- A new reservoir of stem cells have been discovered in the intestine which are quiescent (dormant) in nature and do not proliferate.
- These passive cells are activated when needed and have the capacity to produce any kind of intestinal cell.
- Quiescent cells are important for tissue regeneration and for participation in tumor development.
A new group of stem cells have been discovered in the intestine which have very different characteristics to those of the abundant and active stem cells already known in this organ.
These new group of stem cells in the intestine that are quiescent, which means they do not proliferate and are apparently dormant.
‘Quiescent cells play an important role of tissue regeneration in situations of stress, like after chemotherapy, in inflammatory processes, and in tissue infections.’
The rate of cellular regeneration in the intestine is higher due to the wear and tear originated by its function degrading and absorbing nutrients and eliminating waste. As a result the entire cell wall is renewed once a week.
This explains why the intestine holds a large number of stem cells in constant division, thereby producing new cell populations of the various types present in this organ.
The discovery was made by researchers at the Institute for Research in Biomedicine (IRB Barcelona) headed by ICREA investigator Eduard Batlle, head of the Colorectal Cancer Laboratory.
Reservoir of Stem Cells
These reservoir of stem cells are found in the ratio of one quiescent cell for every 10 active intestinal stem cells.
They have no apparent function in healthy conditions. But they play an important role in situations of stress, like after chemotherapy, in inflammatory processes, and in tissue infections, in all conditions in which the population of "normal/active" stem cells is depleted.
These cells serve to regenerate the organ by:
- giving rise to the various types of cells present in the intestine
- renewing the population of "normal/active" stem cells
- restoring balance to the tissue
"In intestinal cell hierarchy, there are no cells above others, so the two populations are in a continual balance to ensure the proper function of the organ," Eduard Batlle explains.
Role of Cells in Tumor Development
The cells that are dividing in the tissues are affected by drugs against cancer.
"Because quiescent stem cells divide infrequently, they are resistant to many types of chemotherapy and they regenerate the tissue that this treatment has damaged," explains Eduard Batlle, head of one of the labs of international prestige in research into intestinal stem cells and their involvement in colorectal cancer.
After chemotherapy, these cells change their behavior, become active and regenerate all cell types in the intestine.
Though quiescent cells are present in many kinds of tissue and they help in tissue regeneration, increasing evidence points to their involvement in tumor development.
"It is difficult to study these cells, mainly because they are scarce and there are technical limitations with respect to monitoring, straining and distinguishing them from the others," explains Francisco Barriga, first author of the study and current postdoctoral fellow at the Memorial Sloan Kettering Cancer Center in New York.
Using advanced techniques, the group has identified the distinct genetic program used by quiescent stem cells with respect to normal intestinal ones.
This cell population has been labeled with a specific marker, the Mex3a protein, which has allowed them to track it over time. "We intend to continue studying quiescent stem cells in health and disease and to discover the function of the genes that distinguish them in the colon and in other organs," says Batlle.
The study has been published in Cell Stem Cell
- Francisco Barriga et al. Mex3a marks a slowly dividing subpopulation of Lgr5+ intestinal stem cells Cell Stem Cell . Cell Stem Cell>; (2017) doi: 10.1016/j.stem.2017.02.007