A new look at the origin, function, and "stem-cell" status of muscle satellite cells

Muscle satellite cells have long been considered a distinct myogenic lineag e responsible for postnatal growth, repair, and maintenance of skeletal mus cle. Recent studies in mice, however, have revealed the potential for highl y purified hematopoietic stem cells from bone marrow to participate in musc le regeneration. Perhaps more significantly, a population of putative stem cells isolated directly from skeletal muscle efficiently reconstitutes the hematopoietic compartment and participates in muscle regeneration following intravenous injection in mice. The plasticity of muscle stem cells has rai sed important questions regarding the relationship between the muscle-deriv ed stem cells and the skeletal muscle satellite cells. Furthermore, the abi lity of hematopoietic cells to undergo myogenesis has prompted new investig ations into the embryonic origin of satellite cells. Recent developmental s tudies suggest that a population of satellite cells is derived from progeni tors in the embryonic vasculature. Taken together, these studies provide th e first evidence that pluripotential stem cells are present within adult sk eletal muscle. Tissue-specific stem cells, including satellite cells, may s hare a common embryonic origin and possess the capacity to activate diverse genetic programs in response to environmental stimuli. Manipulation of suc h tissue-specific stem cells may eventually revolutionize therapies for deg enerative diseases, including muscular dystrophy. (C) 2000 Academic Press.