The ability to urinate normally is something that paralysed people often say would improve their lives. New work offers some hope.

When the spinal cord is severed, the brain can no longer control muscles below the break, which affects bladder control. Grafting nerve tissue onto the injured spinal cord so that new neurons from the brainstem can grow over the gap could help to reverse this, but scar tissue gets in the way.

About a decade ago, researchers discovered that a bacterial enzyme called chondroitinase breaks down this kind of scar tissue. To test how this enzyme might help a graft regrow, Jerry Silver of Case Western Reserve University’s School of Medicine in Cleveland, Ohio, and colleagues performed surgery on rats whose spinal cords had been completely severed. The researchers removed a section of nerve from another part of each rat’s body, such as the leg, and used it to form a graft over the damaged spinal cord. They added chondroitinase to the area, along with a signalling molecule called FGF that helped the grafts align correctly.

Pressure’s on

Six months later, the rats still could not walk but they were able to pee unaided. The pressure in their bladders indicated that they had regained roughly two-thirds of their bladder function. The team found that nerves from the brainstem had regrown across the break and were transmitting signals to the muscles that control the bladder.


It seems some brainstem neurons can grow down the spinal cord if helped through scar tissue, says Silver. “That’s really cool, I was shocked.” He says he suspects that humans have a similar set of super-regenerating cells.

Before the technique could be tried in humans, however, it will have to be trialled in larger animals such as cats, says John Houle of Drexel University in Philadelphia, Pennsylvania. Additionally, Silver and his colleagues still have to establish whether the technique can repair spinal cords that were injured long before the graft surgery, which may be less able to grow back.

The good news is that both chondroitinase and nerve grafts have been used safely in humans before.

Journal reference: Journal of Neuroscience, DOI: 10.1523/jneurosci.1116-12.2013