(A) Adar1^fl/fl Mist1^Cre-ERT/+ mice were either mock-infected or infected with H. pylori (Hp) for 10 months to induce metaplasia, followed by 7 days of either vehicle or low-dose tamoxifen (LD-Tam) treatment to induce Cre-mediated deletion of Adar1 from chief cells. Mice were euthanized 4 days later. (B) During chronic H. pylori infection, Adar1-deficient chief cells (bottom) acquire metaplastic changes similar to chronically infected Adar1-sufficient chief cells (middle). Representative metaplastic gland bases (right panels) are shown. Scale bars, 50 μm (left panels), 10 μm (right panels). (C) Adar1-deficient chief cells show decreased Ki-67 staining following H. pylori infection (bottom), compared with chronically infected Adar1-sufficient chief cells (top). Representative gland bases (right panels) are shown. Scale bars, 50 μm (left panels), 5 μm (right panels). For B and C, images are representative of 2 mice per experimental treatment. (D) The distributions of Ki-67–positive cells at the gland base following H. pylori infection of mice with Adar1-sufficient (blue) or -deficient (red) chief cells are shown. Each data point represents a randomly selected field. No significant difference was seen between the distributions of H. pylori–infected mice with Adar1-deficient chief cells, but all H. pylori–infected mice with Adar1-deficient chief cells had significantly fewer Ki-67–positive cells at the gland base compared with H. pylori–infected mice with Adar1-sufficient chief cells. Few, if any, Ki-67–positive chief cells could be appreciated in mock-infected mice with Adar1-deficient chief cells, and this number was not determined. P values were calculated by 1-way ANOVA using Tukey’s multiple comparisons test. A statistically significant difference (P = 0.0022) was also found between H. pylori-infected, Adar1-sufficient and -deficient mice by Mann-Whitney test.