How are complex organs formed and maintained?
Stem cells are crucial for organ formation and maintenance
Complex organs, like the liver or our stomach are formed and maintained by so-called stem cells; cells which may repeatedly divide and with progeny being able to differentiate into the final cell type needed at the particular place. Divisions of stem cells have to be tightly regulated, both in space and in time, to generate correct organ morphology. How are such complicated patterns of regulation achieved? How do stem cell know at which place they are expected to divide how often?
Stem cells from the hair follicle as a model to study regulation
To study such questions Chacon-Martinez and colleagues developed an artificial system for culturing stem cells from mouse hair follicles. Each hair follicle contains a number of stem cells active in a tightly regulated way depending on its position in the follicle. Chacon-Martinez succeeded in culturing such cells outside the mouse body, i.e., mimicking conditions within a hair follicle closely enough to maintain stem cell’s activity. This „mimicking“ refers in particular to providing a 3D matrix and a number of soluble growth factors.
The cellular environment is crucial for stem cell activity
Using the culture system established Chacon-Martinez and colleagues could also transform normal epidermal cells into hair follicle stem cells. This reflects an observation made in real hair follicle: It is rather a cell’s environment than its history which makes it a stem cell or prevents it from dividing.