IL-7R signaling protects Rag⁻ mice from DSS-induced colitis.

<p>(<b>A, B</b>) WT (n = 4), Rag⁻ (n = 8), Rag⁻IL-7R⁻ (n = 7) and Rag⁻OT-I⁺ mice (n = 6) received dextran sulfate sodium (DSS) via the drinking water. From day 5 on, DSS-free drinking water was provided. (<b>A</b>) Body weight was determined every day and calculated in relation to the initial body weight. Shown are the mean relative body weight ± SEM and the time after onset of DSS treatment. (<b>B, C</b>) Colon samples were taken at day 8 and analyzed histologically. Shown are histological scores for groups of untreated (open symbols; n = 4) and DSS-treated mice (closed symbols; n = 6–8). (<b>C</b>) Shown are representative colon sections from the indicated mice. (<b>A–C</b>) Data represent one experiment.</p

IL-7R signaling promotes lymphopenia-associated IEC hyperplasia and alters colon function.

<p>(<b>A</b>) Colon sections from WT (n = 13–16), Rag⁻ (n = 16–37) and Rag⁻IL-7R⁻ mice (n = 13) were stained with DAPI and antibodies for Ki67, EpCam, cleaved caspase 3 (Casp3) or Gob5. (<b>B</b>) Colon wall thickness (µm) and (<b>C</b>) the percentage of Ki67⁺ cells in crypts were determined for WT (n = 6), Rag⁻ (n = 12) and Rag⁻IL-7R⁻ (n = 6) mice. (<b>B, C</b>) 30–60 individual measurements were performed. (<b>A–C</b>) Data are representative for 4 independent experiments and 2–3 staining reactions per mouse. (<b>D</b>) Transepithelial resistance (Ω·cm²), and apparent permeabilities (P) for (<b>E</b>) Na⁺ and (<b>F</b>) Cl⁻ were determined for colon samples from WT (n = 6), Rag⁻ (n = 5) and Rag⁻IL-7R⁻ (n = 5) mice. Five to twelve independent measurements per experimental group were performed. (<b>B–F</b>) Shown are mean values+SEM. Statistically significant values are indicated: ** p<0.01 and *** p<0.001 (Student's t test).</p

IL-7 promotes IEC proliferation and survival.

<p>(<b>A, B</b>) Rag⁻IL-7⁻ (IL-7⁻; n = 3) and Rag⁻IL-7R⁻ (IL-7R⁻; n = 3) mice were treated with PBS (white bars) or IL-7/anti-IL-7 (black bars) twice a week for 2 weeks. (<b>A, C</b>) Colon wall thickness (µm) and (<b>B, D</b>) the percentage of Ki67⁺ cells in crypts were determined in colon sections from (<b>A, B</b>) IL-7-treated Rag⁻IL-7⁻ and Rag⁻IL-7R⁻ mice and (<b>C, D</b>) untreated WT (n = 6) and IL-7tg (n = 5) mice. (<b>A</b>) 30–54, (<b>B</b>) 15–23, (<b>C</b>) 47–68 and (<b>D</b>) 29–32 individual measurements were performed per experimental group. Shown are mean values+SEM. Statistically significant values are indicated: * p<0.05 and ** p<0.01 (Student's t test). (<b>E</b>) Colon sections from PBS-treated (upper row) and IL-7/anti-IL-7-treated Rag⁻IL-7⁻ (lower row; n = 3) were stained with DAPI and antibodies for Ki67, EpCam, cleaved caspase 3 (Casp3) or β-catenin (βcat). (<b>F</b>) Colon sections from WT (n = 5) and IL-7tg mice (n = 6) were stained with DAPI and antibodies for β-catenin. (<b>E, F</b>) White arrows indicate nuclei. Bar diagrams show the percentage of luminal IEC with nuclear β-catenin. 130–280 nuclei per experimental group were counted. Shown are mean values+SEM. Statistically significant values are indicated: * p<0.05 and ** p<0.01 (Student's t test). (<b>A–F</b>) Data represent one experiment with a total of 23 individual mice and 2–3 independent staining reactions per mouse.</p

Elevated levels of IL-7 expression and IEC hyperplasia in the colon of Rag⁻ mice.

<p>(<b>A</b>) Representative bioluminescence (BL) images for Rag-competent (Rag⁺; n = 31) and Rag-deficient IL-7GCDL mice (Rag⁻; n = 21) are shown. BL was determined (<b>B</b>) in the intestine and (<b>C</b>) thymus, heart, lung, liver, skin and kidney of Rag⁺ (n = 12) and Rag⁻ IL-7GCDL mice (n = 12). (<b>A–C</b>) BL is shown in photons per s per cm² per steradian. (<b>D, E</b>) Colon sections from Rag⁺ (n = 5–8) and Rag⁻ IL-7GCDL mice (n = 6–8) were stained with (<b>D</b>) periodic acid-Schiff (PAS)/Alcian blue (AB) or (<b>E</b>) DAPI and antibodies for IL-7 and EpCam. (<b>D</b>) Differentiated goblet cells stain positive for PAS (red) and appear purple/magenta. Acidic mucopolysaccharides/glycosaminoglycans are visualized by AB. Arrows indicate the distance between the basis of the crypts and the colon lumen. (<b>D, E</b>) Data are representative for 3 independent experiments and 2–3 staining reactions per mouse.</p

IEC express functional IL-7R.

<p>(<b>A, B</b>) IEC were isolated from the colon of (<b>A</b>) Rag⁻IL-7R⁻ and (<b>A, B</b>) Rag⁻ mice. (<b>B</b>) Rag⁻ IEC were stimulated with 20 ng/ml rec. IL-7 for 15 minutes or were left untreated. The levels of IL-7R expression and Stat5 phosphorylation (p-Stat5) were determined by flow cytometry. (<b>A, B</b>) Shown are relative cell numbers and relative fluorescence intensities for (<b>A</b>) IL-7R and (<b>B</b>) p-Stat5 after gating on viable (<b>A</b>) (7AAD⁻), (<b>A, B</b>) CD45⁻, EpCam⁺ IEC. Results are representative for 2–3 independent experiments.</p