Because stem cells are different from normal cells, they require a special place to live within the body. This space is called the stem cell niche, which provides an environment that allows the stem cells to continually renew themselves and differentiate into other cells. The niche is important not only because it serves as a place for stem cells to live, but also because it supports them, enabling them to do much more. The niche helps the stem cells interact with other cells and the extracellular matrix (ECM) that surrounds the cells. ECM is made of proteins and proteoglycans (proteins+sugars in one molecule) which provide a structure that allows cells to grow and signals that tell cells what they should be doing.

 

​The interactions stem cells have with other cells and with the ECM help to direct the stem cells to do what the body needs them to do. This is important because the body’s needs change over time, and the stem cells need to be able to respond to these changes to help restore balance within the body. For example, when you get sick, your body needs more white blood cells to fight off the infection. Signals can be sent to the stem cells in the bone marrow, where hematopoietic stem cells live, to produce more white blood cells.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Because stem cell niches play such an important role in keeping stem cells alive and in the right state, issues with the stem cell niche can cause health problems. A niche that is damaged by age or disease might not give stem cells everything they need to grow right. This means that abnormal niches may consequently influence the function of stem cells within the niche. Stem cells that aren’t normal to begin with in an abnormal niche can also lead to diseases like cancer.

 

 

 

 

 

 

 

 

 

 

 

 

EXAMPLE LOCATIONS OF STEM CELL NICHES

• Hematopoietic Stem Cells: Bone marrow

Bone marrow is a dark red substance that makes up the inside of the bone. It provides a place for many different cells to grow, including hematopoietic stem cells. Red blood cells and white blood cells are produced from hematopoietic stem cells in the bone marrow.

 

 

 

 

 

 

 

 

 

 

 

 

• Neural Stem Cells: Subventricular zone

The ventricles are a part of the brain that is filled with fluid rather than tissue. The subventricular zone is an area of the brain made of tissue next to the ventricles. Neural stem cells live in the subventricular zone and can become neurons and glial cells.

 

 

 

 

 

 

 

 

 

 

 

 

 

• Muscle Stem Cells: Between basement membrane and muscle fibers

Muscles are made up of long, string-like structures called fibers that are formed through the fusion of muscle cells. Muscle stem cells are found in between these fibers and the basement membrane, a fibrous layer of extracellular matrix that lines the outside of the muscles. Muscle stem cells, also known as satellite cells, are able to move to places where damage has occurred in the muscle fibers and differentiate into muscle cells to repair the damage.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

• Intestinal Stem Cells: Intestinal crypts

At the bottom of folds in the intestines are areas protected from the rest of the intestine with special environments that contain niches called intestinal crypts. Intestinal stem cells differentiate in these crypts, pushing new cells out to the surface of the intestines to form new epithelium and keep up with the cells lost during digestion.

 

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• Hair follicle Stem Cells: Hair follicle bulge

Hair follicle stem cells live in the layer on the outer hair follicle bulge. The hair follicle is the living tissue on the side of a piece of hair under the skin. Hair follicle stem cells are able to generate new hair and form new skin near the location of the hair.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

How do we get stem cells?

Because stem cells can be used for research and regeneration, we want to be able to collect them so we can study them and use them outside of the body. To do that, we need to take some of them from the body. The main way we can do that is by taking them from the niche. For example, bone marrow can be collected from a living person by using a drill to get into a bone and sucking out some of the marrow. Because the bone marrow is the stem cell niche for hematopoietic stem cells, collecting bone marrow is also a way of collecting hematopoietic stem cells. However, some stem cell niches are harder to access. Another way of collecting bone marrow that doesn’t involve having to go through bone is by using drugs that get your body to produce more hematopoietic stem cells before dumping them into the blood. This allows doctors to filter your blood and get stem cells from your blood rather than your marrow.