Umbilical cord blood, often discarded after birth, may offer a vast new source of repair material for fixing brains damaged by strokes and other ills, free of the ethical concerns surrounding the use of fetal tissue, researchers said.

In animal experiments, at least, cells from umbilical cords appear to greatly speed recovery after strokes. They work with a simple infusion into the blood stream without the need for direct implantation into the brain.

Although many details need to be worked out, Dr. Paul R. Sanberg of the University of South Florida said he hopes to try the approach on stroke victims within the next year or two.

Sanberg described the research at a meeting in San Francisco of the American Association for the Advancement of Science. It was financed by the state of Florida and Cryo-Cell International Inc. of Clearwater, Fla.

Many experts believe that primitive tissue called stem cells will someday be routinely used to make human spare parts. They might replace tissue damaged by many different diseases, especially such brain ailments as strokes and Alzheimer's disease. These generic cells can be nudged to develop into all sorts of specialized tissue to repopulate every part of the body from head to toe.

One source of stem cells is aborted fetuses or fertility clinics' discarded embryos. However, this is especially contentious since anti-abortion groups oppose fetal and embryonic stem cell research, and federally funded scientists cannot use stem cells from these sources.

Sanberg said his research suggests that umbilical cords could be an excellent source of stem cells without the ethical headaches of fetal tissue. He noted that 4 million babies are born in the United States each year, and 99 percent of their cord blood is tossed away.

He said one or two cords could probably provide enough stem cells to treat one human stroke victim, if the current approach proves useful. The cells could be frozen for use when needed.

In experiments so far, his team removed stem cells from cords and then used retinoic acid and growth hormones to transform them into immature nerve cells. They then injected 3 million of these cells into the bloodstreams of rats that had suffered strokes.

In experiments on about 60 rats, the team found that after one month, those given the cells had recovered about 80 percent from their strokes, compared with about 20 percent in untreated rats.

Sanberg said the treatment works best when given within 24 hours of a stroke but still helps up to a week later. Just how the new cells rewire the damaged parts of the brain is unclear, although the cells can take on the form of distinctly different types of brain tissue, and they also appear to prompt damaged cells to repair themselves.

"They are attracted to the stroke part of the brain more than the normal brain," he said. "Some signal is being sent that attracts them."

Sanberg cautioned that many questions remain, such as whether the cells should be given in several doses, how many should be infused, and whether the treatment will require suppression of the immune system, since the body might otherwise reject the foreign tissue.

"This is very exciting," said Dr. Sandra Chapman of the University of Texas at Dallas.

"The potential of this will be an exponential improvement in our chance of treating all sorts of brain disorders."

Associated Press February 19, 2001