In more than 20 animals, the team had "almost 100 percent success of transplant," says Smith. "They survived and promoted growth from the host in a stunning way." Additionally, although the nerve tissue was not their own, the rats' bodies accepted the transplants without the use of an immunosuppressant. The team now plans to test the procedure in larger animals.

The axons must grow quickly, before the part of the severed nerve detached from the neuron dies. "We actually grow [axons] faster than what is thought possible," says Smith, noting that they can grow axons at a rate of up to a centimeter per day, while previously axons in dishes grow about 1 millimeter per day.

"What I like about this is that it takes a different approach than the standard biological approaches," says Jennifer Elisseeff, an assistant professor of biomedical engineering at Johns Hopkins University. She adds that a major obstacle to nerve regeneration is getting the nerves to grow fast enough. "This would be a more efficient way of inducing regeneration," she says. "This really accelerates it."

"This is a very interesting approach that demonstrates how bioengineering and cell therapy approaches can be combined to solve an important medical problem," says Ali Khademhosseini, an assistant professor at Harvard University who works on tissue engineering. "The bridging of the severed spine by using the process that has been described is highly promising." He adds that researchers still need to achieve results in primates and humans, as well as to demonstrate the technique's effectiveness in treating different nerve injuries.