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A new study published online in the March 15-19 early edition of the Proceedings of the National Academy of Sciences borrowed its idea from the field of organ transplantation, where multipotent stem cells in the form of bone marrow transplants are already used to reduce the risk of rejection in patients who have received donated organs.
Senior study author Dr. Eva Mezey, head of the adult stem cell unit at the National Institute of Dental and Craniofacial Research (NIDCR), cautioned that this was an early-stage experiment conducted only in mice, and humans shouldn't get too excited just yet.
"On the one hand, people should be cautious that it might not be just as good in people. However, there are many human studies that have proven that these cells are able to modulate the immune system and tip the balance back to normal when the balance is gone," she said. "It's very likely that the intervention would work in humans."
But clinical trials will depend on working out numerous details, including how the therapy would be delivered. In the mice, the stem cells were injected but aerosol administration might work better in humans, producing a more local result instead of systemic effects and, probably, fewer side effects, she noted.
And this stem cell therapy, if it ever reaches patients, is likely to be reserved for those who haven't responded to other therapies. "Basically, you would think of this therapy in cases where patients are resistant to existing treatment," Mezey explained.
Some 16 million people in the United States have asthma, and the incidence seems to be on the rise.
Because bone marrow transplants quell immune responses in transplant patients, the idea was that it might be beneficial in individuals with other immune-based diseases such as asthma.
Here, the investigators used mice that had been engineered to be allergic to ragweed and injected them with multipotent stem cells known as bone marrow stromal cells. Multipotent stem cells are cells that can develop into many different cell types.
"We gave the mice intravenous injections of stem cells and, after four days, we assessed different mediators of the inflammatory response and that's how we could pick up the beneficial effects of the stem cells," said study first author Dr. Krisztian Nemeth, a research fellow with the adult stem cell unit of NIDCR.
After that, he added, "we went into more accurate details and tried to explore what anti-inflammatory molecules were synthesized by our cells and how they mediated the anti-inflammatory response."
It turned out that the stem cells righted the balance of certain white blood cells that are out of sync in those with asthma.
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