How geckos regrow their tails may help treat spinal injuries

In a first, scientists have discovered the cells that allow geckos to regenerate their tails, a finding that may pave the way for new therapies which can coax human spinal cord injuries to repair themselves.
Many lizards can detach a portion of their tail to avoid a predator and then regenerate a new one. Unlike mammals, the lizard tail includes a spinal cord.
Researchers found that the spinal cord of the tail contained a large number of stem cells - which are capable of growing into different types of cells - and proteins known to support their growth.
"We knew the gecko's spinal cord could regenerate, but we didn't know which cells were playing a key role," said Matthew Vickaryous, from University of Guelph in Canada.

"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," said Vickaryous, lead author of the study published in the Journal of Comparative Neurology.
Geckos are able to re-grow a new tail within 30 days - faster than any other type of lizard.

In the wild, they detach their tails when grabbed by a predator. The severed tail continues to wiggle, distracting the predator long enough for the reptile to escape.
In the lab, Vickaryous simulates this by pinching the gecko's tail causing the tail to drop. Once detached, the site of the tail loss begins to repair itself, eventually leading to new tissue formation and a new spinal cord.

Researchers investigated what happens at the cellular level before and after detachment.
They found that the spinal cord houses a special type of stem cell known as the radial glia. These stem cells are normally fairly quiet.
"But when the tail comes off everything temporarily changes. The cells make different proteins and begin proliferating more in response to the injury.
"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," said Vickaryous.
Humans, on the other hand, respond to a spinal cord injury by making scar tissue rather than new tissue, he added.

The scar tissue seals the wound quickly, but sealing the injury prevents regeneration.
"This may play a role in why we have a limited ability to repair our spinal cords. We are missing the key cells types required," Vickaryous said.