Brain cells taken from fetuses may be able to replace some of those killed in a stroke, U.S. researchers reported on Monday.

Implanting the brain cells in rats showed that the immature brain cells found their way to the area of stroke damage and stayed alive - an important feat, because the damage caused by stroke often kills off neighboring cells, too.

The cells may also offer a way to treat devastating brain diseases and spinal cord injuries, the team at Stanford University in California said.

“It’s the first time it’s been shown that such a human cell can survive, migrate and differentiate in a stroke environment, which is not the most favorable environment,” said neurosurgeon Gary Steinberg, who led the study.

Steinberg’s team used cells that were originally taken for aborted fetuses years ago and that have been growing in laboratories run by Palo Alto-based StemCells, Inc.

The brain cells “are not embryonic stem cells,” Steinberg said, referring to controversial cells taken from days-old human embryos. “They are from a line established many years ago and should not be as controversial.”

Stem cells are immature cells that have the potential to give rise to any number of different kinds of cells and tissues. There are various sources, from the bone marrow to fetal tissue to embryos. Use of embryonic cells is controversial, because of philosophical differences over the nature and beginning of life.

Steinberg’s team tested the fetal brain cells in rats given an artificial stroke.

Writing in the Proceedings of the National Academies of Science, they said the cells lived for as long as a month in the rats and also found their way to the site of the stroke.

“These are smart cells,” Steinberg said in a telephone interview.

“Why do these cells migrate toward the stroke? We think and have some preliminary evidence that it is due to chemicals or chemokines being released in the stroke area.”

Chemokines are chemical signals released by cells - a kind of molecular call for help in this case.

Now his team is evaluating the rats to see if the cells did them any good. Stroke can cause paralysis, loss of language and other problems in people.

Steinberg said it is not yet clear whether immune-suppressing drugs such as cyclosporin would have to be used to prevent the body from rejecting the cells. The rats were given the drug.

Next Steinberg says his team plans to use the cells in human experimental trials for a “devastating brain disease” but said he could give no details.

Stroke is the third leading cause of death in the United States, killing 167,000 people this year.