Paralyzed Rats Learn to Walk: For Humans, New Hope or Old Hype?

While regaining the ability to walk may not be the first priority for those with a spinal-cord injury (SCI), recent advances in research indicate that reversing paralysis—at least when it comes to getting out of the wheelchair—may be closer than ever before.

A study published this week in the journal Nature Neuroscience shows that scientists were able to restore motor function to rats with severed spinal cords thanks to a combination of pharmacological agents and electrodes implanted under the skin to stimulate the spinal cord. By putting the rats on a treadmill to create weight-bearing triggers in the brain, these elements are able to stimulate movement in the legs that is both controlled and strategic. "If the treadmill is stopped, they will not step. If you start the treadmill, they will start to step. If you turn them to the side on the treadmill, they will step sideways," says Reggie Edgerton, a professor of neurobiology at the David Geffen School of Medicine at UCLA.

Of course, this isn't the first time paralyzed rats have learned to walk again. In 2006, scientists were able to create similar effects through stem-cell therapy, a finding that garnered national attention thanks to a positive report on 60 Minutes. But since that time, the research has not advanced to human trials. "People have been talking to me about the rats on 60 Minutes for years," says Bob Smith, a quadriplegic from Hamilton Township, Mich. "Everyone is getting tired of hearing that in three to five years, we'll have human trials." Especially, he notes, when spinal-cord patients have been told the same thing for over a decade.

The new finding, however, might be tested in humans as soon as this year, says Edgerton. Moreover, since many SCI patients already have the electrodes implanted (they're used to help alleviate pain and control the spastic movements that can accompany a spinal-cord injury), and since the drugs used as part of the therapy are widely available, the logistics of finding suitable candidates and setting up the trials should move quickly.

A confluence of events may make the coming years a prime time for notable advancements in the treatment of those with spinal-cord injuries. "In the 80s, a couple of very seminal discoveries suggested that if you change the environment in the adult spinal cord, you could promote repair," says Susan Howley, the executive vice president of research at the Christopher and Dana Reeve Foundation. These discoveries set of a new wave of research, the results of which are just now advancing to human studies. In the '90s, the studies were bolstered by an influx of resources after Christopher Reeve was injured. "For the first time, a public face of spinal-cord injuries emerged. Money began to flow, awareness was raised, really good scientists began to flock to the field," says Howley. That the Obama administration has relaxed regulations on stem-cell research seems to promise even more advances: this week the National Institutes of Health announced it was expanding federal funding for stem-cell research.

At the same time, the Internet has helped organize spinal-cord patients and make their concerns— which often have to do with quality of life rather than learning to walk again—clear to researchers. (For instance: the inability to regulate one's own body temperature. SCI patients often can't sweat below the site of their injury and will overheat or pass out, making enjoying a warm day at the beach difficult.) "The researchers who sat down with spinal-cord-injury patients have said, 'For us to look at you, visually, we always think of walking as what you want.' But in reality, people don't realize that every other function in the body is affected by paralysis," says Smith.

The therapy described in Nature Neuroscience effects only with locomotion, and does not stimulate any of the nerves related to sweating, bladder control, or sexual function, for instance. Still, Edgerton notes the added health benefits to walking. "There's actually good evidence to suspect that when one loses their ability to bear weight and walk at some minimum amount of time each day, there's a lot of secondary changes that occur in one's physiology" that can negatively affect one's health, he says. Increased blood flow in the legs, for example, leads to a reduced risk of clots and allows wounds to heal faster.

Smith concurs. In 2004, he participated in a controversial fetal-cell-transplant surgery in China that helped restore some of his nerve function and allowed him to walk during physical therapy. "Strength between my shoulders and the top of the legs increased dramatically," says Smith of his walking therapy. "It helped with breathing and lung capacity ... I used to have a lot of problems just clearing my throat. Now I can scream as good as anybody."

While Egderton agrees that more research needs to be done to address quality-of-life issues in those with spinal-cord injuries, he's pleased by the study's results and it's implications for walking. "There's the concept of false hope, and so while I don't want to be too enthusiastic, I must admit I'm optimistic," he says.

Smith, who notes that promising research is often only as good as the funding available, sounds a similar tone. "We're optimistic," he says of the SCI community. "But we're cautiously optimistic."