Plasticity and recovery of skeletal muscle satellite cells during limb regeneration

Salamander limb regeneration depends on local progenitors whose progeny are recruited to the new limb. We previously identified a Pax7+ cell population in skeletal muscle whose progeny have the potential to contribute to the regenerating limb. However, the plasticity of individual Pax7+ cells, as well as their recovery within the new limb, was unclear. Here, we show that Pax7+ cells remain present after multiple rounds of limb amputation/regeneration. Pax7+ cells are found exclusively within skeletal muscle in the regenerating limb and proliferate where the myofibers are growing. Pax7 is rapidly down-regulated in the blastema, and analyses of clonal derivatives show that Pax7+ cell progeny are not restricted to skeletal muscle during limb regeneration. Our data suggest that the newt regeneration blastema is not entirely a composite of lineage-restricted progenitors. The results demonstrate that except for a transient and subsequently blunted increase, skeletal muscle satellite cells constitute a stable pool of reserve cells for multiple limb regeneration events.—Morrison, J. I., Borg, P., Simon, A. Plasticity and recovery of skeletal muscle satellite cells during limb regeneration. FASEB J. 24, 750–756 (2010). www.fasebj.org