Fig. 10: Schematic diagram showing the role of Shh as a macrophage chemoattractant during regeneration of the gastric epithelium.

Shh, secreted from the gastric parietal cells in response to acute injury to the stomach induced macrophage chemotaxis and subsequently CD44v9-expressing SPEM. Shh acts as a macrophage chemoattractant via a smoothened-dependent mechanism. IL-33 is released from the injured epithelium, and macrophages drive the polarization of macrophages to an M2 phenotype. IL-13, released from recruited ILC2 cells, subsequently regulates the development of CD44v9-expressing SPEM, which is crucial for the regeneration of the gastric epithelium.