It is an extremely rare ability for an animal to be able to regrow a lost limb because joints are very complex structures. The reality is, lucky animals such as lizards and salamanders can regrow their lost appendages, but if we humans lose a limb we are left with a stump. In big efforts to turn our luck around, scientists have been looking for ways in which we too can gain this ability to regrow our limbs.
Over the years, studies have led researchers closer and closer to understanding the science behind the regeneration of body parts. Ken Muneoka at Texas A&M University and his colleagues got close when they were able to regenerate the bones in mice after they were amputated. They treated the stump with a bone-growing protein called BMP2 and the bone did grow back, but joint structures never formed. They had only figured out a piece of the puzzle.
Upon further research, the team realized that there was another bone-growing protein called BMP9 which they believed could be another piece of the puzzle, the piece essential to joint building. So next, they tried applying this BMP9 protein to mice that had their toes amputated. After just 3 days they saw amazing results. Over 60 per cent of the stump bones formed a layer of cartilage, as seen in joints, at the end of the bones.
Then, they combined what they had learned from both studies. They took mice with amputated toes and treated their wounds first with BMP2, and then BMP9 a week later. The results were even more effective! The bones regrew as well as formed more complete joint structures with part of the new bones attached to them. The research was published in the journal Nature Communications.
Muneoka is so optimistic about this discovery that he says:
“Our study is transformational.”
The method has not been successful in producing a full toe regrowth yet, but there is great potential in this process. Muneoka says this experiment proves that, even though mammals can’t regenerate body parts, they have cells that know how to and could potentially grow. He said, “they can do it, they just don’t do it. So, we have to figure out what’s constraining them.” He strongly believes that one day, we will be able to help amputees regrow their limbs, possibly using this pair of proteins.