Scientists regrow frog’s legs in a breakthrough experiment. Will humans be next?

By Mariusz Bogacki, Researcher and Science Communicator, Edinburgh

Unlike lizards or salamanders, frogs couldn’t regenerate complex body parts like arms or legs – until now!

Only a few animals in the world are able to regrow their own limbs. Salamanders, lizards, crabs and starfish are the most well-known examples. They can do so thanks to blastema cells, which allow for almost instant mass formation of stem cells at the end of stump, after the limb is lost.

Frogs, just like humans and most mammals, have very limited regenerative abilities. For example, we can regrow tissue to close a wound to protect our bodies from blood loss and infection. This would suggest that our bodies have some innate knowledge on how to regenerate bodily parts.

There is, of course, a big difference between tissue regrowth and bone structure reproduction, but the question is whether we can artificially stimulate the growth of limbs in our bodies. A team of researchers from Harvard and Tufts University just proved that the answer to this question is yes!

The scientists developed a specific multidrug, pro-regenerative treatment and applied it to African clawed frogs with amputated legs. Each of the used drugs had a different role, including easing inflammation, stopping collagen production to avoid scarring, and encouraging the growth of nerve fibbers, blood vessels, and muscle. The drugs were put into gel in a wearable dome called a BioDome. The dome was then sealed over the frog's stump for 24 hours. The regeneration process began after the removal of the BioDome.

Over the course of the next 18 months, the frogs slowly regrew their legs, which had a bone structure, internal tissue, including neurons, and 'toes', all of which were similar to the frogs’ original legs. Even though the legs did not regrow impeccably – for example, there were no bones in the toes – the frogs were able to use them in swimming and moving.

One of the most interesting findings from the research is that a short exposure to the drug treatment caused a long and complex process of regeneration. This suggest that perhaps other animals may have dormant regenerative capabilities that can be triggered into action.

This is the next challenge and frontier in the field of developmental and regenerative biology. In the United States alone, it is estimated that by 2050 up to 3,6 million people per year will be affected by some form of limb loss. This group includes diabetics, veterans or war or trauma survivors among others. Technological developments in the field of advanced prosthetics still only offer limited solutions. Here’s to hoping that one day humans could become more like lizards and starfish!