Nerve cells extracted from a patient's own nose could one day be used to cure paralysis. At least, that is the hope of neuroscientists in Australia who have announced the beginning of tests on people.
The team, led by Alan Mackay-Sim of Griffith University in Brisbane, has recruited three people who have been paralysed from the waist down for between six months and three years, and plans to enlist another five. Half the patients will receive a spinal injection of the nasal cells.
The cells, called olfactory ensheathing cells, connect the lining of the nose with the brain, giving us our sense of smell. Unlike most nerve cells, they continue to regenerate throughout life, a property that probably evolved because they can be destroyed by infections. "There's only a few microns of mucus between the air and the nerve endings," points out Mackay-Sim.
The idea is that the transplanted cells will provide a bridge to allow spinal nerves to grow through the damaged area. "The evidence so far suggests that olfactory ensheathing cells are going to be the front runners for the bridging effect," says neuroscientist Robin Franklin of the University of Cambridge.
Skull surgery
Several groups worldwide have done experiments with ensheathing cells in rats, some of which have been highly successful. For instance, animals with totally severed spinal cords have regained control of their hind legs after receiving transplants of the cells.
But in rats, the cells have usually been removed from inside the skull, making the procedure unsuitable for people. A second obstacle has been that not enough cells could be collected from a single individual to patch up a human spinal cord.
Mackay-Sim's team has solved those problems by developing a method of removing the cells under a local anaesthetic and growing them in culture to produce larger numbers.
Battery of tests
Each patient in the trial will undergo a battery of tests to see if there is any improvement in their condition. "Even if people could get back some sensation around their bottom and legs, that would be extremely helpful in preventing bedsores. A step up would be an improvement in bladder or bowel or sexual function," says team member Tim Geraghty, director of the Spinal Injuries Unit of Princess Alexandra Hospital in Brisbane.
Injecting ensheathing cells is just one approach to curing paralysis. Others include transplanting so-called Schwann cells from peripheral nerves, using growth factors to stimulate nerve growth, and boosting the immune system in the damaged area (New Scientist magazine, 14 August 1999, p 36).
And progress has recently been made towards using stem cells to repair spines. An effective treatment will probably combine several different approaches, Franklin says.