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. 2023 May 9;11:1189225. doi: 10.3389/fbioe.2023.1189225

FIGURE 2.

FIGURE 2

Cell turnover and proliferation in the intestinal epithelium. Resident SCs, dispersed at the crypt base among Paneth cells, double each day. Maintenance of the stem status depends upon the exposure of SCs to a Wnt signal released by Paneth cells. The Wnt signal also induces the crypt surrounding stroma to release R-spondin, Delta-ligand and other factors that stimulate SCs to exit quiescence. When SCs divide, they generate both new SCs and TACs. Notch-Delta signaling in combination with Wnt control proliferation and differentiation of TACs. Hedgehog signals are secreted by proliferating intestinal cells, stimulate surrounding mesenchyme to release BMPs and to block TAC proliferation favoring their differentiation. Nogging produced at the crypt base prevent the BMP action on the crypt cells allowing SC and TAC proliferation to continue (modification of figure templates created with BioRender.com).