Fig. 7. Troy⁺ chief/stem cells activated by depletion of cycling isthmus cells.

(A–F) 5-FU treatment ablates proliferating cells in the isthmus. Control (A, B, C) and 5-FU treated (D, E, F) mice analyzed for Ki-67 (A, D, for proliferating cells), GFP (B, E, for Troy⁺ cells), and cleaved caspase 3 (C, F, for apoptotic cells). 5-FU induces apoptosis of cycling isthmus cells. (G–H) Accelerated expansion of Troy initiated lineage tracing upon tissue damage. Control (G) and 5-FU treated (H) mice were analyzed 1 month p.i.. Representative examples of Troy tracings (i, ii) and whole mount pictures from the gastric lumen (iii). Circles indicate LacZ⁺ glands reaching the lumen. (I) The number of tracings that reach the lumen was counted one month p.i. in 5-FU treated vs. untreated mice and shows a 6-fold increase (p<0.0001, t-test). Data are represented as mean +/− SEM of ten sections. (J) The number of LacZ⁺ cells in 100 tracing clones counted 1 month after 5-FU treatment. Percentage of clones with one, two or more than two cells is represented. (K) Time scheme of 5-FU experiment. Troy⁺ cells were labeled on day 0 by tamoxifen induction. Proliferative cells were subsequently ablated by 5-FU treatment three days later and tissues analyzed at 1 month p.i.