using specific antibodies. Our results show that all human sate llite cells isolated from either fast or slow fibres form myotubes in vitro which co-express both fast and slow MHCs independently of the fibre type f rom which they originated. These results confirm that human satellite cells , in contrast to those of birds and rodents, are not confined to distinct f ast and slow lineages. (C) 2001 Elsevier Science B.V. All rights reserved.