Akkermansia muciniphila identified as key strain to alleviate gut barrier injury through Wnt signaling pathway

As the largest mucosal surface, the gut has built a physical, chemical, microbial and immune barrier to protect the body against pathogen invasion. The disturbance of gut microbiota aggravates pathogenic bacteria invasion and gut barrier injury. Fecal microbiota transplantation (FMT) is a promising treatment for microbiome-related disorders, where probiotic strain engraftment is a significant factor influencing FMT outcomes. The aim of this research was to explore the effect of FMT on antibiotic-induced microbiome-disordered (AIMD) model infected with enterotoxigenic Escherichia coli (ETEC). We used piglet, mouse and intestinal organoid models to explore the protective effects and mechanisms of FMT on ETEC infection. The results showed that FMT regulated gut microbiota and enhanced the protection of AIMD piglets against ETEC K88 challenge, as demonstrated by reduced intestinal pathogen colonization and alleviated gut barrier injury. Akkermansia muciniphila (A. muciniphila) and Bacteroides fragilis (B. fragilis) were identified as two strains that may play key roles in FMT. We further investigated the alleviatory effects of these two strains on ETEC infection in AIMD mice model, which revealed that A. muciniphila and B. fragilis relieved ETEC-induced intestinal inflammation by maintaining the proportion of Treg/Th17 cells and epithelial damage by moderately activating the Wnt/β-catenin signaling pathway, while the effect of A. muciniphila was better than B. fragilis. We therefore identified whether A. muciniphila protected against ETEC infection using basal-out and apical-out intestinal organoid models. A. muciniphila did protect the intestinal stem cells and stimulate proliferation and differentiation of intestinal epithelium, and the protective effects of A. muciniphila was reversed by Wnt inhibitor. FMT alleviated ETEC-induced gut barrier injury and intestinal inflammation in AIMD model. A. muciniphila was identified as key strain in FMT to promote proliferation and differentiation of intestinal stem cells by mediating the Wnt/β-catenin signaling pathway.