ONE OF the most exciting developments in modern medicine - the use of stem cells derived from human embryos to treat a range of debilitating and incurable disorders - has been dogged by ethical controversy. But now scientists have made a breakthrough that could undermine the case for using embryonic stem cells at all. New evidence suggests that cells derived from a patient's own bone marrow may regenerate damaged nerves in the brain, a task once considered impossible.
The work has potential to challenge embryonic stem cell research because these stem cells have come not from embryos but from the bone marrow of a mature adult. It also represents an important breakthrough in the treatment of illnesses such as Parkinson's, multiple sclerosis and Alzheimer's disease.
It is the latest evidence to emerge from several lines of research that have pointed to the power of adult stem cells to "re- invent" themselves rather than to be narrowly predestined to develop into just 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 given that adult stem cells appear to possess the same all-round ability to develop into specialised tissues. 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 of their ability to be cultured in the laboratory and stimulated with chemicals to become any one of the scores of specialised tissues of the body.
Scientists envisage a day when stem cells can be used to repair damaged organs, such as heart, brain or kidney, rather than having to opt for potentially toxic drugs, a transplant operation or palliative care for the terminally ill.
Several sources of stem cells have been identified, such as "spare" IVF embryos less than 14 days old or adult bone marrow which is constantly regenerating to produce fresh blood cells. The question has been whether adult stem cells are just as good as embryonic stem cells in terms of "pluripotency" - the ability of a cell to become any specialised cell of the body.
Work on animals demonstrates the power of cultured embryonic stem cells to develop into any tissue, but adult stem cells were traditionally thought to be more fixed in terms of what they could become - bone marrow should only develop into blood cells for instance. However, the latest research, led by Walter Low, professor of neurosurgery at the University of Minnesota Medical School, demonstrates that bone marrow extracted from adult mice can actually develop into fully functioning, 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 normally 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's, said the bone marrow stem cells developed into all the cells known to be implicated in Parkinson's disease, Huntington's disease, ataxia and Alzheimer's disease. "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 indicated that adult bone marrow cells may have the ability to develop into non-blood tissue. …