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Injecting Stem Cells Into the Brain Reverses Parkinson's Symptoms in Monkeys

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Stem cells injected into the brain could reverse some symptoms of Parkinson's. Here, human embryonic stem cells grow in culture. (Annie Cavanagh, Wellcome Images)

Injecting neurons created from stem cells into the brain may relieve Parkinson’s symptoms, according to a new study in monkeys.

Why it matters:
Parkinson’s disease can happen when some of a person’s dopamine-producing brain cells die, so replacing those neurons could be an effective treatment. Administering dopamine is part of currently accepted treatment, but over time the treatment has less effect as neurons die off and the side effects become difficult to manage. So scientists have begun studying approaches using stem cells, primarily in rodents. A clinical trial is also underway at the Royal Melbourne Hospital to inject neural stem cells into the brains of people with Parkinson’s as part of a Phase I clinical trial. Results are expected in 2019, and preliminary results were presented at the American Academy of Neurology meeting this year.

The nitty-gritty:

Researchers collected skin or blood cells from seven humans, some who had Parkinson’s disease and some who did not. (The people with Parkinson’s did not have any of the genes thought to be associated with the disease.) Next, using sets of proteins, they “reprogrammed” some of those cells and encouraged them to grow up as neurons — specifically, neurons that could produce dopamine. Finally, they injected the stem cells into the brains of monkeys that were treated with a neurotoxin, which made them act like they had the condition.

Researchers found that the symptoms of the monkeys treated with stem cells from either group improved more over the course of a year than monkeys treated with a placebo injection. To determine if the monkey’s symptoms had improved, the team evaluated their tremors, movements, and posture, among other things. The team published its results in Nature on Wednesday.


“I think that a stem cell-based therapy will bring more benefits than conventional treatments can do now,” said Dr. Jun Takahashi, a professor at Kyoto University and one of the authors of the paper.

You should know:
Among conventional treatments for Parkinson’s is a medication called L-DOPA, which ultimately helps patients replace some of the dopamine they can no longer produce. Another accepted procedure is deep brain stimulation, which sparked Takahashi’s interest in this project, he said.

Takahashi and his team did not run tests comparing their results to those seen after deep-brain stimulation and L-DOPA treatment, but they did compare their findings to published statistics. They concluded that the transplants “should exert [similar] effects.”

What they’re saying:
Dr. Lorenz Studer, director of the center for stem cell biology at Memorial Sloan Kettering Cancer Center, said Takahashi’s work was “a very impressive study,” especially given the number of animals, the length of time they were followed, and the similarity of the protocols used to those that might be used in human trials. “In this regard, it was a really interesting test run,” he said.

“It is probably the best study to date using the induced pluripotent stem cells,” said Studer, who was not involved in the research.

But keep in mind:
The study isn’t without limitations. Studer noted that the volume of neurons that survived varied widely between monkeys, with no clear behavioral impact. Additional, he said that this paper didn’t particularly characterize cells that were not dopamine-producing. “Whatever they are, they didn’t really cause any problems,” he said. “In the clinic, that’s kind of important to know.”

And more research should also be done to figure out how to identify cell lines that would work best in this kind of treatment, the paper noted.

Takahashi said he plans to start clinical trials in 2018.

The bottom line:
This study adds more convincing animal evidence of the promise of stem cells in treating Parkinson’s disease, and human trials may soon give an even clearer picture.

This story was originally published by STAT, an online publication of Boston Globe Media that covers health, medicine, and scientific discovery.

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