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Thursday, 24 February, 2000, 13:00 GMT
Bird brains offer stem cells hope

Human stem cells: Potential to revolutionise medicine
Human stem cells: Potential to revolutionise medicine


By BBC News Online science editor Dr David Whitehouse

Scientists have coaxed new brain cells to grow from adult stem cells. The work was done using bird brains and exploits the power of these special cells to become any type of tissue in the body.

Researchers have high hopes that stem cell technology will prove useful in the treatment of human brain diseases such as Parkinson's and Alzheimer's.

Human stem cells Scientists want to be able to direct the specialisation of stem cells
By destroying certain brain cells in zebra finches, the scientists say they have prompted the growth of new brain cells. Describing their research in the journal Neuron, they say they believe that neural stem cells must be the source of the new neurons.

"This is, we believe, the first example where it has been demonstrated that one can induce the birth of new brain cells and that they actually contribute to a complex behaviour," said Jeffrey Macklis, a neuroscientist at Harvard University.

"It is a step toward attempting the same in mammals," he added.

Bird brain

The researchers chose zebra finches because of an interesting variation in bird biology.

Canaries stop singing every autumn when a population of brain cells responsible for song-generation die. Over the winter, a whole new population of neurons grows back and in the spring the canaries learn their songs all over again.

But zebra finches lack this seasonal cycle. Instead, their brains generate a continuous trickle of new neurons.

Until recently, scientists believed that brain cells did not regenerate, but they now know that new cells do grow to a limited degree, especially in brain regions called the olfactory bulb and the hippocampus. One theory receiving serious attention holds that when certain neurons die, they signal stem cells to produce replacements.

Macklis's team selectively killed one kind of song-related neuron in their zebra finches. The birds, as predicted, partly lost their ability to sing. But three months later, they were singing as normal.

When the researchers looked at their brains, they saw that the neurons had grown back, in much the same way that canary neurons come back. They say they are now performing more experiments to see just where the new cells came from, but they suspect they coaxed stem cells into action.

Controversy

Stem cells are cells that can develop into other types of cells and as such they have the potential to be used to replace cells that have been lost of damaged.

The new-found ability to grow stem cells from human embryos in the laboratory was hailed by Science magazine as one of the major breakthroughs of recent years.

Scientists are trying to find ways to use either adult or embryonic stem cells, or both, to regenerate various forms of tissue, including brain cells of patients with diseases such as Alzheimer's or Parkinson's.

They are, however, difficult to isolate and grow. Controversially, they can be taken from aborted foetuses or from embryos left over from IVF (test-tube) fertilisation programmes. In many countries, this is illegal.

Some researchers say that there may be a solution to the ethical problems of obtaining stem cells from embryos. Many tissues in the human body contain stem cells. Usually they develop into more cells of the tissues they are in, but there is hope that they can be re-programmed.

There is some recent evidence that these stem cells can be enticed to go back to an unspecialised 'blank' state. This line of research has the promise to obtain stem cells without using human embryos at all.

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See also:
05 Jan 00 |  Sci/Tech
Lab grows frog eyes
17 Dec 99 |  Sci/Tech
Stem cells top class of 1999

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