First Stem Cells Purified from Marrow

Article excerpt

First stem cells purified from marrow

Scientists knew where to search, but trying to find stem cells in the bone marrow was like looking for a toothpick in a lumberyard. Though they give rise to the entire blood supply and immune system, stem cells make up only a small fraction of bone marrow cells (0.05 percent in the mouse), and scientists have had only indirect evidence that they exist at all. Now, researchers using refined immunological procedures on mouse bone marrow have succeeded in purifying stem cells for the first time, they report in the July 1 SCIENCE. Similar procedures in humans, though more difficult, might prove helpful in isolating human stem cells and could improve the efficiency and safety of bone marrow transplantation, they add.

Before performing a marrow transplant, doctors check to see that the antigens of the donor's bone marrow closely match those of the recipient's. A mismatch could make the host's immune system reject the donor cells. Since stem cells are only precursors and thus have no antigens that the patient's immune system would recognize as foreign, a stem cell transplantation theoretically would avoid the risk of adverse immune reactions. For this reason, the goal of isolating a pure stem cell population has enticed medical researchers for decades.

To obtain mouse stem cells, Irving Weissman and Shelly Heimfeld of Stanford University School of Medicine in Palo Alto, Calif., and Gerald Spangrude, now at the Royal Melbourne Hospital in Victoria, Australia, sorted types of mouse bone marrow cells by the different antigens on their surfaces. …