Researchers at Tufts University and Harvard University’s Wyss Institute have regrowed amputated limbs. In a study published in Science Advances, the researchers showed how they used a chemical cocktail to induce limb growth in frogs.
Currently, limb regrowth is limited to “salamanders and superheroes,” the team said in a press release. Like humans, whose bodies cover large lesions with scar tissue, adult frogs are unable to naturally regenerate limbs.
For the study, the researchers began by applying a chemical cocktail with five substances infused in a silk protein gel on the stump of the African frogs and covering it in a silicone dome, which they call a BioDome, to seal it. They removed the dome after 24 hours – and then waited 18 months for the limb to grow back.
David Kaplan, Stern Family Professor of Engineering at Tufts and co-author of the study, said that “using the BioDome cap for the first 24 hours helps to mimic an amniotic fluid-like environment, which together with the right drugs allows the reconstruction process to continue without interference from scar tissue. “
The five chemicals each had very specific functions, including inhibiting collagen production (which leads to scarring), reducing inflammation, and stimulating the growth of nerves, blood vessels, and muscles. The cocktail was intended to prevent the frog’s immune system from shutting off the stump.
“It’s exciting to see that the drugs we chose helped create an almost complete limb,” said Nirosha Murugan, a research partner at the Allen Discovery Center in Tufts and first author of the paper.
The regrowth of an almost fully functional bone in many of the treated frogs was a hopeful result for the researchers. The new limbs had bones, nerves and several “toes” that grew from the ends of the limbs – even though the toes had no bones. The frogs could feel when the limb was brushed with a stiff fiber, and could use it to swim through the water.
“The fact that it only required a brief exposure to the substances to set in motion a months-long regeneration process suggests that frogs and perhaps other animals may have dormant regenerative abilities that can be triggered into action,” Murugan said.
“We will then test how this treatment can be applied to mammals,” said the corresponding author Michael Levin, director of the Allen Discovery Center at Tufts.
The research team hopes the study “brought us one step closer to the goal of regenerative medicine.” They then plan to test the treatment on mammals.