Wnt-expressing cells in the intestines: guides for tissue remodeling.

The crypt is a minimal functional unit in the intestinal epithelium. This unique structure is maintained by surrounding mesenchymal cells that focally interact with associated epithelial cells. Canonical and non-canonical Wnt ligands enable specific microenvironments localized to each end of the crypt major axis. While canonical Wnt-expressing cells are localized near the crypt bottom where intestinal stem cells reside, non-canonical Wnt-expressing cells are positioned beneath the luminal surface of epithelial cells. During wound healing, propagation and appropriate relocation of each cell population are thought to ensure subsequent crypt regeneration. In this review, I integrate information from recent studies on Wnt-expressing cells and intestinal fibroblast lineages and discuss their roles in homeostasis and wound healing. More information on the lineages of Wnt-expressing cells will help clarify the mechanisms of epithelial tissue formation.