'Smart Cells' From Bone Marrow Help Rats Recover After Stroke

By Laurie Barclay, MD
WebMD Medical News

Reviewed by Dr. Jacqueline Brooks

April 5, 2001 -- Despite years of research, only one drug is available to reduce the amount of damage to the brain when someone has a stroke, and attempts to repair damaged brain cells have been largely unsuccessful. Now, for the first time, researchers have used cells from bone marrow to reverse disability following stroke in rats.

"This is a novel and important way to treat neurological injury and neurological disease, including stroke, spinal cord injury, and traumatic brain injury," author Michael Chopp, PhD, professor and vice chairman of neurology at Henry Ford Health Sciences Center in Detroit, tells WebMD. Chopp and fellow researchers published their results in the April issue of Stroke, Journal of the American Heart Association.

Researchers induced stroke in rats, then removed bone marrow cells and grew them in the laboratory. Like fetal cells, bone marrow cells can mature into a whole host of other cells when they're needed, making them potentially useful in treating different types of injury.

When the cells were injected back into the rats' veins, they zeroed in on the stroke-ravaged areas in the brain. Chopp calls them "smart cells." A few cells even began taking on some functions ordinarily carried out by nerve cells.

Compared with rats who did not get the bone marrow cells, rats injected with the experimental cells improved to near-normal levels within two weeks following stroke. They also had increased balance, coordination, and sensation.

"I would never have predicted that this would work, but something must have happened because the animals got better," Justin A. Zivin, MD, PhD, tells WebMD after reviewing the study.

"It's hard to understand how the cells get to the right place -- first they have to get into the brain, then they have to find the damaged areas and provide a beneficial effect once they get there," says Zivin, a professor of neuroscience at University of California, San Diego.

In other studies, cells from fetal tissue have been shown to improve function after brain injury, including stroke. However, using bone marrow cells has many potential advantages over fetal cells, including lack of rejection of the body's own tissue, and lack of ethical objections associated with using fetal tissue.

"It may not be necessary to limit our thinking ... to single sites of damage that can be specifically targeted in the central nervous system," Samuel Saporta, PhD, tells WebMD when asked for independent comment. "It may be sufficient to merely inject [cells] into the circulation and allow them to find all the sites in need of repair."

If so, injection of bone marrow cells might be helpful in multiple sclerosis and other neurological diseases where multiple sites are damaged, Saporta explains. He is a professor of anatomy and neurosurgery at the University of South Florida in Tampa.

Whether treated one day or one week after stroke, the rats had similar improvement, suggesting that therapy might be beneficial even if delayed. Such delayed treatment would be a major advantage, as many patients are not diagnosed promptly, and others are too ill in the first day or two after stroke to undergo removal of bone marrow cells. Still others recover spontaneously in the first day without any treatment.

While the researchers are applying to the National Institutes of Health to start early testing in humans, Zivin recommends that additional animal experiments be conducted by other laboratories to ensure the safety of this therapy.

"If you inject the cells [into the vein], who knows where they'll end up," Zivin tells WebMD. Bone marrow cells that go to normally functioning areas of brain might create problems.

"The FDA is wrestling with these types of problems right now in terms of stem cell therapy," Zivin says, adding that safety is more of a concern than whether or not the treatment will work. "But this is a promising beginning."