Missing link stem cells may speed race for cures

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"Missing link" stem cells may speed race for cures

Wed Jun 27, 2007 1:31PM EDT

By Ben Hirschler

LONDON (Reuters) - Scientists have discovered a new type of embryonic stem cell in mice and rats that should speed up research into regenerative medicine and help in the hunt for cures to a range of diseases.

Two independent teams from Britain's Oxford and Cambridge universities said on Wednesday that so-called rodent epiblast stem cells were very similar to human embryonic stem cells, making them particularly good models for analyzing human health.

The new cells effectively constitute a "missing link" between mouse and human embryonic stem cells, according to Pedersen, leader of the Cambridge group.

Human embryonic stem cells are the source of every cell, tissue and organ in the body. Scientists want to use them to find cures for diseases like Parkinson's, cancer and diabetes, although critics say it is wrong to use any embryo in this way.

Laboratory mice have long been a favourite model for human disease but researchers have been frustrated by the fact that human and mouse stem cells behave very differently.

Now scientists think they may have cracked the problem.

INSIGHT

Two papers published in the journal Nature show that when mouse stem cells are derived from the innermost cell layer -- or epiblast -- of a week-old rodent embryo they are in many ways almost identical to human ones.

"Ultimately, we have to admit that mice aren't humans," Pedersen told reporters. "But we now have a much better model than we previously had."

Up until now, scientists have grown embryonic stem cells from the blastocyst, a very early-stage embryo not yet implanted into the womb. The new cells are taken after implantation.

Because they are further along the developmental timeline, they may offer a unique insight into how stem cells start producing mature cell types, like neurons, muscle and bone.

Pedersen -- who left the United States in 2001 to work in Britain because of curbs on federal funding of stem cell work -- said the hope was to work out how to control their growth and differentiation, in order to regenerate cells as a way to cure injuries and disease.

Gardner, who led the Oxford team, said the latest discovery should also help researchers derive stem cells in other species, including agricultural livestock.

That may provide different avenues for medical research, since some larger mammals are known to be better models of human disease than rodents. Sheep, for example, are a particularly good proxy for studying cystic fibrosis.

The use of epiblast stem cells will not lead to immediate breakthroughs in clinical treatments but the fact that two teams made the discovery almost simultaneously is a sign of momentum picking up in stem cell research.

"We are reaching a critical mass of understanding about these cells which should enable us to make the most of them in coming years," Gardner said.