Skeletal myogenic progenitors originating from embryonic dorsal aorta coexpress endothelial and myogenic markers and contribute to postnatal muscle growth and regeneration

Skeletal muscle in vertebrates is derived from somites, epithelial structur es of the paraxial mesoderm, yet many unrelated reports describe the occasi onal appearance of myogenic cells from tissues of nonsomite origin, suggest ing either transdifferentiation or the persistence of a multipotent progeni tor. Here, we show that clonable skeletal myogenic cells are present in the embryonic dorsal aorta of mouse embryos. This finding is based on a detail ed clonal analysis of different tissue anlagen at various developmental sta ges. In vitro, these myogenic cells show the same morphology as satellite c ells derived from adult skeletal muscle, and express a number of myogenic a nd endothelial markers. Surprisingly, the latter are also expressed by adul t satellite cells. Furthermore, it is possible to clone myogenic cells from limbs of mutant c-Met-/- embryos, which lack appendicular muscles, but hav e a normal vascular system. Upon transplantation, aorta-derived myogenic ce lls participate in postnatal muscle growth and regeneration, and fuse with resident satellite cells. The potential of the vascular system to generate skeletal muscle cells may explain observations of nonsomite skeletal myogenesis and raises the possib ility that a subset of satellite cells may derive from the vascular system.