By Eve Herold –
Axolotls (Ambystoma mexicanum) have more than their cute looks going for them. The small, amphibious creatures, which resemble pinkish salamanders and always look like they’re smiling, have the ability to regenerate whole limbs in the event of injury. This is thanks to specialized cells that “know” just which part needs to be regenerated, and where. In a paper published in Nature Communications, researchers at Northeastern University and the University of Kentucky report that they’ve identified a molecule—retinoic acid—that’s distributed throughout the bodies of axolotls in varying amounts that cue regenerative cells to spring into action, regrowing severed limbs. Could humans harness this ability, given that we too harbor retinoic acid cells? One danger would be the body’s cells triggering haphazard regeneration, resulting in a bizarre mishmash of limbs and tissues, but the humble axolotl has solved this problem by creating the proper ratio of retinoic acid to an enzyme that dissolves it, preventing overgrowth. In addition, the creature’s distribution of retinoic acid appears in gradations, with more of it close to the body and a diminishing amount along the limbs so that they harbor the right amount of it to grow just the missing part and no more. Regenerated axolotl limbs contain the right cell types to compose the limb since combinations of cells work together to form nerve, muscle, tendon and other vital tissues to create a working limb. What other tricks might the axolotl have up its figurative sleeve?