Antibiotic treatment of in vitro fetal organoids induces differentiation of Paneth cells and enteroendocrine cells. (A) Real-time qPCR analysis and (B) immunohistochemistry of innate defense marker Lyz1/LYZ1 in distal fetal organoids. Relative expression to reference genes Rpl32 and TbP. Black arrowheads indicate Paneth cells positively stained for LYZ1 and white arrows indicate Paneth cells not stained for LYZ1. Scale bars: 50 μm. Real-time qPCR analysis of (C) innate defense markers Reg3β and Reg3ɣ in distal fetal organoids and (D) (trans)epithelial sensing markers Gip, Nts, Gcg, Pyy, Sst, Sct, and Cck in proximal fetal organoids. Relative expression to reference genes Rpl32 and TbP. (E) Immunofluorescence of whole proximal fetal organoids for GIP and quantification of the amount of GIP-positive cells per organoid area. Statistical analysis was performed by (A, C, and D) 2-way analysis of variance with the Sidak multiple comparisons test or (E) 2-tailed unpaired t test. Error bars indicate means ± SD. Levels of significance are indicated: ∗P < .05, ∗∗P < .01, ∗∗∗P < .001, ∗∗∗∗P < .0001. (A, C, and D) n = 3 individual wells from a representative organoid culture of 4–6 independent cultures and (G) n = 40 organoids of 2 independent cultures.