Adult way out of Stem cell dilemma

By STEVE CONNOR

The use of stem cells from human embryos to treat debilitating and previously incurable disorders is one of modern medicine's most exciting developments - and one which has been dogged by ethical controversy.

But scientists have made a breakthrough that could remove the need to use embryonic stem cells.

They have found that cells from a patient's own bone marrow may regenerate damaged nerves in the brain, something once considered impossible.

The discovery could challenge embryonic stem cell research because these stem cells come not from embryos but from the bone marrow of a mature adult.

It is also an important breakthrough in the treatment of illnesses such as Parkinson's disease, multiple sclerosis and Alzheimer's disease.

It is the latest evidence to emerge from several lines of research that have indicated the power of adult stem cells to "reinvent" themselves rather than be predestined to develop into one type of body tissue.

The findings, published in the journal Cell Transplantation, will reopen the debate over the ethics of experimenting on stem cells taken from human embryos.

Anti-abortion groups and the Vatican have fiercely opposed the use of human embryos in stem cell research.

Stem cells have become one of the most exciting areas of medical research because they can be cultured in the laboratory and stimulated with chemicals to become any one of the body's scores of specialised tissues.

Scientists envisage a day when stem cells can be used to repair damaged organs, such as heart, brain or kidney.

Stem sources include "spare" in vitro fertilisation embryos less than 14 days old and adult bone marrow which is constantly regenerating to produce fresh blood cells.

The question has been whether the "pluripotency" - the ability of a cell to become any specialised cell of the body - of adult stem cells is as good as embryonic stem cells.

Work on animals showed the power of cultured embryonic stem cells to develop into any tissue.

But adult stem cells were thought to be more fixed in terms of what they could become - bone marrow should only develop into blood cells, for instance.

But the new research, led by Walter Low, professor of neurosurgery at the University of Minnesota Medical School, shows that bone marrow extracted from adult mice can develop into specialised brain cells.

Professor Low injected bone marrow cells from a mouse into early embryos, which were implanted into other mice who gave birth to live young.

The offspring were found to have taken up the "foreign" bone marrow stem cells and used them to make cells in all regions of the brain.

The transplanted stem cells developed into nerve cells, which conduct electrical impulses, glial cells which provide support to the nerve cells, and cells that produce the fatty myelin sheath around the nerve cells, which is damaged in patients with multiple sclerosis.

Catherine Verfaillie, a colleague of Professor Low, said the bone marrow stem cells developed into all the cells implicated in Parkinson's, Huntington's and Alzheimer's diseases and ataxia.

"This tells us that these adult stem cells are capable of becoming nerve cells that communicate with other nerve cells within the brain and form proper neural circuits that permit the mice to function normally," Dr Verfaillie said.

A number of studies have already found that adult bone marrow cells may be able to develop into non-blood tissue.

Scientists from the US National Institute of Neurological Diseases and Stroke in Bethesda, Maryland, found for instance that women who had received bone marrow transplants from men had brain cells containing the male Y chromosome.

The implication was that male bone marrow stem cells had migrated to the women's brains to become nerve cells, said Eva Mezey, who led the study.

"We have had trouble convincing some members of the scientific community that this could happen," Dr Mezey said.

Opponents of the use of human embryos in stem cell research are likely to use the findings to support their belief that there is no real need to experiment with human embryos.

Josephine Quintavalle, a British lawyer and campaigner, said she would use the work on adult cells to challenge whether scientists need to use human embryos at all. "Adult stem cells are infinitely better than embryonic stem cells," she said.

"The bias in the UK has been to use embryonic stem cells simply because we have the most permissive environment in the world for this sort of research."

But many British scientists and scientific organisations - such as the Royal Society - believe research on adult and embryonic stem cells needs to be done in parallel before any decisions are made to ban use of embryos.

A House of Lords committee's report on stem cells concluded: "It is unlikely that either adult stem cells or embryonic stem cells alone will provide the basis for all stem cell-based therapies.

"It is therefore necessary to keep both routes to therapy open to ensure maximum medical benefit."

Professor Low said further work was needed to ensure that the adult stem cells in his study were developing into specialised brain cells rather than merely fusing with them.

Professor Austin Smith, of Edinburgh University, found evidence to suggest that adult stem cells tend to fuse with other cells, which could make them potentially cancerous.

"If they only make other tissues by fusing with existing cells rather than producing new cells, their utility for tissue repair and regenerative medicine will be greatly reduced," Professor Smith said.

Professor Low said it was unlikely that his findings were the result of adult stem cells fusing with existing cells.

But he could not yet rule it out.

Further research this year should establish beyond doubt whether adult stem cells were truly capable of regenerating damaged brains.

Until then, he said, further work on embryonic stem cells and adult bone marrow cells was necessary to compare the remarkable attributes of both types of cell.

Stem cell debate

* Until now, most scientists believed that only undeveloped stem cells could "reinvent" themselves to cure diseases.

* The research is controversial because it involves the use of human embryos.

* A new study shows adult mouse cells from bone marrow can be converted into brain cells.

* Opponents say stem cell research should therefore be stopped immediately.

* Other scientists believe work should continue in both areas until the facts become clearer.

- INDEPENDENT