Paralyzed rats could walk again after scientists in Switzerland treated their injured spinal cords through a combination of chemical, electrical and physical stimulation.
Gregoire Courtine, the study's lead author, said the technique would not completely cure a spinal cord injury, but the study gave scientists an idea of how they could combine therapies, each of which have been or are being tested in humans.
"This kind of approach will not make miracles," said Gregoire Courtine, the study's lead author, "but it's interesting because it offers new therapeutic avenues for these very traumatic injuries."
First, the researchers injected the injured rats with chemicals designed to mimic the body's own cocktail of signals that coordinate movement of the lower body. Five to 10 minutes after the injection, the researchers sent electrical impulses to tiny electrodes placed in the narrow space between the bones of the spine and the nerves of the spinal cord, stoking the spinal cord's ability to come back after an injury, a quality scientists call neuroplasticity.
The findings were published today in the journal Science.
After a few weeks of the combination of chemicals and electricity, 10 rats were trained to use their paralyzed hind legs with the help of a robotic device for 30 minutes each day, until they could move their legs voluntarily.
After a few weeks of treatment, the rats are not only voluntarily initiated a walking gait but soon sprinted, climbed stairs and avoided obstacles, the study found.
The improvement to the spinal cord was visible, too. The rats' spinal cords regrew nerves to bridge the gap of their injuries.
The chemical, electrical and physical training therapies have each been individually studied in paralyzed humans. In 2011, electrical stimulation of the spine helped Rob Summers, a paralyzed 25-year-old, move his legs voluntarily.
Neurologists are cautiously encouraged by the results of the study, but many say much more research would be needed before the techniques can be tested in paralyzed humans.
Peter Gorman, chief of rehabilitation medicine at the Kernan Orthopedics and Rehabilitation Hospital, said because spinal cord injuries are complex, using a combination of the therapies to overcome them makes sense.
"It is, however, premature to say that this can be directly applied to people, but it is certainly getting closer," Gorman said.
Gorman noted that spinal cord injuries in humans are typically much more complicated than the neat cuts the researchers made to the rats' spines.
Courtine said it is too early to know whether the approach will work in humans who have spinal cord injuries, and if it does, it is unlikely that a person would completely recover the ability to walk without help.
"But this condition is so traumatic that even a very small improvement would be a major step forward for these patients," he said.
ABC News' Dr. Murtaza Akhter contributed to this report.