Many animals, notably salamanders, axolotls, starfish &etc are able to regrow limbs which have been lost to accidents or disease. Although mammals can regrow various tissues (notably skin, liver and tail tips) there is no capacity to regrow limbs etc. If this could somehow be 'turned on' it would be of huge benefit to amputees etc. At present the biological mechanisms which control for regrowth are unknown.
Regeneration remains one of nature’s most exciting mysteries.Several organisms can regenerate diverse parts of their bodies with different efﬁciencies. Although important progress in the understanding of this phenomenon has been made in the last decades, the precise spatio-temporal cellular dynamics of the regenerative response remains an unresolved puzzle.
Source: Developmental Biology, Volume 461, Issue 2, May 2020
Several versions of 'Regenerative Medicine' are currently under development - with various drugs being tested for their potential to induce regrowth. None is as yet in routine use.
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