Figure 4.

The niche and asymmetric cell division of stem cells. The fate of stem cells is determined by their interaction with their microenvironment or niche. The niche is composed of other (stromal) cells, extracellular matrix (ECM), and signaling factors, which, in combination with intrinsic characteristics of stem cells, define their properties and potential. Adult stem cells divide asymmetrically to produce two kinds of daughter cells. Whereas one remains in the niche as a self-renewing stem cell, the other one becomes a precursor or progenitor cell, exits the niche, and enters a pathway of proliferation and differentiation, which leads to the formation of a mature cell type.