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Inflammation Sends SOS to Body Defenses

Researchers find the brain summons stem cells for help

FRIDAY, Dec. 10, 2004 (HealthDayNews) -- For anyone who's ever gotten a knock on the noggin, swelling hardly seems to be a good thing.

But inflammation is actually a vital part of the immune system, and a new study suggests it sends SOS signals to bring stem cells to the rescue, at least in the brain.

For now, the findings are preliminary. But the research could pave the way for better drugs to help the body heal itself.

According to study co-author Dr. Samia Khoury, an associate professor of neurology at Harvard Medical School, scientists didn't previously understand the "cross talk" within the immune system. "We have the first kind of road map to try to distinguish the steps from the initial injury towards repair," she said.

Inflammation occurs when the immune system rushes in to try to fix an injury. In some cases, as in rheumatoid arthritis, swelling can inadvertently cause even more problems by disrupting the way the body functions.

In the new study, Khoury and her colleagues induced mice to have a brain injury similar to a stroke. They then watched to see how the affected areas brought stem cells to the scene. "How do they get there? That's a question that hasn't been addressed," Khoury said. "How do they know where to go?"

The researchers report their findings in this week's issue of the Proceedings of the National Academy of Sciences.

The areas of inflammation sent out a chemical distress signal that called stem cells to the scene, Khoury said. Stem cells are essentially blank, designed to turn into something else. The topic of much controversy in medical research, they appear naturally in the brain. Once they get to the site of injury, "they start differentiating into different kinds of cells," Khoury explained.

In a way, it's as if a piece of metal appears at a construction site and turns into a wrench or a pair of pliers, depending on what workers need at the time.

The SOS might be set off by traumatic injury to the brain or the effects of disorders such as Alzheimer's disease, Khoury said.

The next step is to figure out how to control the cry for help. "Everyone is interested in how to get the stem cells into the right place," perhaps by using drugs, said Helen Blau, a professor of genetic pharmacology at Stanford University.

Meanwhile, the findings "may tell us that inflammation is beneficial in some cases, and in some cases it isn't," Blau said. "Even in the brain, it's not necessarily going to be beneficial."

More information

Learn more about inflammation from the Cleveland Clinic.

SOURCES: Samia Khoury, M.D., associate professor, neurology, Harvard Medical School, Boston; Helen Blau, Ph.D., professor, genetic pharmacology, Stanford University, Palo Alto, Calif.; Dec. 6-10, 2004, Proceedings of the National Academy of Sciences
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