Figure 3. Activation of the tuft cell – ILC2 circuit drives small intestine lengthening.

(A) Small intestine (SI) length in RR, A20^flRR, Il25^−/−A20^flRR, Il4ra^−/−A20^flRR and Pou2f3^−/−A20^flRR mice. (B–E) SI length in (B) wild type, (C) C57BL/6 GF, (D) Il4ra^−/− and (E) Pou2f3^−/− mice after 4 weeks of serial treatment with rIL-25. (F) SI length of mice 5 weeks after hydrodynamic gene delivery with IL-13 or hIgG1 control plasmid. (G) SI length of mice treated with rIL-4 complexes for 4 weeks. (H) Cytospins stained with H&E. Micrographs show representative images of Tritrichomonas isolated from cecum of mice housed in UCSF vivarium. Scale bars; 20 μm. (I and J) Wild type (WT) mice were colonized with purified Tritrichomonas at 3 weeks of age. (I) SI length measured 8 weeks later and compared to age-matched Pou2f3^−/− mice naturally colonized with Tritrichomonas. (J) SI length of wild type mice in (I) plotted against tuft cell frequency. (K) SI length in wild type mice 28 days after infection with H. polygyrus (H.p.). (L and M) Crypt fission in the proximal SI in Lgr5-CreERT2-EGFP x R26R-Confetti mice as described in methods. (L) Representive images from mice 28 days after infection with H. polygyrus. Lgr5 stem cells are pseudocolored in dim yellow (Lgr5-CreERT2-EGFP) and clonal crypts are randomly marked with bright yellow (YFP), red (RFP) or blue (CFP), driven from the R26R-Confetti locus. (M) Quantification of crypt fission of mice as in (L), or after 4 weeks of serial treatment with rIL-25. Scale bars; 200 μm. Data pooled from multiple independent experiments (A, C, D, F, M) or from one experiment representative of at least two independent experiments (B, E, G–I, L). (L, mean and s.e.m, n = 6–11). **p < 0.01, ***p < 0.001, ****p < 0.0001; ns, not significant by Mann-Whitney U or one-way ANOVA.