A new US study has shown that following neural stem cell injections, primates with severe Parkinson's disease show temporary recovery of their ability to stand, walk, feed and generally coordinate movement. Although the results are promising, it will be years before the therapeutic value for humans is known, according to lead author D. Eugene Redmond Jr., professor of psychiatry and neurology at Yale, whose team along with teams at Harvard, the University of Colorado and the Burnham Institute published the studies in Proceedings of the National Academy of Sciences.
Parkinson's disease results from the degeneration of neurons in the midbrain region which produce dopamine, a neurotransmitter essential for movement control and balance. On average an estimated 1 in 500 suffer from this currently incurable, debilitating disorder.
The new study is significant because it gained insight into how injected stem cells improve impaired cellular function. Rather than replace malfunctioning or missing cells with healthy ones, as previously suggested, it seems that only a minority will do this while others 'exert their behavioural effects through a series of mechanisms,' explained stem cell biologist Evan Snyder from the Burnham Institute in California, 'There's a whole network of activity and crosstalk'.
It appears the stem cells migrated to dopamine-producing regions and mainly served to boost the brain's internal repair system. Some became astrocytes, neural cells that produce chemicals that support neuron function. Other stem cells appear to have developed into cells that protect the brain from further deterioration, such as by producing anti-inflammatory and growth factors to enhance dopamine function, or via blood-vessel development.
The improvements subsided after approximately four months, probably due to the monkeys' immune systems attacking the stem cells. New studies using immunosuppressive drugs and continued treatment will be done to see if the benefits can be prolonged.
Eight African green monkeys were injected with a chemical that damages neurons responsible for dopamine production. Their chemically-induced Parkinson's symptoms were studied for four months. Then five primates were injected with human neural stem cells, which were not embryonic, but technically 'adult' stem cells from thirteen-week-old aborted fetuses. The monkeys were observed for four months and those which received stem cell treatments had a dramatic improvement of symptoms. Their prognosis remained better than the other monkeys throughout the four months even after the improvements began to regress. Twenty-one other monkeys were studied for up to eight months to further understand how the stem cells function. No tumours or toxic effects were found and no atypical primate behaviours resulted from the human neural stem cell treatment.
Sources and References
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Neural Stem Cells Reduce Parkinson's Symptoms In Monkeys
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Human stem cells treat Parkinson's in monkeys
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Stem cells help primates with Parkinson's
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