Scientists Successfully Regrow a Frog’s Leg – Are Human Limbs Next?

In a major scientific step forward, scientists were able to regrow the amputated leg of a frog. With a mixture of different drugs, scientists in the United States triggered the regrowth of a leg in a species of African clawed frog named Xenopus laevis. This was a very important step forward as they said that it is a “step closer to the goal of regenerative medicine.”

The team of experts, which were based at Harvard University's Wyss Institute and Tufts University, added a mixture of five drugs to the amputated area of the frog’s leg and left it there for 24 hours. Amazingly, after 18 months, the newly regrown leg was nearly completely functional. In fact, the frog was able to swim in the water and even reacted to being touched. Additionally, several of its toes regrew, but they weren’t webbed.

Since the limb grew back in months, it may indicate that frogs and possibly other animals have regenerative capabilities that lie dormant but can be awakened with treatments. “I think the way to really achieve regenerative medicine is to exploit the collective intelligence of the body's cells. They already know how to build all of these organs. They did it during embryonic development. All that information is still there,” explained Mike Levin who is a Vannevar Bush Professor of Biology and director of the Allen Discovery Center at Tufts. “For me, the goal is to identify triggers, very simple kinds of stimuli, that will kick-start the cells and convince them to build whatever it is that you want them to build.”

James Monaghan, who is an associate professor in the department of biology at Northeastern University, described the results as being “impressive” and “exciting”. “Xenopus frogs are somewhere in between a salamander that regrows a limb nearly perfectly and a mammal that generates a scar after amputation. Adult Xenopus frogs regenerate a spike after amputation, but the spike lacks any pattern like a limb,” he explained, adding, “This study is significant because it shows that patterning, albeit not perfect, can be induced in a limb that typically regenerates only a spike.” (Pictures of the frog’s regrowth process of its leg can be seen here.)

As for what this means for humans regrowing their limbs, Monaghan stated, “An immediate translation of this strategy to humans is unlikely because a regenerative spike does not occur in humans as it does in Xenopus frogs. Yet, this work is exciting because it shows that endogenous regenerative processes can be enhanced by a short application of a drug cocktail.”

It is, however, an important step forward in scientists hopefully eventually being able to regrow human limbs. “Will we one day be able to regenerate a human digit or even a limb? Probably, but how long we need to wait is impossible to predict,” noted Ashley Seifert who is an associate professor of biology at the University of Kentucky who studies animal regeneration but wasn’t involved with the study.

The research was published in the journal Science Advances.