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Amniotic fluid supplies 'repair kit' for later life
13 January 2007
From New Scientist Print Edition.

MOTHERS could bank a reserve of spare tissue for their child at birth now that stem cells have been discovered in the amniotic fluid surrounding infants in the womb.

Alternatively, cells from many babies could be stored in a public tissue bank. The huge number of samples on tap would mean that almost every patient would be able to find a match if they needed "off-the-peg" tissue.

The cells, termed amniotic fluid-derived stem (AFS) cells, appear to be "halfway houses" between embryonic stem cells (ESCs), primitive cells in embryos capable of turning into every cell in the body, and adult stem cells, partially differentiated cells dispersed around the body which replenish and repair specific tissues during life.

"They have the properties of both," says Anthony Atala, head of the team that isolated and tested the AFS cells at Wake Forest University School of Medicine in Winston-Salem, North Carolina. "So far, we've shown they can grow into nerve, blood vessels, liver cells, cartilage, bone and cardiac muscle," he says.

AFS cells could supply a ready source of stem cells for therapeutic treatments. Doctors could either extract the cells from amniotic fluid sampled for prenatal testing, or from the placenta once the mother had given birth. The cells could then be preserved in liquid nitrogen - theoretically, for years. If the individual later needed a tissue or organ transplant, the cells could be grown into a perfect graft which the body wouldn't reject.

At least that's the theory. So far Atala has shown that AFS cells grow into almost as many types of tissue as ESCs, and just as quickly - doubling in number within 36 hours. Equally encouraging, nerve cells created from human AFC cells successfully integrated with brain cells in mice, suggesting the technique could potentially repair tissue in humans.

Other researchers welcomed the findings, published online in Nature Biotechnology (DOI: 10.1038/nbt1274). "If the cells can be extracted from the placenta, it's a very convenient way of getting large numbers of cell lines that repair all types of cells," says Ian Wilmut of the University of Edinburgh, UK, who was part of the team that created Dolly, the first cloned sheep.

"It's likely that therapies will arise from cells like these way before they're available from embryonic stem cells," adds Lyle Armstrong of the University of Newcastle upon Tyne, UK. A separate team at Newcastle has been working with similar cells found in umbilical cord blood, which have the potential to mature into a smaller range of tissues.v The discovery of AFS cells doesn't make ESCs redundant, however. ESCs are controversial because so far the only way to collect them is by destroying early embryos. But all the teams insist that ESCs will be invaluable, especially for understanding diseases and testing new drugs. Wilmut, Armstrong and a third team led by Stephen Minger of King's College London were expected to hear this week whether their application to generate ESCs from "cow-human" or "rabbit-human" embryos in the UK has been successful.

From issue 2586 of New Scientist magazine, 13 January 2007, page 9

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