Scientists in the United States say they have made progress in repairing spinal cord injuries in paralysed rats.
Rats regained some bladder control after surgery to transplant nerve cells into the spinal cord, combined with injections of a cocktail of chemicals.
The study, published in the Journal of Neuroscience, could raise hopes for one day treating paralysed patients.
Complex surgery was carried out to transplant nerves from the rodents' ribs into the gap in the middle of their spinal cord.
The BBC reports a special "glue" was used that boosts cell growth together with a chemical that breaks down scar tissue in an attempt to encourage the nerve cells to regenerate and connect up.
The researchers found for the first time that injured nerve cells could re-grow for "remarkably long distances" (about 2cm).
While the rats did not regain the ability to walk, they did recover some bladder function.
"Although animals did not regain the ability to walk, they did recover a remarkable measure of urinary control," said lead author Dr Jerry Silver of Case Western Reserve Medical School, Cleveland, Ohio.
"This is the first time that significant bladder function has been restored via nerve regeneration after a devastating cord injury," added co-author Dr Yu-Shang Lee of the Cleveland Clinic, Ohio.
The BBC reports the findings may help future efforts to restore other functions lost after spinal cord injury.
They also raise hope that similar strategies could one day be used to restore bladder function in people with severe spinal cord injuries.
Dr Silver said further animal experiments will be needed to see if the technique could work in humans.