Stem cells are undifferentiated cells with the potential to develop into many different types of cells in the body, they mainly serve as a repair system. In simple terms, they are the body's raw materials from which damaged tissue can be repaired. There are two types of stem cells: embryonic and adult stem cells. Currently, we have adult stem cells in our bone marrow, liver tissue and heart but did you know we also have stem cells in the epithelial lining of our intestines?
sourced from: https://www.nature.com/articles/s41575-018-0081-y
Intestinal stem cells are multipotent adult stem cells, which in mammals reside in the base of the crypts of the adult intestine. Intestinal stem cells continuously self-renew by dividing and differentiating into the specialized cells of the intestinal epithelium, which renew throughout life.
The inner layer of the intestines is coated with several cells with unique functions such as secreting mucus and enzymes or alerting the immune system when a pathogen has entered. This layer of cells is called the intestinal epithelium and it has many small indentations called crypts under which a small collection of stem cells can be found. As the cells on the epithelium wear out (every 5 days), the stem cells specialize and replace them. These epithelial stem cells are not pluripotent like embryonic cells meaning they can only specialize to form epithelial cells.
Stem cells provide endless opportunities for us such as for therapeutic purposes such as treating gastrointestinal disorders like inflammatory bowel disease (IBD). Studies done on animals show that intestinal stem cells delivered to the gut can attach to ulcers and help regenerate healthy tissue and if we produce goblet cells (which help control the immune response to proteins found in food) from these stem cells we can study food allergies.
So what has been stopping us from finding these cures and treatments? Well, these stem cells only remain immature (undifferentiated/ unspecialised) when in contact with Paneth cells (highly specialized secretory epithelial cells located in the small intestinal crypts of Lieberkühn which support the stem cells). Paneth cells control stem cells through 2 main signalling pathways: Notch and Wnt, which coordinate cell proliferation, especially during embryonic development. In 2013 Harvard and MIT researchers led by the Harvard Stem Cell Institute found a way to grow these stem cells by replacing the Paneth cells with small molecules (valproic acid and CHIR-99021) that promote the proliferation of the epithelial stem cells. Furthermore, they say that stem cells grown in lab dishes with these molecules will stay immature indefinitely; by adding other molecules such as inhibitors that influence the Wnt and Notch pathways researchers can control what type of cell they eventually become. Researchers are now creating intestinal tissues for transplant and developing rapid methods for testing drugs' effects on intestinal cells.
There is a lot we don’t know about stem cells but with this discovery, scientists are looking into creating many new therapies and trying to understand the workings of stem cells for applications throughout the body.
For those who want to dig into the science of this, check out the research papers attached below!
Written By: Sakshi Deshpande
Glossary
Specialization of cells: when some of the genes in a cell turn off so the cell turns into one kind of cell in the body. For example, a stem cell turns off some of its genes and now can only produce keratin (so it's a hair cell)
Bibliography
Trafton, A. (2013, December 7). Harvard and MIT researchers unlock new means of growing intestinal stem cells. Harvard Stem Cell Institute (HSCI). Retrieved June 20, 2022, from https://hsci.harvard.edu/news/harvard-and-mit-researchers-unlock-new-means-growing-intestinal-stem-cells
Umar, S. (2011, October 1). Intestinal stem cells. Current gastroenterology reports. Retrieved June 20, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2965634/
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