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Gene Insights Could Boost Blood Supply

Extending the life span of platelets may stretch product storage time, experts say

THURSDAY, March 22, 2007 (HealthDay News) -- A new discovery by Australian scientists could greatly extend the shelf life of donated blood.

The team says they've gained a greater understanding of the internal clock in blood components called platelets, potentially paving the way toward ways to keep them alive longer.

Now, platelets only survive for about a week, making it a challenge for hospitals and blood banks to guarantee they're available when needed for certain kinds of transfusions.

In addition to helping preserve platelets, the research could lead to new medications, said Dr. Thomas P. Stossel, a professor of medicine at Harvard Medical School who is familiar with the new research. "But the payday's a long way off," he cautioned.

The findings are in the March 23 issue of the journal Cell.

Platelets are tiny fragments that circulate in the blood. Humans are typically home to 150,000-200,000 platelets, which live about eight or nine days and help the circulatory system create blood clots that "plug holes" such as wounds, said Dr. Louis M. Katz, executive vice president for medical affairs for the America's Blood Centers organization and medical director of the Mississippi Valley Regional Blood Center in Davenport, Iowa.

Without enough platelets, people can suffer from uncontrollable bleeding. Transfusions are often necessary when people have cancer or undergo treatments for diseases such as leukemia and lymphoma. In those cases, treatment often destroys bone marrow, inhibiting platelet production.

Platelets also aren't very sturdy. While red blood cells can last several weeks in a refrigerator, platelets cannot be refrigerated, because the cold makes them vulnerable to immune system cells. But room-temperature storage leaves platelets open to bacterial attack, Katz said.

According to Katz, seven days is the current storage limit for platelets. "Managing the inventory is hard," he said. "It's easy to run out of platelets, because they last for such a short time on the shelf."

The result: Platelets often deteriorate and are wasted before anyone can use them. According to one estimate Stossel has seen, hundreds of millions of dollars of platelets go bad each year before they're needed.

In the new study, a team led by Dr. David Huang and Dr. Benjamin Kile of The Walter and Eliza Hall Institute of Medical Research conducted a genetic analysis of platelets to understand more about their life span.

They reported that platelets are essentially programmed to commit suicide. But, in experiments conducted with mice, they also found that they could genetically adjust the life span of the platelets.

"In theory, blocking function of some of the proteins made by these genes might prolong or shorten platelet survival," explained Stossel, who has also been working to understand the life span of platelets.

Longer-living platelets could mean more than benefits in terms of storage. They could also live longer in patients themselves, said Dr. Karin Hoffmeister, a professor of medicine at Harvard Medical School who has worked with Stossel.

"Longer-living platelets may mean less necessary transfusions. Assuming that platelets are cleared with a slower rate, more platelets would be circulating at a certain time, and fewer platelets would need to be transfused," she said. "Cancer patients, bone-marrow and liver transplant patients, as well as patients undergoing major surgery, would benefit from long-living platelets. The question remains if long -living platelets would also retain their function."

More information

Find out more about how blood products are used at the American Red Cross.

SOURCES: Thomas P. Stossel, M.D., professor, medicine, Harvard Medical School, Boston; Louis M. Katz, M.D., executive vice president for medical affairs, America's Blood Centers, and medical director, Mississippi Valley Regional Blood Center, Davenport, Iowa; Karin Hoffmeister, M.D., professor, medicine, Harvard Medical School, Boston; March 23, 2007, Cell
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