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.
The research was led by Jun Takahashi, a professor of neurosurgery at Kyoto University's Center for iPS Cell Research and Application (CiRA).
Takahashi's group is seeking to begin clinical trials on humans from next year in the hope that the treatment will become available five years after that.
Parkinson's disease is a long-term degenerative disorder of the central nervous system that causes limbs to shake as patients gradually lose control of their bodily functions.
The disease is caused by a reduction in nerve cells that produce dopamine, a neurotransmitter in the brain that helps control bodily movement.
About 150,000 Japanese suffer from Parkinson's disease.
Symptoms are relieved somewhat through drugs and by implanting electrodes into the brain, but as yet there is no treatment that stops the decrease of nerve cells.
The results of the research were posted Aug. 31 on the website of the British scientific journal Nature.
The research involved crab-eating macaques that were induced with Parkinson's disease. Nerve cells producing dopamine were created from human iPS cells and implanted into the brains of the monkeys.
Seven macaques were observed over a two-year period, during which their shaking and ability to move around showed a marked improvement.
Brain scans found an increase in the presence of dopamine.
The researchers were especially concerned about the safety of the treatment method. While the volume of transplanted nerve cells increased for about nine months after implantation, the amount remained unchanged thereafter.
Scientists confirmed that the implanted cells had not multiplied in an unusual manner or turned cancerous two years after the procedure.
However, the research team is still uncertain as to whether the effects of the transplanted cells continue after two years and if the cells remain safe.
"We were able to confirm the safety and effectiveness after a long period of observation of primates," Takahashi said. "We will now move to clinical trials in order to establish a treatment method."
Other groups have moved toward clinical tests on humans using iPS cells to treat other diseases.
Scientists at the Riken research institute are currently 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.
A team of researchers at Osaka University is planning to start clinical research from the first half of 2018 to treat heart failure using sheets of cardiac muscle cells created from iPS cells.
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