New stem cell mechanisms in your gut: Stem cells in your gut are controlled by newly discovered biophysical mechanisms - Azi Berita News

Your gut is an amazing place. The special layer of cells that line the inside of your small and large intestines take nutrients and water from what you eat while keeping anything bad out of your system. This layer is called the intestinal epithelium. It actually renews itself every four to seven days using stem cells. These are special types of cells that can self-renew by dividing and differentiating to produce other types of cells to renew your organs. Scientists still don’t know how exactly they make this decision, or what defines stem cells.

Bernat Corominas-Murtra, formerly a postdoc at the Austrian Institute of Science and Technology (ISTA) and now an assistant professor at the University of Graz, and Edouard Hannezo, professor at ISTA, in collaboration with an international experimental research group led by Jacco Van Tim Rheenen in Amsterdam studied cells stems in the intestinal epithelium. They discovered an exciting new mechanism that could change our understanding of what stem cells are. Their findings have now been published in the journal Natural.

The intestinal epithelium is just one thick layer of cells and is constantly being renewed. It is present all over the villi which look like tiny tentacles that cover the inside of the small and large intestines. Between the villi, there are small pockets of tissue called intestinal crypts. The name might pose some mystery and it might not be too far off from what really happened there. “At the bottom of the crypts, the stem cells in the epithelium continue to divide. Some of the resulting cells remain as stem cells in the crypt and others are pushed outwards towards the ends of the surrounding villi, “Corominas-Murtra explains,” there, ultimately, they differentiate into functional cell types that allow gut function and which discarded after a few days. This happens all the time in your body and if this mechanism breaks down, you can have serious medical problems.”

When studying these stem cells in the small and large intestines, scientists were at first confused. “How we usually think of stem cells is that being a stem cell is determined by the intrinsic biochemical properties of the cell — something like a biochemical marker that we can identify,” continued Corominas-Murtra. “We found that among the cells that had these traditional stem cell markers, many of them never actually worked as stem cells but were pushed out of the basement for disposal, without contributing at all to long-term gut renewal. We also saw that while the classical markers estimated the same number of stem cells in the small and large intestine, there were about twice as many of them actually working as stem cells in the small intestine than in the large intestine.” The scientists therefore wanted to understand what determines which cells actually act as stem cells and they discovered a surprising new mechanism that regulates stem cells in the basement.

“We found that whether these cells behave as stem cells or not, it’s all about their location! Cells in the epithelium are not only pushed out of the basement by cell division beneath them – as in a conveyor belt – but there are other types of movement involved,” Corominas-Murtra explains. The scientists found that the cells in the epithelial lining are also actively moving in random directions — back and forth along the conveyor belt if you will. In this way, cells that had been pushed along the conveyor belt for a while can end up back at the bottom of the basement, and act there again as stem cells to divide and repopulate the epithelium. Edouard Hannezo explains the possible implications of these findings, “This movement represents a novel environmental mechanism that determines which cells serve as stem cells. In the small intestine, the molecular signals that regulate movement are stronger than in the large intestine, so cells can move more frequently back into the basement. This explains why there are more stem cells at work in the small intestine than in the large intestine. This could have major implications for our understanding of what stem cells really are and how to use them in medical applications.”

These insights build on previous research by Bernat Corominas-Murtra and Edouard Hannezo at ISTA and the work of the Van Rheenen group. Originally from a physics background, Corominas-Murtra and Hannezo created an advanced mathematical model of the intestinal epithelial lining that includes the movement of cells both away from and back into the basement. Using their model, they were able to predict the number of actually functioning stem cells in the small and large intestines. A number of other research groups from across Europe designed experiments using the latest methods in microscopy and genetics to test the predictions and found that they were accurate. They even tried to block chemical signals in the basement and saw that this reduced the number of stem cells working as expected.

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Material provided by Austrian Institute of Science and Technology. Note: Content can be edited for style and length.

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