ABSTRACT
In this chapter, the authors describe what is known about the environment of a stem cell and the extent to which these are similar or differ for individual stem cell types. Despite the detailed description of the stem cell niche theory, Raymond Schofield had no clear evidence that this was the case, but research since then on a wide variety of stem cell scenarios in tissues from plants and animals, and ranging from the most primitive invertebrates to humans, has fully supported his vision. The model organisms used in studying stem cell niches have also generally had the added advantage of being amenable to genetic manipulation, enabling the roles of specific molecular components of the niche to be investigated. The stem cell niche can be composed of a wide range of cell and non-cell components, including secreted factors, extracellular matrix, physical factors, and nutrients and small molecules.
