Stem cell transplant boosts function slightly in Parkinson’s monkeys

Researchers believe that someday treatments for Parkinson's disease will include transplants of dopamine-producing neurons, like these derived from human induced pluripotent stem cells.

In a small but hopeful step for researchers working on therapies to treat Parkinson’s disease, a team in Japan has used stem cells harvested from bone marrow to restore function in monkeys with the debilitating condition.

The cell transplants didn’t cure the macaques, but did improve motor skills in the animals and appeared to do so safely, the scientists wrote Monday in the Journal of Clinical Investigation — suggesting that stem cells from bone marrow might someday be a useful source for treatments of Parkinson’s in humans.


“To the best of our knowledge, this study is the first to show restoration of dopaminergic function and motor behaviors in parkinsonian primate animals” after treatment with stem cell-derived neurons, they wrote.

Stem cells are early-stage precursor cells that develop into the mature cells in the body. Scientists have long hoped to learn how to use them to replace cells and tissues damaged by accident or disease.

Parkinson’s has seemed like a good candidate for stem cell-derived therapies because people with the disorder have lost cells in the brain, or neurons, that produce the neurotransmitter dopamine. (For more about Parkinson’s read this page from the NIH’s National Institute of Neurological Disorders and Stroke.) If stem cells could be coaxed to develop into healthy, functioning dopaminergic neurons and then introduced into the brain, the thinking goes, perhaps patients could get relief from tremors, loss of balance and other debilitating Parkinson’s symptoms.

The Japanese team, led by Takuya Hayashi of the RIKEN Center for Molecular Imaging Science in Kobe, Japan, conducted its research on a group of 10 adult macaque monkeys. They induced Parkinson’s disease on the left side of the animals’ bodies.


They removed bone marrow from the hip bonesof the macaques, isolating so-called mesenchymal stem cells — the same type of cells that are sometimes harvested to treat patients with leukemia. (While mesenchymal stem cells can differentiate to become a variety of different types of cells including bone, cartilage and fat, they are not the same as embryonic stem cells or induced pluripotent stem cells, which can develop into any type of cell in the body.) The team used a previously reported method to turn the mesenchymal stem cells into dopamine-producing neurons.

Hayashi and his colleagues studied the neurons they created in the lab to assure that they were indeed dopamine-producing, and then administered treated cells to five of the monkeys. Each of the five monkeys received cells derived from his own bone marrow. The remaining monkeys received sham treatments.


Animals who received the cell treatments had improved motor function, the team reported. What’s more, through the use of PET scans and postmortem tissue analysis, the researchers determined that the implanted neurons continued producing small amounts of dopamine for at least nine months. The monkeys did not develop tumors, always a concern with stem-cell based therapies. Because the cells came from the monkeys’ own bone marrow, tissue rejection wasn’t an issue either. And the stem cells’ origin in mature animals — not fetuses — sidestepped availability issues and ethical considerations involved in using fetal tissue, the scientists wrote.

Before the treatment might be considered appropriate for humans, they said, further studies will be needed to improve the viability of the cells once implanted, and to boost their therapeutic effect. But, they added, the approach “may expand the availability of cell sources for cell-based therapies for patients with Parkinson’s disease.”