July 1, 2005 — Finding stem cells in a body made from trillions of other cells has proven to be a slow and arduous process, but scientists have discovered that at least some stem cells possess barcode-type markers that let them stand out and be counted.

While the process is not quite as simple as swiping a grocery item over a barcode reader, it is faster and more reliable than current stem cell detection methods, which require that scientists locate 10 to 12 certain proteins within the cells, stain the proteins individually and then make an educated decision.

Thanks to a newly identified family of blood genes called SLAM, "Now it's like looking for a woman wearing a red top but not a green dress," said Sean Morrison, who led the study.

Morrison, a researcher at the Howard Hughes Medical Institute and an associate professor of internal medicine at the University of Michigan Medical School, explained that SLAM genes either express certain cell surface receptor proteins or not. If they do not, scientists still can detect the negative expression and read it as part of the cell's "barcode."

The key to unlocking blood stem cell barcodes was to determine which SLAM proteins are associated with stem cells and which are not. Morrison and his team did this by giving laboratory mice doses of the various SLAM proteins and analyzing how the proteins affected the rodents.

Findings are published in the latest issue of Cell.

While study results only are conclusive for mice cells, Morrison believes human blood stem cells likely will possess comparable markers. Stem cells are primitive cells that have the ability both to grow into specific blood cells.

"We should know if humans have these markers in about a year's time," he told Discovery News. "Tests involving patients undergoing bone marrow transplants should follow soon afterwards, and could lead to safer, more effective drugs and treatments."

These therapies could be used to treat sickle cell anemia, leukemia and other blood disorders. If markers lead to the discovery of additional types of stem cells, new treatments for many forms of cancer may become available in the not-too-distant future.

Amy Wavers, a stem cell specialist at Harvard's Joslin Diabetes Center, told Discovery News that she welcomed the barcode method for identifying blood stem cells because it is "simple and broadly applicable."

She said, "The new method allows us to look at stem cells in their native environment, which is in actual tissue cells. It is also a big advance because we now have a greater chance of obtaining more pure stem cell grafts (samples)."

Wavers explained that patients undergoing bone marrow transplants currently receive a mixture of cells, some of which may or may not be stem cells. The easier identification method will tell doctors if enough stem cells are present to warrant the transplant.

Morrison said these identifications could be a life or death matter, as for cancer patients who have blood removed and frozen before chemotherapy. Chemo kills cancer cells but also can damage healthy blood cells in the process. When patients receive their blood back after chemotherapy, sometimes doctors miss detecting cancer cells within the blood and the person is subjected to cancer again.

"It is really important that we purify the frozen stored blood, and the new method will dramatically enhance our ability to do this," he said.