Limb Regeneration in Amphibians

Among vertebrates, many amphibians have the unique ability to regenerate complete and fully functional limbs following amputation. The early events characterizing this process have some similarity to wound healing in terrestrial animals but with more tightly regulated inflammation and other differences that allow the limb stump to avoid scarring and establish tissue interactions that lead to a regeneration blastema, a self-organizing structure out of which the new limb develops. In addition to the activities of an epithelial–mesenchymal interaction and growth factor gradients, axons entering the early blastema from nerves of the limb stump are also required for blastema growth, a requirement not present during the development of the embryonic limb bud. This review summarizes the major features of the limb regeneration process and discusses briefly the decline of regenerative capacity in higher vertebrates.