<i>Akkermansia muciniphila</i> identified as key strain to alleviate gut barrier injury through Wnt signaling pathway.

Abstract

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 beneficial 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) models infected with enterotoxigenic <i>Escherichia coli</i> (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. <i>Akkermansia muciniphila</i> (<i>A. muciniphila</i>) and <i>Bacteroides fragilis</i> (<i>B. fragilis</i>) 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 the AIMD mice model, which revealed that <i>A. muciniphila</i> and <i>B. fragilis</i> 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 <i>A. muciniphila</i> was better than <i>B. fragilis</i>. We, therefore, identified whether <i>A. muciniphila</i> protected against ETEC infection using basal-out and apical-out intestinal organoid models. <i>A. muciniphila</i> did protect the intestinal stem cells and stimulate the proliferation and differentiation of intestinal epithelium, and the protective effects of <i>A. muciniphila</i> were reversed by Wnt inhibitor. FMT alleviated ETEC-induced gut barrier injury and intestinal inflammation in the AIMD model. <i>A. muciniph</i>ila was identified as a key strain in FMT to promote the proliferation and differentiation of intestinal stem cells by mediating the Wnt/β-catenin signaling pathway.