Many specialized cells, such as in the skin, intestinal mucosa or blood, have a lifespan of only a few days. For these tissues to function, a steady replenishment of specialized cells is indispensable. This is the task of so-called "adult" stem cells also known as tissue stem cells.
Stem cells have two main characteristics: First, they are able to differentiate into all the different cell types that make up their respective tissue a property called pluripotency. Second, they need to renew themselves in order to be able to supply new specialized tissue cells throughout life. These processes have best been studied in mouse bone marrow.
Up to now, scientists have assumed that adult stem cells have a low division rate. According to theory, they thus protect their DNA from mutations, which happen particularly during cell division and can lead to transformation into tumor stem cells. However, the actual number of divisions of a blood stem cell throughout an organism's lifespan has remained unknown.
Professor Dr. Andreas Trumpp and Dr. Anne Wilson have now discovered a group of stem cells in mouse bone marrow that remain in a kind of dormancy almost throughout life. Trumpp, who has been head of the Cell Biology Division at DKFZ since summer 2008, had carried out these studies at the Ecole Polytechnique Fdrale in Lausanne, Switzerland, jointly with colleagues at the Ludwig Institute for Cancer Research located in the same city.
The scientists labeled the genetic material of all mouse blood cells and subsequently investigated how long this label is retained. With each division, the genetic material is apportioned to the daughter cells and, thus, the labeling dilutes. During these studies, the investigators discovered the dormant stem cells which divide only about five times throughout the life of a mouse. Translated to humans, this would correspond to only one cell division in 18 years. Most of the time, these cells, which con
|Contact: Dr. Sibylle Kohlstaedt|
Helmholtz Association of German Research Centres