Nerve cells producing dopamine were created from human iPS cells and implanted into the brains of the monkeys.
Takahashi and his team researched a method whereby cells called “neural-precursor cells”, which have not yet developed into mature dopamine-producing neurons, are produced from human induced pluripotent stem (iPS) cells and then transplanted into the brain.
To assess the safety of the procedure, the researchers clinically followed the primates for 2 years.
Why are stem cells a promising treatment for Parkinson’s disease?
The main treatment of the disease is based on drugs mimicking the action of dopamine that is missing in the brain (levodopa or L-dopa), but that can, over time, cause significant side effects, such as abnormal involuntary movements, and also lose their effectiveness.
Parkinson’s disease degenerates a specific type of cells in the brain known as dopaminergic, or DA, neurons.
Any widespread use of the new therapy is still many years away, but the research has significantly reduced previous uncertainties about iPS-derived cell grafts.
What did the latest study find?
The varying outcomes suggested that the quality of the donor cells might play a role, so the researchers looked for genes that might explain the differences.
The research involved crab-eating macaques that were induced with Parkinson’s disease.
More important than the number of cells was the quality of the cells.
In addition, if the stem cells came from the patient’s own skin or blood, the problem would probably not arise in the first place, Takahashi said.
When will clinical trials begin and how will they work?
“This study is our answer to bring iPS cells to clinical settings”, said Takahashi. Such a trial would be the first iPS cell trial for Parkinson’s.
The results, reported in the journal Nature, were not the same for the dozen monkeys in the experiment, each of which received donor neurons from a different person. The use of fetal tissues is controversial, however.
But customized iPS cells are expensive to make and can take a couple months to derive and grow, Takahashi notes.
The treatment was performed by a team led by Jun Takahashi of the Center for iPS Cell Research and Application at Kyoto University, with results set to be released online in the British science journal “Nature” on August 31.
In monkey-to-monkey experiments, they found that the neuron transplants worked better across animals who shared similar gene groups responsible for shaping the immune system.
What other stem-cell approaches are being tested for Parkinson’s?
“We made DA neurons from different iPS cells lines”.
As those cells have not turned cancerous even after two years, the researchers said they had overcome a major hurdle toward confirming the safety of the treatment. But some researchers have expressed concerns that the immature transplanted cells could develop tumour-causing mutations. Eleven genes, especially one known as Dlk1, showed up in numerous most successful transplants, suggesting that screening potential donor cells may be critical. “We will now move to clinical trials in order to establish a treatment method”.
Scientists at the Riken research institute are now conducting clinical tests to verify the effectiveness and safety of a procedure involving the transplanting of retina tissue created from iPS cells into patients suffering from age-related macular degeneration, an intractable eye disease. “This shouldn’t be a race and we’re cheering for success by all”, she says.