A new stem cell treatment has shown promise in reducing the symptoms of Parkinson's disease.
Harvard Stem Cell Institute researchers at university-affiliated McLean Hospital implanted dopamine-producing neurons derived from the skin cells of primates, which survived for over two years after implantation into one of the animals and markedly reduced its Parkinson's symptoms.
Induced pluripotent stem cells were used in the experiment. This technique involves using a patient's own skin cells to create the stem cells and then the neurons, so they do not recognise the new dopamine-producing neurons as foreign and reject them.
"It's very difficult to get cell survival in primates," said Professor Ole Isacson, who has been refining his experiments for over 15 years. "This is a very high bar to clear."
He added that this experiment marked "the first time that an animal has recovered to the same activity level he had before".
Following treatment, speed of movement and levels of agility were the same as those of an animal without the condition, although individual motions were still slowed by the disease.
The latest experiment involved implanting neurons into only one side of the animals' brains, leading to improvements on the opposite side of the body, as expected.
Positive results were only witnessed in one animal because the experimental protocols evolved and were improved over time.
Originally, the neurons derived from embryonic stem cells were used in the experiments. This required using immunosuppressive drugs in the animals and did not produce results that were as positive as the latest study, which did not require immunosuppression.
Current treatments for Parkinson's include medications, electrical implants in the brain and, in a limited number of cases, fetal neuron transplants.
Symptoms of the condition include slowed movements, tremors, muscle rigidity, changes in speech and the loss of autonomic movement.
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