However, in an emergency such as an injury of the bone marrow or if the messenger substance G-CSF is released, the dormant cell population awakes. Once awakened, it shows the highest potential for self-renewal ever to be observed in stem cells. If transplanted into irradiated mice, these cells replace the destroyed bone marrow and restore the whole hematopoietic system. It is possible to isolate new dormant stem cells from the transplanted animals and these cells are able to replace bone marrow again this can be done several times in a row. The situation is different with "active" stem cells, where bone marrow replacement can successfully be carried out only once.
"We believe that the sleeping stem cells play almost no role in a healthy organism," Trumpp explains. "The body keeps its most potent stem cells as a secret reserve for emergencies and hides them in caves in the bone marrow, also called niches. If the bone marrow is damaged, they immediately start dividing daily, because new blood cells are needed quickly." Once the original cell count is restored and the bone marrow is repaired, these stem cells go back to deep sleep. The larger population of "active" stem cells, however, keeps up the physiological balance of blood cells in the normal healthy state.
Andreas Trumpp expects that these results may give valuable impetus to our understanding of cancer stem cells: "Cancer stem cells, too, probably remain in a dormant state most of the time we think that this is one of the reasons why they are resistant to many kinds of chemotherapy that target rapidly growing cells. If we were able to wake up these sleepers before a patient receives treatment, it might be possible to also eliminate cancer stem ce
|Contact: Dr. Sibylle Kohlstaedt|
Helmholtz Association of German Research Centres