What Does the Concept of the Stem Cell Niche Really Mean Today?

The concept of the stem cell niche had evolved significantly by 2012, reflecting advances in cell visualization, monitoring, and manipulation. Researchers highlighted that niches could be composed of various cell types and extracellular structures, and they might produce factors like Notch, Wnt, FGF, EGF, TGF-β, SCF, and chemokines to regulate stem cell functions. Three main roles of niches were proposed: providing special support for stem cell viability, acting as feedback control systems to regulate stem cell pools, and coordinating interactions among different tissue compartments. The hair follicle niche was cited as an example of the latter, where multiple cell types interact closely to maintain tissue homeostasis.