Abstract
Skeletal muscle stem cells, also known as muscle satellite cells, are located adjacent to the plasma membrane of myofibers beneath the basement membrane. During muscle regeneration, satellite cells proliferate and then fuse together to form myotubes. Histopathologic analysis has shown that muscle satellite cells differentiate into myotubes and myofibers exclusively , and there has been no evidence that these cells are able to differentiate into nonmuscle cells in vivo. However, both primary cultured mouse myoblasts and the immortalized mouse myoblastic cell line C2C12 differentiate into osteoblasts and adipocytes as well as myotubes under appropriate culture conditions. Although these observations suggest that muscle satellite cells preserve multipotentiality, it has been unclear whether different fates are generated from a single satellite cell. We have now characterized a clone of unmanipulated myogenic cells derived from a single mouse muscle satellite cell and revealed its multipotentiality in vitro. Furthermore, multipotent progenitor cells derived from muscle satellite cells were shown to co-express multiple determination genes under growth conditions. On the basis of these observations, we propose a "stock options" model for the lineage commitment of muscle satellite cells. [Jpn J Physiol 54 Suppl:S54 (2004)]
