Jeff Marquis and Kelly Thomas, fellow research participants and spinal cord injury patients, in a rehab session.
Seven years ago, mountain biking near his home in Whitefish, Montana, Jeff Marquis felt confident enough to try for a jump he usually avoided. But he hesitated just a bit as he was going over. Instead of catching air, Marquis crashed.
Researchers' major new insight is that recovery is still possible, even years after an injury.
After 18 days on a ventilator in intensive care and two-and-a-half months in a rehabilitation hospital, Marquis was able to move his arms and wrists, but not his fingers or anything below his chest. Still, he was determined to remain as independent as possible. "I wasn't real interested in having people take care of me," says Marquis, now 35. So, he dedicated the energy he formerly spent biking, kayaking, and snowboarding toward recovering his own mobility.
For generations, those like Marquis with severe spinal cord injuries dreamt of standing and walking again – with no realistic hope of achieving these dreams. But now, a handful of people with such injuries, including Marquis, have stood on their own and begun to learn to take steps again. "I'm always trying to improve the situation but I'm happy with where I'm at," Marquis says.
The recovery Marquis and a few of his fellow patients have achieved proves that our decades-old understanding of the spinal cord was wrong. Researchers' major new insight is that recovery is still possible, even years after an injury. Only a few thousand nerve cells actually die when the spinal cord is injured. The other neurons still have the ability to generate signals and movement on their own, says Susan Harkema, co-principal investigator at the Kentucky Spinal Cord Injury Research Center, where Marquis is being treated.
"The spinal cord has much more responsibility for executing movement than we thought before," Harkema says. "Successful movement can happen without those connections from the brain." Nerve cell circuits remaining after the injury can control movement, she says, but leaving people sitting in a wheelchair doesn't activate those sensory circuits. "When you sit down, you lose all the sensory information. The whole circuitry starts discombobulating."
Harkema and others use a two-pronged approach – both physical rehabilitation and electrical stimulation – to get those spinal cord circuits back into a functioning state. Several research groups are still honing this approach, but a few patients have already taken steps under their own power, and others, like Marquis, can now stand unassisted – both of which were merely fantasies for spinal cord injury patients just five years ago.
"This really does represent a leap forward in terms of how we think about the capacity of the spinal cord to be repaired after injury," says Susan Howley, executive vice president for research for the Christopher & Dana Reeve Foundation, which supports research for spinal cord injuries.
Jeff Marquis biking on a rock before his accident.
This new biological understanding suggests the need for a wholesale change in how people are treated after a spinal cord injury, Howley says. But today, most insurance companies cover just 30-40 outpatient rehabilitation sessions per year, whether you've sprained your ankle or severed your spinal cord. To deliver the kind of therapy that really makes a difference for spinal cord injury patients requires "60-80-90 or 150 sessions," she says, adding that she thinks insurance companies will more than make up for the cost of those therapy sessions if spinal cord injury patients are healthier. Early evidence suggests that getting people back on their feet helps prevent medical problems common among paralyzed people, including urinary tract infections, which can require costly hospital stays.
"Exercise and the ability to fully bear one's own weight are as crucial for people who live with paralysis as they are for able-bodied people," Howley notes, adding that the Reeve Foundation is now trying to expand the network of facilities available in local communities to offer this essential rehabilitation.
"Providing the right kind of training every day to people could really improve their opportunity to recover," Harkema says.
It's not entirely clear yet how far someone could progress with rehabilitation alone, Harkema says, but probably the best results for someone with a severe injury will also require so-called epidural electrical stimulation. This device, implanted in the lower back for a cost of about $30,000, sends an electrical current at varying frequencies and intensities to the spinal cord. Several separate teams of researchers have now shown that epidural stimulation can help restore sensation and movement to people who have been paralyzed for years.
Epidural stimulation boosts the electrical signal that is generated below the point of injury, says Daniel Lu, an associate professor and vice chair of neurosurgery at the UCLA School of Medicine. Before a spinal cord injury, he says, a neuron might send a message at a volume of 10 but after injury, that volume might drop to a two or three. The epidural stimulation potentially trains the neuron to respond to the lower volume, Lu says.
Lu has used such stimulators to improve hand function – "essentially what defines us" – in two patients with spinal cord injuries. Both increased their grip strength so they now can lift a cup to drink by themselves, which they couldn't do before. He's also used non-invasive stimulation to help restore bladder function, which he says many spinal cord injury patients care about as much as walking again.
Not everyone will benefit from these treatments. People whose injury was caused by a cut to the spinal cord, as with a knife or bullet, probably can't be helped, Lu says, adding that they account for less than 5 percent of spinal cord injuries.
The current challenge Lu says is not how to stimulate the spinal cord, but where to stimulate it and the frequency of stimulation that will be most effective for each patient. Right now, doctors use an off-the-shelf stimulator that is used to treat pain and is not optimized for spinal cord patients, Harkema says.
Swiss researchers have shown impressive results from intermittent rather than continuous epidural stimulation. These pulses better reflect the way the brain sends its messages, according to Gregoire Courtine, the senior author on a pair of papers published Nov. 1 in Nature and Nature Neuroscience. He showed that he could get people up and moving within just a few days of turning on the stimulation. Three of his patients are walking again with only a walker or minimal assistance, and they also gained voluntary leg movements even when the stimulator was off. Continuous stimulation, this research shows, actually interferes with the patients' perception of limb position, and thus makes it harder for them to relearn to walk.
Even short of walking, proper physical rehabilitation and electrical stimulation can transform the quality of life of people with spinal cord injury, Howley and Harkema say. Patients don't need to be able to reach the top shelf or run a marathon to feel like they've been "cured" from their paralysis. Instead, recovering bowel, bladder and sexual functions, the ability to regulate their temperature and blood pressure, and reducing the breakdown of skin that can lead to a life-threatening infection can all be transformative – and all appear to improve with the combination of rehabilitation and electrical stimulation.
Howley cites a video of one of Harkema's patients, Stefanie Putnam, who was passing out five to six times a day because her blood pressure was so low. She couldn't be left alone, which meant she had no independence. After several months of rehabilitation and stimulation, she can now sit up for long periods, be left alone, and even, she says gleefully, cook her own dinner. "Every time I watch it, it brings me to tears," Howley says of the video. "She's able to resume her normal life activity. It's mind-boggling."
The work also suggests a transformation in the care of people immediately after injury. They should be allowed to stand and start taking steps as soon as possible, even if they cannot do it under their own power, Harkema says. Research is also likely to show that quickly implanting a stimulator after an injury will make a difference, she says.
There may be medications that can help immediately after an injury, too. One drug currently being studied, called riluzole, has already been approved for ALS and might help limit the damage of a spinal cord injury, Howley says. But testing its effectiveness has been a slow process, she says, because it needs to be given within 12 hours of the initial injury and not enough people get to the testing sites in time.
Stem cell therapy also offers promise for spinal cord injury patients, Howley says – but not the treatments currently provided by commercial stem cell clinics both in the U.S. and overseas, which she says are a sham. Instead, she is carefully following research by a California-based company called Asterias Biotherapeutics, which announced plans Nov. 8 to merge with a company called BioTime.
Asterias and a predecessor company have been treating people since 2010 in an effort to regrow nerves in the spinal cord. All those treated have safely tolerated the cells, but not everyone has seen a huge improvement, says Edward Wirth, who has led the trial work and is Asterias' chief medical director. He says he thinks he knows what's held back those who didn't improve much, and hopes to address those issues in the next 3- to 4-year-long trial, which he's now discussing with the U.S. Food and Drug Administration.
So far, he says, some patients have had an almost complete return of movement in their hands and arms, but little improvement in their legs. The stem cells seem to stimulate tissue repair and regeneration, he says, but only around the level of the injury in the spinal cord and a bit below. The legs, he says, are too far away to benefit.
Wirth says he thinks a combination of treatments – stem cells, electrical stimulation, rehabilitation, and improved care immediately after an injury – will likely produce the best results.
While there's still a long way to go to scale these advances to help the majority of the 300,000 spinal cord injury patients in the U.S., they now have something that's long been elusive: hope.
"Two or three decades ago there was no hope at all," Howley says. "We've come a long way."
In a recent research trial, patients with Parkinson's disease reported that their symptoms had improved after stem cells were implanted into their brains. Martin Taylor, far right, was diagnosed at age 32.
For years, there's been little improvement in the standard treatment. Patients are typically given the drug levodopa, a chemical that's absorbed by the brain’s nerve cells, or neurons, and converted into dopamine. This drug addresses the symptoms but has no impact on the course of the disease as patients continue to lose dopamine producing neurons. Eventually, the treatment stops working effectively.
BlueRock Therapeutics, a cell therapy company based in Massachusetts, is taking a different approach by focusing on the use of stem cells, which can divide into and generate new specialized cells. The company makes the dopamine-producing cells that patients have lost and inserts these cells into patients' brains. “We have a disease with a high unmet need,” says Ahmed Enayetallah, the senior vice president and head of development at BlueRock. “We know [which] cells…are lost to the disease, and we can make them. So it really came together to use stem cells in Parkinson's.”
In a phase 1 research trial announced late last month, patients reported that their symptoms had improved after a year of treatment. Brain scans also showed an increased number of neurons generating dopamine in patients’ brains.
Increases in dopamine signals
The recent phase 1 trial focused on deploying BlueRock’s cell therapy, called bemdaneprocel, to treat 12 patients suffering from Parkinson’s. The team developed the new nerve cells and implanted them into specific locations on each side of the patient's brain through two small holes in the skull made by a neurosurgeon. “We implant cells into the places in the brain where we think they have the potential to reform the neural networks that are lost to Parkinson's disease,” Enayetallah says. The goal is to restore motor function to patients over the long-term.
Five patients were given a relatively low dose of cells while seven got higher doses. Specialized brain scans showed evidence that the transplanted cells had survived, increasing the overall number of dopamine producing cells. The team compared the baseline number of these cells before surgery to the levels one year later. “The scans tell us there is evidence of increased dopamine signals in the part of the brain affected by Parkinson's,” Enayetallah says. “Normally you’d expect the signal to go down in untreated Parkinson’s patients.”
"I think it has a real chance to reverse motor symptoms, essentially replacing a missing part," says Tilo Kunath, a professor of regenerative neurobiology at the University of Edinburgh.
The team also asked patients to use a specific type of home diary to log the times when symptoms were well controlled and when they prevented normal activity. After a year of treatment, patients taking the higher dose reported symptoms were under control for an average of 2.16 hours per day above their baselines. At the smaller dose, these improvements were significantly lower, 0.72 hours per day. The higher-dose patients reported a corresponding decrease in the amount of time when symptoms were uncontrolled, by an average of 1.91 hours, compared to 0.75 hours for the lower dose. The trial was safe, and patients tolerated the year of immunosuppression needed to make sure their bodies could handle the foreign cells.
Claire Bale, the associate director of research at Parkinson's U.K., sees the promise of BlueRock's approach, while noting the need for more research on a possible placebo effect. The trial participants knew they were getting the active treatment, and placebo effects are known to be a potential factor in Parkinson’s research. Even so, “The results indicate that this therapy produces improvements in symptoms for Parkinson's, which is very encouraging,” Bale says.
Tilo Kunath, a professor of regenerative neurobiology at the University of Edinburgh, also finds the results intriguing. “I think it's excellent,” he says. “I think it has a real chance to reverse motor symptoms, essentially replacing a missing part.” However, it could take time for this therapy to become widely available, Kunath says, and patients in the late stages of the disease may not benefit as much. “Data from cell transplantation with fetal tissue in the 1980s and 90s show that cells did not survive well and release dopamine in these [late-stage] patients.”
Searching for the right approach
There's a long history of using cell therapy as a treatment for Parkinson's. About four decades ago, scientists at the University of Lund in Sweden developed a method in which they transferred parts of fetal brain tissue to patients with Parkinson's so that their nerve cells would produce dopamine. Many benefited, and some were able to stop their medication. However, the use of fetal tissue was highly controversial at that time, and the tissues were difficult to obtain. Later trials in the U.S. showed that people benefited only if a significant amount of the tissue was used, and several patients experienced side effects. Eventually, the work lost momentum.
“Like many in the community, I'm aware of the long history of cell therapy,” says Taylor, the patient living with Parkinson's. “They've long had that cure over the horizon.”
In 2000, Lorenz Studer led a team at the Memorial Sloan Kettering Centre, in New York, to find the chemical signals needed to get stem cells to differentiate into cells that release dopamine. Back then, the team managed to make cells that produced some dopamine, but they led to only limited improvements in animals. About a decade later, in 2011, Studer and his team found the specific signals needed to guide embryonic cells to become the right kind of dopamine producing cells. Their experiments in mice, rats and monkeys showed that their implanted cells had a significant impact, restoring lost movement.
Studer then co-founded BlueRock Therapeutics in 2016. Forming the most effective stem cells has been one of the biggest challenges, says Enayetallah, the BlueRock VP. “It's taken a lot of effort and investment to manufacture and make the cells at the right scale under the right conditions.” The team is now using cells that were first isolated in 1998 at the University of Wisconsin, a major advantage because they’re available in a virtually unlimited supply.
Other efforts underway
In the past several years, University of Lund researchers have begun to collaborate with the University of Cambridge on a project to use embryonic stem cells, similar to BlueRock’s approach. They began clinical trials this year.
A company in Japan called Sumitomo is using a different strategy; instead of stem cells from embryos, they’re reprogramming adults' blood or skin cells into induced pluripotent stem cells - meaning they can turn into any cell type - and then directing them into dopamine producing neurons. Although Sumitomo started clinical trials earlier than BlueRock, they haven’t yet revealed any results.
“It's a rapidly evolving field,” says Emma Lane, a pharmacologist at the University of Cardiff who researches clinical interventions for Parkinson’s. “But BlueRock’s trial is the first full phase 1 trial to report such positive findings with stem cell based therapies.” The company’s upcoming phase 2 research will be critical to show how effectively the therapy can improve disease symptoms, she added.
The cure over the horizon
BlueRock will continue to look at data from patients in the phase 1 trial to monitor the treatment’s effects over a two-year period. Meanwhile, the team is planning the phase 2 trial with more participants, including a placebo group.
For patients with Parkinson’s like Martin Taylor, the therapy offers some hope, though Taylor recognizes that more research is needed.
BlueRock Therapeutics
“Like many in the community, I'm aware of the long history of cell therapy,” he says. “They've long had that cure over the horizon.” His expectations are somewhat guarded, he says, but, “it's certainly positive to see…movement in the field again.”
"If we can demonstrate what we’re seeing today in a more robust study, that would be great,” Enayetallah says. “At the end of the day, we want to address that unmet need in a field that's been waiting for a long time.”
Editor's note: The company featured in this piece, BlueRock Therapeutics, is a portfolio company of Leaps by Bayer, which is a sponsor of Leaps.org. BlueRock was acquired by Bayer Pharmaceuticals in 2019. Leaps by Bayer and other sponsors have never exerted influence over Leaps.org content or contributors.