After 24-Hour Treatment, Frogs Started Regrowing Lost Limbs

Regeneration science has taken a big step—or hop—forward with an experiment that allowed frogs to regrow lost hind limbs. African clawed frogs lose their ability to regenerate limbs after they are tadpoles but scientists managed to get them to regrow a functional hind limb after a treatment that lasted just 24 hours, the New York Times reports. After amputating a hind limb from dozens of frogs, the amputation wounds were covered with a silicone cap that contained a cocktail of regenerative drugs. In a study published in the journal Science Advances, researchers say the treatment triggered an 18-month process in which the frogs regrew a functional, though not perfect, limb that responded to touch and could be used for swimming.

Study co-author Michael Levin, director of the Allen Discovery Center at Tufts University, tells the Times that like humans, adult frogs of the species can regenerate skin over a wound but scar tissue prevents further regrowth. He says the "BioDome" silicon cap served to inhibit scarring and "convince every cell in there that, 'OK, we're on the leg-growing program.'" The Guardian notes that while adult humans can regenerate some parts of their bodies, including the liver, and children can regrow fingertips, there's no natural way for mammals to regrow limbs—but researchers believe it could still be possible to tap into the ability to make complex body structures. The regrown frog limbs included bone, muscle, and nerves.

"The fact that it required only a brief exposure to the drugs to set in motion a months-long regeneration process suggests that frogs and perhaps other animals may have dormant regenerative capabilities that can be triggered into action," says lead study author Nirosha Murugan, who conducted the research in Levin's lab. Researchers say that while much more work needs to be done before any similar treatment is attempted on human patients, the initial attempt on frogs was far more successful than they expected. Levin says he has already started trials on mice. (This sea creature can regenerate its entire body.)