Lab rats' severed spines repaired

THE SCIENTIST who grew a human ear on a mouse's back says he can repair severed spines - and has proved it by forcing formerly paraplegic rats to swim for their lives.

Although the procedure by Dr Charles Vacanti, of the University of Massachusetts Medical Center, has raised ethical questions, it could bring hope for people who have lost the use of their limbs through spinal injury or deterioration.

In his experiment he took nerve cells from dead rats, separated them out and grew them on a protein "scaffold", to form independent "neurospheres". He then took healthy rats, removed a one-inch section from their spines, and implanted the separately grown neurospheres into the gap.

The nerve cells then regrew to join the two sides of the severed spine. To prove that the transplant had succeeded, Dr Vacanti threw the rats into a bucket of water where they either had to use their previously paralysed hind limbs - or drown. "It's very motivating for them," Dr Vacanti told a conference in London yesterday.

Other scientists yesterdaywondered whether the work would be repeatable. "We all like to talk about our best, one-off results," said one who saw Dr Vacanti's presentation.

It is also hard to know how useful the approach might be for people with long-standing paraplegia. "We only know about the usefulness for acute injury," Dr Vacanti said. He suggested that all nerve tissue contains "immature" cells, which try to regrow after injury, but are prevented from doing so by scar tissue.

Dr Vacanti is no stranger to controversy. He first came topublic notice in 1995, when a picture of a mouse carrying the "scaffolding" for a human ear transplanted on to its back became an icon for ethically disputed science. He is also working with his brother Jay on an artificial womb that will be able to bring a baby to term outside its mother's body.