Figure 4.

Plasticity in tissues with fast and slow turnover

(A) Waddington landscape of the intestinal crypt in homeostasis (left) and upon damage to the stem cell compartment (right). In homeostasis, cells gradually commit and differentiate while leaving the stem cell zone and losing access to stem cell niche factors. Yet, during damage and loss of stem cells, the majority of crypt cells can readily reverse their commitment due to permissive chromatin when exposed to stem cell signals. Stem cells at the “edge” of the stem cell niche (numbers indicate the cell position counting from the bottom of the crypt) are more likely to lose access to key stem cell signals and differentiate.

(B) Examples of tissues that employ self-replicating mature cells to sustain tissue renewal. In the damaged pancreatic acini, acinar cells can increase self-renewal and induce an accelerated rate of acini fission. Damage to the liver causes the emergence of oval cells from cholangiocytes that can both generate both new cholangiocytes as well as hepatocytes. Chief cells at the bottom of the stomach glands can self-replicate during homeostasis to sustain their pool, but damage endows these cells with expanded lineage potential.