Stem cells are the most crucial cells in our body as they give rise to all other types of cells. The two hallmarks of a stem cell are the ability to self-renew (to produce similar cells) and being multipotent, which is the potential to develop into other kinds of cells.
Haematopoietic (blood) stem cells were the first cells to be identified as stem cells in the human body. It has been believed that there is about 1 stem cell in every 10, 000 bone marrow cells. Out of these stem cells, only a very small population of cells was believed to be involved in the self-renewal process, giving rise to new daughter stem cells.
Scientists from the German Cancer Research Center (DKFZ) have developed a new model to analyse the differentiation of blood stem cells within living organisms. So far, stem cells have only been able to be observed in cell cultures or by transplanting them into mice. By fusing a yellow-fluorescent-protein gene into a reporter protein, these stem cells in living mice can be visualised when it is switched on.
“A problem with almost all research on hematopoiesis in past decades is that it has been restricted to experiments in culture or using transplantation into mice,” says Professor Hans-Reimer Rodewald from the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ). “We have now developed the first model where we can observe the development of a stem cell into a mature blood cell in a living organism.”
By accompanying this method with a mathematical model, the scientists have found that there are more hematopoietic stem cells (~5000 cells) involved in producing differentiated cell types than previously thought to be. Although it was generally understood that the in-vitro culturing processes cause stem cell death, this study has shown that the cells derived from cell cultures are a very small subset of the larger population of stem cells in the living organism.
Dr. Katrin Busch from Rodewald’s team developed genetically modified mice by introducing a protein into their blood stem cells that sends out a yellow fluorescent signal. This fluorescent marker can be turned on at any time by administering a specific reagent to the animal. Correspondingly, all daughter cells that arise from a cell containing the marker also send out a light signal.
It is hoped that this new model would be more suitable to investigating the impact of harmful pathogens which target formation of different cell types, especially in leukaemia (blood cancer) and bone marrow transplantations.
The publication can be accessed here.