Fig. 4: Aberrant pan-epithelial Grem1 expression causes intercompartmental remodelling with de-repression of stem cell supporting fibroblast cells.

A p-Smad1, 5 immunohistochemistry shows physiological villus epithelial cell nuclear staining from the crypt isthmus upwards (brown stain). Pan-epithelial expression loss is seen in Vil1-Grem1 mice, with little reversion of epithelial stain seen following 10 weeks UCB Ab7326 therapy. Automated stain quantification using digital pathology platform used to exclude stromal cell staining (QuPath) (n = 3 per group, >15 villi or polyps total). B p-Smad1,5 immunohistochemistry shows physiological stromal cell staining in the villus stomal compartment (brown stain). Loss of expression is seen in untreated Vil1-Grem1 animals as a consequence of intercompartmental BMP antagonism. Treatment with UCB Ab7326 recovers stromal expression levels of p-Smad1,5 in treated Vil1-Grem1 mice. Automated stain quantification using digital pathology platform used to exclude epithelial cell staining (QuPath, n = 3 per group, >15 villi or polyps total). C Hi-plex in situ hybridization (12 markers) was used to identify and topographically map functionally distinct fibroblast subtypes (SEMF, Cd55(+) Wnt2b(+), and Trophocytes) in wildtype and Vil1-Grem1 mouse tissue. Image analysis software was used to identify each subtype and map cell location back onto the tissue based on density distribution (coloured circles, within shaded areas - HALO, Indica Labs) (n = 5 mice per group, ≥10 villi, crypts or polyps total, one way ANOVA with Dunnett post-hoc corrections, p values as stated). Data were ±s.e.m. Scale bars 200 µm. Source data are provided as a Source Data file.