Helicobacter pylori triggers gastric mucosal remodeling toward a fetal-like transcriptional program via stromal IL-1β signaling.

In the gastrointestinal tract, Wnt and BMP signals control Lgr5⁺ stem cell activity during homeostasis, whereas injury elicits an Lgr5-independent, fetal-like regenerative program driven by YAP. Helicobacter pylori (H. pylori) infection activates YAP, but whether fetal-like reprogramming contributes to gastric pathology, and what drives it, has remained unclear. Here we show that H. pylori-induced gland hyperplasia is accompanied by YAP-dependent fetal-like transcriptional response and loss of epithelial BMP signaling. Epithelial BMP inhibition alone is sufficient to induce this program in vivo, through an epithelial-immune-stromal cascade: BMP-deficient epithelial cells secrete chemokines that recruit IL-1β-producing immune cells, and IL-1β drives enrichment of pro-regenerative fibroblasts producing prostaglandin E2. In gastric epithelial-stromal assembloids, IL-1β elicits stromal prostaglandin E2 production and subsequent epithelial YAP activation. Stromal deletion of the IL-1 receptor abrogates H. pylori-driven reprogramming and pathology. These data define a cascade that converts BMP loss into a fetal-like regenerative state and shapes H. pylori-associated gastric disease.