The end of stem-cell controversy?

7 June 2007

Ordinary skin cells can now be reprogrammed to make stem cells identical to those found in embryos. The breakthrough means scientists could make an endless supply of powerful stem cells - without harming any embryos. Antenna investigates...

This research was published on the journal Nature's website on 6 June 2007.

The new stem cells, above, look and grow just like embryonic stem cells.

Image: Marius Wernig/Nature

Ordinary cells are highly specialised to do a particular job. But stem cells are much more flexible. In embryos, they turn into all the different types of cell in the body. In adults, they act as the body's natural repair kit.
Scientists have been harnessing the power of human stem cells in the lab. Stem cells from embryos are more adaptable than those from adults, but using them is controversial because the embryos are usually destroyed when scientists harvest the cells.

Scientists are investigating if embryonic stem cells, above, can be used to grow replacement tissue and organs.

Image: iStockphoto.com/Andrei Tchernov

Could new research end the controversy?
Now, in a world first, three teams of experts from Japan and the US have created stem cells in mice that are identical to those found in mouse embryos, but which are made from ordinary cells. It's never been done without using mammalian eggs or destroying an embryo before.

These stem cells, made from skin cells, contain a protein that makes them glow green. This helps scientists pick them out from other cells.

Image: Shinya Yamanaka/Nature

Fibroblasts are found in connective tissue, which provides support and structure to the rest of the body.

Image: iStockphoto.com/Andrei Tchernov

The scientists took cells called fibroblasts from the skin of mice and used a harmless virus to 'infect' the cells with four genes. 'It's very easy to obtain these cells from the skin of mice, and humans,' explains stem-cell expert Shinya Yamanaka from Kyoto University in Japan.
After letting the cells divide and grow for several days, the scientists selected those that contained proteins found in embryonic stem cells.
'The cells are indistinguishable from embryonic stem cells in every way we know how to test,' explains stem-cell expert Marius Wernig, from the Massachusetts Institute of Technology in the US. 'This means all the research carried out so far using embryonic stem cells should apply to these new stem cells.'

Marius Wernig, Massachusetts Institute of Technology.

Image: Flora Lichtman/Science Friday

The stripes in this mouse's fur show it's a 'chimera' - some of its cells came from an original embryo, and some came from stem cells injected into the embryo.

Image: Marius Wernig/Nature

The stem cells are so similar to those found in embryos that the scientists could inject them into early mouse embryos, and the embryos would still develop into adults. But the technique isn't perfect yet - some of the adult mice developed cancer.
The tumours were caused by one of the four genes used to create the stem cells. 'One way to avoid this is to find a small molecule that mimics the function of the gene,' explains Shinya.
'This is a crucial area of research if we are to use these cells in regenerative medicine. If we can overcome the problems, we should be able to use these stem cells for transplants that won't be rejected by a patient's immune system.'

In 2006, Shinya (above) and his team showed it should be possible to turn skin cells into 'embryonic' stem cells - now it's been done for real.

Image: Shinya Yamanaka

Reprogramming ordinary cells this way is probably the future of stem-cell science, according to stem-cell expert Julia Polak from Imperial College London. 'It's a major step forward, and it doesn't use embryos,' she says.
'But the research was carried out in mice - the big question is will it work in humans? If it does, it opens up potential therapies in an amazing way.'

Julia Polak, Imperial College London

Image: Julia Polak

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