For the first time ever, scientists have identified the cells that enable lizards to regrow their tails. They hope to use this information to find a way to encourage the spinal cord in humans to regrow after damage and restore function.
Some lizards have the ability to drop their tails, known as autotomy, if threatened by predators. This defensive behavior is particularly common in lizards, but also found in some salamanders, with their tails continuing to wriggle to distract an attacker while the crafty animal makes a swift exit. Once this happens, the lizards will then start to regrow their tail. For geckos, this can happen within just 30 days, which is faster than any other lizard.
What is interesting for scientists – particularly those in the medical profession – is the fact that unlike mammals, the spinal cord of lizards extends down into the tail. This means that when the animals begin the process of regrowing their tail, they also have to regrow their spinal cord. By studying how these clever reptiles manage this impressive feat, they hope to inspire new treatments in humans.
“We knew the gecko's spinal cord could regenerate, but we didn't know which cells were playing a key role,” explains Professor Matthew Vickaryous, who led the new study published in the Journal of Comparative Neurology, in a statement. “Humans are notoriously bad at dealing with spinal cord injuries so I'm hoping we can use what we learn from geckos to coax human spinal cord injuries into repairing themselves.”
The researchers simulated a peckish predator in the lab by pinching the tails of leopard geckos and then analyzed in detail what is going on at a cellular level both before and after tail detachment. They found that the spinal cord contained a special type of stem cell called radial glia. These cells are found in all vertebrates studied to date, and usually help guide newborn neurons to their final destinations. Other than that, they tend to be fairly quiet overall.
But when a lizard's tail is severed, something else kicks in. “The cells make different proteins and begin proliferating more in response to the injury,” says Vickaryous. “Ultimately, they make a brand new spinal cord. Once the injury is healed and the spinal cord is restored, the cells return to a resting state.”
The lizards' regenerative ability is not only limited to their tails, as they can also repair other parts of their central nervous system. Because of this, the team now want to focus on how they manage to make new brain cells.