Stem cells bring back feeling for paralysed patients

For the first time, people with broken spines have recovered feeling in previously paralysed areas after receiving injections of neural stem cells.

Three people with paralysis received injections of 20 million neural stem cells directly into the injured region of their spinal cord. The cells, acquired from donated fetal brain tissue, were injected between four and eight months after the injuries happened. The patients also received a temporary course of immunosuppressive drugs to limit rejection of the cells.

None of the three felt any sensation below their nipples before the treatment. Six months after therapy, two of them had sensations of touch and heat between their chest and belly button. The third patient has not seen any change.

"The fact we've seen responses to light touch, heat and electrical impulses so far down in two of the patients is very unexpected," says Stephen Huhn of StemCells, the company in Newark, California, developing and testing the treatment. "They're really close to normal in those areas now in their sensitivity," he adds.

"We are very intrigued to see that patients have gained considerable sensory function," says Armin Curt of Balgrist University Hospital in Zurich, Switzerland, where the patients were treated, and principal investigator in the trial.

The data are preliminary, but "these sensory changes suggest that the cells may be positively impacting recovery", says Curt, who presented the results today in London at the annual meeting of the International Spinal Cord Society.

Persistent gains

The patients are the first three of 12 who will eventually receive the therapy. The remaining recipients will have less extensive paralysis.

"The sensory gains, first detected at three months post-transplant, have now persisted and evolved at six months after transplantation," says Huhn. "We clearly need to collect much more data to demonstrate efficacy, but our results so far provide a strong rationale to persevere with the clinical development of our stem cells for spinal injury," he says.

"We need to keep monitoring these patients to see if feeling continues to affect lower segments of their bodies," says Huhn. "These are results after only six months, and we will follow these patients for many years."

Huhn says that the company has "compelling data" from animal studies that the donated cells can repair nerves within broken spines (Neurological Research, DOI: 10.1179/016164106X115116).

There could be several reasons why the stem cells improve sensitivity, says Huhn. They might help to restore myelin insulation to damaged nerves, improving the communication of signals to and from the brain. Or they could be enhancing the function of existing nerves, replacing them entirely or reducing the inflammation that hampers repair.

Abandoned trial

The announcement comes almost a year after the world's only other trial to test stem cells for spinal injury was suspended. Geron of Menlo Park, California, had injected neural stem cells derived from embryonic stem cells into four people with spinal injuries when it announced that it was going to focus on cancer therapies instead. The company also abandoned its other stem-cell programmes combating diabetes, heart disease and arthritis.

Huhn hopes that the results from the StemCells trial will revive the enthusiasm that evaporated following Geron's bombshell. "It's the first time we've seen a signal of some beneficial effect, so we're moving in the right direction, and towards a proof of concept," he says.

The news was welcomed by other pioneers of neural stem-cell research. "It looks encouraging and has some parallels with what we've seen in our trial in stroke patients," says Michael Hunt, CEO of ReNeuron, in Guildford, UK, which in 2010 became the first company in the world to treat strokes with stem cells.

"They appear to be making progress, and that's good for the stem-cell field generally, and for neural stem-cell research in particular," says Hunt. He says that seven people who have had strokes have now been treated, and that some have shown signs of functional improvement without adverse effects.

"It's early days, and we are proceeding cautiously before hopefully moving to more substantive trials," says Hunt.

"These initial data certainly indicate that stem-cell transplantation may help remediate some of the severe functional loss associated with spinal cord injury," says George Bittner of the University of Texas at Austin, who has developed a polymer-based system for rapid treatment of damaged nerves.

But, he says, a single mode of treatment is unlikely to be enough to restore function after spinal cord injuries. We will need "combinations of approaches including stem cells, polymer-based treatments, retraining and physical therapy".

Other researchers were intrigued but cautious. "It's work in progress," says Wagih El Masri, a spinal specialist at the Midlands Centre for Spinal Injuries in Oswestry, UK, who attended Curt's presentation. "We need larger numbers of patients treated to confirm whether this interesting finding has any future."

He says that about 3 per cent of patients show similar improvements spontaneously at about 6 months, but seldom beyond that. Testing the therapy on patients who were injured more than six months before would help to confirm that the stem cells are responsible for the results.

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