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New Zealand scientists have discovered a cell pathway through which the adult brain may repair itself, opening a new line of research into future treatments for crippling diseases like Alzheimer's, Parkinson's and stroke.
This leap forward in understanding the human brain, by neuroscientists at Auckland University and at the Carlsson Institute for Neuroscience in Sweden, will be published as the cover story next week in one of the world's leading science journals, Science.
"It's pretty exciting," Auckland University's Professor Richard Faull, one of the leaders of the eight-year study, said yesterday.
Neurological diseases like Parkinson's, Alzheimer's Huntington's, stroke and epilepsy affect one in five New Zealanders.
Professor Faull's group showed in a study published in 2003 and based on its collection of donated brains that the human brain produced stem cells. These are cells which can divide and differentiate into other types, acting as a repair system by replenishing other cells that have been damaged or destroyed. That study showed that the brain tries to repair itself.
Professor Faull said the next question was whether, like rats, humans' brain contained a cellular pathway through which these new stem cells passed.
Other groups had looked, finding evidence suggestive of the beginnings of the pathway, but the Auckland-Sweden collaboration, by slicing brain tissue in a different way from others, was the first to trace the path of the human "neurogenesis motorway".
It extends from the so-called subventricular zone deep within the brain, where neural stem cells are created, to the olfactory bulb (which relates to the sense of smell). It was traced using techniques including magnetic resonance imaging (MRI) and the staining of cells.
Professor Faull said, "What's so important about this pathway is that in humans, of the cells that go down it, only a small proportion, 10 per cent, must go into the olfactory bulb.
"With the others, the question now is where they go. There are points they may leave the pathway early and go off to other parts of the brain. They could form new neurones in other parts of the brain.
"The challenge is to understand what makes these cells divide and migrate down the pathway. How can we increase that; how can we help stimulate the cells to travel to areas of brain damage. We know that in a rat, if it has the equivalent of Parkinson's disease or stroke, cells leave this pathway to go to areas of damage. The pathway in humans probably has the same facility.
"The excitement from this pathway is if we can try and develop an understanding of what makes these cells multiply and travel - if we could enhance this to help people who have brain cells die.
"This provides an opportunity to try and increase the pathways of brain repair in patients who suffer the loss of brain cells."
Professor Faull thanked the families who had allowed the brain of a loved-one to be donated to the Neurological Foundation Human Brain Bank.
"It has been a 20-year development of a research programme ... It shows Kiwi ingenuity and fresh ways of looking at the human brain pay off."
Max Ritchie, executive director of the foundation, which contributes financially to the support of the brain bank and to two of the researchers in the collaboration, said the study was an outstanding accomplishment for the New Zealand neuroscientists.
