New approaches to amphibian limb regeneration

Limb regeneration in urodele amphibians proceeds by the formation of a blastema, a growth zone of mesenchymal progenitor cells. Here, I review the origin of the blastema and its positional identity. The ability to culture and reimplant newt blastemal cells, and to transfect them in culture and in situ using a particle delivery system, has yielded new information about the action of retinoic acid on the blastema and the reversal of muscle differentiation during limb regeneration.