Scientists Regrow Legs in Frogs, Giving Hope to Humans

Scientists have grown legs in frogs through a new drug treatment that successfully regenerated the leg of a frog. The treatment is a landmark for regenerative medicine that may pave the way for human applications.

Scientists tested the cocktail of drugs on an African clawed frog, a species that is incapable of regenerating its own limbs. The frog was administered the drugs over the course of 24 hours, after which an 18-month process of generation occurred. The frog eventually regrew an entirely functional leg. The researchers behind the study hope that this success may be the seed for an equivalent regenerative treatment for human patients.

“It’s exciting to see that the drugs we selected were helping to create an almost complete limb,” said Nirosha Murugan of Tufts University in Massachusetts, the first author of the study. “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.”

There are a wide variety of animals capable of naturally regenerating their limbs, mainly amphibians like salamanders and lizards, but creatures as diverse as starfish and crabs have similar restorative functions as well.

While human beings have the some partial ability to regenerate body parts — mostly internal organs like the liver, and thin organs like the skin — it is impossible to regenerate human limbs in a way that resembles the process of animals.

The primary block in human limb regeneration is the growth of scar tissue at the site of injury. While scar tissue helps the body fend off infection and blood loss, it seals off the site of the severance — for good.

Regenerative drug could potentially restore human limbs

The study uses a mixture of five drugs that are enclosed in a silicone cap affixed to the wound. Each drug targets a different aspect of the wound to stimulate regrowth. One drug halts collagen production in order to prevent scar tissue from growing. This could be the key for developing a regenerative drug for mammals, and, eventually, humans.

“Covering the open wound with a liquid environment under the (silicone cap), with the right drug cocktail, could provide the necessary first signals to set the regenerative process in motion,” said Michael Levin, the director of the Allen Discovery Center at Tufts.

Bob Lanza, an expert in regenerative medicine who did not participate in the research, said that the results were an “amazing achievement.”

“The study has extremely exciting ramifications for regenerative medicine,” he said. “Although frogs have much greater regenerative capacity than humans, this is a very important first step. With the right combination of drugs and factors, a similar approach could potentially spur regeneration and restore lost function in humans.”