Stem cells are immature cells that can develop into a variety of adult cells. In this case, hematopoietic stem cells can develop into all blood and immune system cell types and are already used therapeutically to restore the hematopoietic system of patients after chemotherapy or radiation therapy.
The new technique to identify hematopoietic stem cells (HSCs) will enable scientists to determine where stem cells are located in blood-forming tissues and to trace the developmental routes these stem cells take as they mature into blood cells. If the researchers' studies in mice apply to blood-forming stem cells in humans, the technique may enable safer transplants of stem cells, by improving purification of the stem cells prior to transplantation, said the scientists.
Sean J. Morrison, a Howard Hughes Medical Institute investigator at the University of Michigan, led the research team, which published its findings in the July 1, 2005, issue of the journal Cell. Other members of the team included graduate students Mark Kiel and Omer Yilmaz as well as postdoctoral fellow Toshihide Iwashita from the Morrison laboratory. Another co-author of the paper is from Harvard Medical School.
The method developed by Morrison and his colleagues can distinguish different types of blood-forming progenitors based on differences in their expression of members of a family of highly similar protein receptors, called SLAM family receptors. The receptors nestle in the surface of the cell membrane and detect external chemical signals and translate those signals into cellular responses.