The gecko's remarkable ability to regenerate its tail in the space of a month could help scientists figure out how to heal spine injuries in humans, and it's all down to the regenerative ability of stem cells.
Scientists studying gecko tails at the cellular level – how they detach when under pressure, and how they grow back again – have found a particular group of stem cells known as radial glial cells are responsible for growing the tail back.
As gecko tails hold much of their spinal cord, the team from the University of Guelph in Canada thinks that studying these radial glial cells and their behaviour could give us a better understanding of how spinal cords could eventually be prompted to grow back in human bodies.
"To many scientists, [geckos] are the ultimate forms of regenerating species," one of the researchers, Matthew Vickaryous, told Claire Maldarelli at Popular Science.
The study looked at tail regeneration in leopard geckos, which surrender their tails relatively easily when faced with a predator – the researchers could literally pinch the tails to get them to fall away.
When that happens, the radial glial cells start multiplying and generating a variety of proteins to respond to the injury. Like other stem cells, they can morph into different types of cells depending on what the body needs.
In fact, there's already been promising research looking at how stem cells could be coaxed into regenerating parts of the spinal cord in mammals.
The researchers also noticed a blood clot forming when the gecko's tail was detached, sealing the injury. By blocking that clot with a piece of skin, the tail regeneration process was stopped.
That suggests there's something about the open wound that passes the right signals back to the gecko that the tail needs replacing. It's possible that the scar tissue that forms around spinal injuries in humans works like the skin placed on the gecko tails, somehow preventing regrowth.
The scar tissue that human bodies produce is important in reducing inflammation, but the gecko seems to do fine without it, leaving the researchers to wonder if this could be a clue as to how they can regenerate extra limbs so quickly.
"This absence of a scar is a big feature, we think, that permits them to regrow," Vickaryous told Popular Science.
The next question is why the human body forms scar tissue rather than growing new cells. Humans have plenty of radial glial cells as developing foetuses, but these disappear as the body develops, so replacing them could be one future option for treatment.
We're still a long way from translating these findings into something that might work for spinal cord injuries, but it's another step towards that goal, like the research from earlier this year looking at reconnecting sensory neurons in the spine.
What's more, we've also seen recent research into manipulating wound healing so that scar tissue doesn't form – by changing the protein signalling in lab tests, the researchers were able to regenerate normal skin.
If we can eventually figure out a way to prompt stem cells in the spine into regrowing the right kind of tissue, we might have the gecko to thank.
"As the closest living regeneration-competent relatives of mammals, reptiles such as geckos provide novel opportunities to probe the mechanisms leading to successful functional recovery following spinal cord injury," conclude the researchers.
The research has been published in the Journal of Comparative Neurology.