Mesenchymal WNT2B is required for the development and function of the human intestine

Diarrhea-9 (DIAR9) is a severe congenital condition characterized by intractable diarrhea and malabsorption, linked to mutations in the WNT2B gene. Previous attempts to model this disease in mice failed to fully recapitulate the human phenotype, and patient-derived epithelial-only enteroids were difficult to propagate. This study aimed to determine the specific cellular compartment (epithelial vs. mesenchymal) responsible for the DIAR9 phenotype using a human intestinal organoid (HIO) model.

The researchers generated HIOs from patient-derived iPSCs carrying the WNT2B R69* mutation and transplanted them into immunocompromised mice to allow for tissue maturation. They performed histological analysis, transcriptomics, and proteomics to compare the mutant HIOs to controls. To pinpoint the causative compartment, they performed in vitro recombination experiments, separating and re-pairing epithelial and mesenchymal cells from mutant and control HIOs before transplantation.

Mutant WNT2B R69* HIOs successfully recapitulated key features of the human disease, including epithelial delamination (detachment from the basement membrane) and reduced stem cell activity (indicated by lower OLFM4 expression). Transcriptomic and proteomic analyses revealed significant downregulation of pathways related to apical digestion, nutrient transport, and cell-matrix adhesion. Crucially, the recombination experiments demonstrated that while both compartments contribute to stem cell function, the lack of mesenchymal WNT2B is sufficient to drive the severe intestinal architectural defects and epithelial delamination characteristic of the disease.

This study identifies mesenchymal WNT2B as a critical regulator of human intestinal development and homeostasis. By establishing that the mesenchymal compartment is the primary driver of the DIAR9 phenotype, the findings clarify the pathophysiology of this rare condition and suggest that therapeutic strategies should focus on restoring mesenchymal signaling or addressing the resulting epithelial-matrix adhesion defects. Furthermore, the successful use of the HIO transplantation model provides a robust platform for future personalized medicine approaches to congenital diarrheal disorders.