New blood in old veins

As if by magic, scientists turn brain cells into blood: an achievement that could let cells develop their own tissues

Published: Monday 15 March 1999

 Cells: from brain to blood<sc (Credit: science photo library)going by how easy it has been for scientists to turn adult brain cells to blood, it will not be difficult to use a patient's own tissue and grow replacement organs. Earlier, scientists thought such radical identity swaps involved nuclear transfer, a technique that 'made' Dolly, the world's first cloned sheep. Such techniques usually involve replacing an egg cell's own genetic matter with the transplanted nucleus of an adult cell.

But now, says an international team, such dramatic metamorphoses need not involve equally dramatic and complicated methods. Simply injecting the neural stem cells (nscs) from the brain into mice bone marrow is enough. If the same works in humans, the new method could lead to perfectly matched transplanted tissues, sans the use of embryonic stem cells taken from aborted foetuses.

Until a couple years ago specialisation, the process in which embryonic stem cells change to form tissues, was thought to an irreversible process. Then came Dolly the cloned sheep, whose creators demonstrated that an adult cell's potential for development could be harnessed. Dolly's creators, from Edinburgh's Roslin Institute, think that factors in the egg 'reprogram' the cell's genes to an embryonic state so that it can form any kind of tissue. Dolly was born from one such 'reprogrammed' udder cell.

Angelo Vescovi from the National Neurological Institute in Milan, Italy and his team wanted to see if this reprogramming could be done without going in for cellular surgery. They thought that the nscs, brain's least specialised cells and the basis for all other brain cell types, could hold some promise. His team injected nsc s from adult mice into mice bone marrow that had been exposed to enough radiation to cripple the blood-producing cells. Vescovi thought that this new environment might trigger the reprogramming. He could not have been more right. After five months, the recipients developed new blood cells. Genetic analysis confirmed that many of these new blood-producing cells were direct descendants of the nscs, Vescovi and his team reported in a recent issue of Science.

According to Vescovi, this time lag fits in perfectly with the idea of the cells being reprogrammed. It suggests that the cells must first reverse their development to a near embryonic state before they begin to develop into the new tissue. His latest results show that the blood cells are functional: mice exposed to radiation and then implanted with nscs lived longer than those that were irradiated but did not receive the nscs.

Talking to the British science journal New Scientist (Vol 161, No 2171), John Gearhart of John Hopkins University in Maryland, usa, said, "It's a totally new observation, it's very striking." Gearhart's team recently had the distinction of isolating human embryonic stem cells.

Vescovi believes it may be possible to use stem cells from other tissue such as skin as the source of new tissue. These would be far easier to obtain than the brain stem cells he has used so far.

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