The Stem Cell

by Christopher Scott

The real estate saying, location, location, location, also applies to stem cells, which are most productive in their home environment, the niche. If the lungs, skin, and liver are “cities” of cells, the niche is the neighborhood within, the specific environment where stem cells can be found. The space deep inside the bone marrow is one example of a niche. Another is a swelling of cells along the hair follicle called the bulge (see the figure below, and the website of Rockefeller University’s Elaine Fuchs, a niche pioneer). And like any good neighborhood, the local environs provide services to ensure survival and protection. They also entice stem cells to stay put. Inside the niche, stem cells put their genes for specialization on hold.

How important is the niche? Things go badly without it.

An embryonic stem cell removed from the environs of the embryo and put into an adult mouse’s abdomen unleashes a torrent of unregulated activity and becomes a tumor. Put the embryonic cell back in its natural habitat and peace and happiness reigns, and the cell develops normally. Now, a team of Canadian scientists say they have unraveled some of the mystery of the embryonic niche, understanding more about how signals from the niche keep things under control. Figuring out the chemical checks and balances could become important in controlling tumor growth, leading to new therapies.

A fine example of the connections between adult and embryonic stem cell biology.