2002-08-26 17:01:09 -0400
By Maggie Fox
Versatile human bone marrow cells injected into rats traveled to the animals' brains on their own and helped fix some of the damage caused by strokes, researchers said on Monday.
They said their experiment suggested that donated bone marrow cells might be used as a treatment not only for stroke but for Parkinson's disease and spinal cord injuries.
"We could have cells sitting on the shelf. When someone comes in, you give them a shot of cells," Michael Chopp of Henry Ford Hospital in Detroit, Michigan, who led the study, said in a telephone interview.
Bone marrow cells are used now to treat cancer, but donors and recipients must be carefully matched so the recipients' immune systems do not destroy the donated cells.
But Chopp and colleagues found that their bone marrow cells seemed to be able to slip by the rats' immune systems and take up residence where needed, pumping out chemicals that help brain and nerve tissue repair itself. Chopp said the cells used by his team lacked some of the surface proteins that usually activate the immune system to attack foreign cells.
"These are smart cells that selectively migrate to the site of injury and become little factories producing an array of helpful molecules to repair the tissue," said Chopp, whose team's findings are published in the journal Neurology.
"We believe this therapy shows promise in treating stroke, Parkinson's disease, spinal cord injury and traumatic brain injury."
There are drugs on the market to treat stroke, but to have any effect they must be given within hours of the stroke. Many patients do not get to the hospital in time, said Dr. Thomas Kent of the University of Texas Medical Branch in Galveston.
TIMING IS CRITICAL
"Many people still don't recognize the symptoms of stroke and get to an emergency room quickly enough for treatment. If this new treatment is effective, it could expand the treatment window by several hours or even longer," Kent, who wrote a commentary on the study, said.
Chopp stressed that the cells his team used are not the highly publicized stem cells--progenitor or master cells that can grow a variety of new tissues.
The cells his team used are called stromal cells, and rather than growing into replacement neurons, they seemed to secrete various chemical "factors" that stimulated repair of the cells damaged by stroke.
For their experiment, the team artificially caused a stroke in rats and then waited a week before infusing the human bone marrow cells intravenously.
A week after that, the rats were tested for various abilities that can be affected by a stroke, such as walking and balancing, and for reflexes.
The treated rats completed the tests 60% faster than the non-treated rats, and saw 30% improvement overall. Chopp thinks this means people could be treated effectively for days or weeks after suffering a stroke.
"In (the) rat we actually see better benefit when we infuse the cells a week after injury," Chopp said. "That is probably equivalent to a few months in a human.
Many more tests are needed before such an approach could be tried in human patients, however.
"It's not clear how long the window of opportunity might be," Kent cautioned. "We also don't know the long-term benefits and consequences."
Stroke is the third leading cause of death in the United States, killing nearly 160,000 Americans every year. Every year, an estimated 750,000 Americans have a stroke -- caused either by a clot in the brain or by a burst blood vessel.
Strokes kill brain tissue and can lead to partial paralysis, loss of
speech and other disabilities.
Copyright © 2002 Reuters Limited