High regenerative ability of tailed amphibians (Urodela) as a result of the expression of juvenile traits by mature animals

The highest potencies of regeneration in tailed amphibians in comparison with the abilities of organ and tissue restoration in other vertebrates represent the goal of longstanding and intense studies. Accumulated information can half-open some mysteries of cellular and molecular fundamentals of regeneration in Urodela, but it does not explain the maintenance of regenerative abilities in mature, adult animals. The information summarized in the review suggests that the paedomorphosis inherent in this animal group determines the keeping of the juvenile state on all levels of organization—from organismic to molecular. This, in turn, permits and eases initiation and development of regenerative responses to trauma, right up to the epimorphic regeneration of whole organs. As an example, we have traced paedomorphosis-associated cellular and molecular specificities of urodelean eye and brain tissues, which could possibly play a permissive role in their complete regeneration.