Fig. 2: AHR expression on the the intestinal epithelium is required for protection against NEC.

a, b, d, e, g, h Representative confocal images and quantification of fluorescent intensity of AHR immuno-stained ileal sections of human (a, b, n = 7, 10 ileal section, p < 0.0001), mouse (d, e, n = 5, 5 ileal section, p = 0.0025), piglet (g, h, n = 7, 6 ileal section, p = 0.0004) ileal specimens from control (Ctrl) and NEC patients or animals. AHR, green signal; nuclei (DAPI, blue signal). c, f, i Expression of Ahr by qRT-PCR in the small intestine of human (c, n = 15, 9 human specimens, p = 0.0019), mouse (f, n = 8, 9 mice, p < 0.0001), and piglets (i, n = 5, 5 piglets, p = 0.0010). j H&E-stained representative images showing abnormal NEC histology in mice induced to develop experimental NEC in wild-type (WT), AHR knockout (Ahr^-/-), AHR intestinal epithelial cells knockout (Ahr^ΔIEC), and AHR myeloid knockout (Ahr^Δlys) mice. k Quantification of NEC severity (n = 7, 7, 7, 7, 7 mice, WT Ctrl vs WT NEC, p < 0.0001, WT NEC vs Ahr^-/- NEC p = 0.0074, WT NEC vs Ahr^ΔIEC NEC p = 0.0074, Ahr^-/- NEC vs Ahr^Δlys NEC p = 0.0001, Ahr^ΔIEC NEC vs Ahr^Δlys NEC p = 0.0001)^. l, m qRT-PCR expression of Il6 (l, n = 6, 14, 7, 9, 8 mice, WT Ctrl vs WT NEC, p = 0.0048, WT NEC vs Ahr^-/- NEC p = 0.0006, WT NEC vs Ahr^ΔIEC NEC p = 0.0268, Ahr^-/- NEC vs Ahr^Δlys NEC p = 0.0009, Ahr^ΔIEC NEC vs Ahr^Δlys NEC p = 0.0415) and Tnf-α (m, n = 6, 14, 7, 9, 8 mice, WT Ctrl vs WT NEC, p = 0.0350, WT NEC vs Ahr^-/- NEC p = 0.0012, WT NEC vs Ahr^ΔIEC NEC p = 0.0076, Ahr^-/- NEC vs Ahr^Δlys NEC p = 0.0473) in the intestinal epithelium. Scale bars in a, d, g, 50 μm. Scale bars in j, 100 μm. All data are presented as mean values ±  SEM. *p < 0.05, **p < 0.01, ***p < 0.001, p values obtained either from two-sided t tests or one-way ANOVA followed by multiple comparisons. Each dot in graphs represents data from an individual ileal section, human specimen, mouse, or piglet.