Intestinal Stem Cell Niche: The Extracellular Matrix and Cellular Components

Figure 1

The intestinal stem cell niche. The intestinal epithelium comprises a monolayer of polarised columnar cells organised along the crypt-villus axis. Intestinal stem cells reside at the base of the crypts and continuously generate transit-amplifying (TA) daughter cells that differentiate into various mature cells in the villi (enterocytes, goblet cells, enteroendocrine cells, tuft cells, or Paneth cells). The crypt surrounding microenvironment is made up of both physical/structural and cellular niche to regulate ISC homeostasis. The physical niche includes collagen fibres, integrins, fibronectin filaments, laminins, and glycosaminoglycan, which form a highly structured network named as the extracellular matrix (ECM). The cellular niche includes pericryptal myofibroblasts, fibroblasts, endothelial cells, neural cells, and smooth muscle cells. The ECM and cellular niche interact and communicate with each other via different signalling pathways such as the Wnt, Notch, TGF-β/BMP, Eph/ephrin, and Hedgehog pathways for stem cell maintenance.