Two new studies show that bone marrow could be used as a source of brain stem cells - 'master' cells that can replicate and grow into a variety of brain cell types. The findings mean that bone marrow transplants could eventually be used to treat brain injuries and illnesses such as Alzheimer's disease, say the researchers.

The teams of scientists, based at the US National Institute of Neurological Disorders and Stroke (NINDS) and Stanford University, California, showed that bone marrow cells transplanted into mice give rise to new brain cells, as well as new blood cells. The new brain cells included neurons - cells that transmit nerve impulses - in addition to glial (support) cells. Both studies were published in last week's issue of Science. An accompanying article in Science stresses the need for further research on both adult and embryo stem cells to realise their full therapeutic potential.

Professor Richard Gardner, chairman of the UK's Royal Society working group on 'therapeutic cloning' - the use of cloned early embryo stem cells to treat disease - said the latest results were 'interesting and exciting'. But he pointed out they did not prove that adult human stem cells could ever provide the full range of cell types required for treatments. 'Research on human embryonic stem cells is still essential' he said.