Human Gastric Multi-Regional Assembloids Favour Functional Parietal Maturation and Allow Modelling of Antral Foveolar Hyperplasia

Patient-derived human organoids have the remarkable capacity to self-organise into more complex structures. However, to what extent gastric organoids can recapitulate human stomach physiological functions remain unexplored. Here, we report how region-specific gastric organoids can self-assemble into complex multi-regional assembloids showing functional response to drugs targeting the ATPase H+/K+ pump. The assembloids show preserved fundus, body, and antrum regional identity, and gastric-specific crosstalk pathways arise. The increased complexity and cross-communication between the different gastric regions, allow for the emergence of the elusive parietal cell type, responsible for the production of gastric acid, with functional response to drugs targeting the ATPase H+/K+ pump. Remarkably, we generated assembloids from PMM2-HIPKD-IBD paediatric patients (Phosphomannomutase 2 - Hyperinsulinemic hypoglycaemia and autosomal recessive polycystic kidney disease - Inflammatory bowel disease), a genetic condition found to be associated with unusual antral foveolar hyperplasia and hyperplastic polyposis. The cellular mechanisms behind such phenomena are poorly understood, and an exhaustive experimental model is needed. The {Delta}PMM2 multi-regional assembloid we have generated efficiently recapitulates hyperplastic-like antral regions, with decreased mucin secretion and glycosylated ATP4b, which results in impaired gastric acid secretion. Multi-regional gastric assembloids, generated using adult-stem cell-derived organoids, successfully recapitulate the structural and functional characteristics of the human stomach, offering a promising tool for studying gastric epithelial interactions and disease mechanisms previously challenging to investigate in primary models.