Stemness-associated MEF-derived extruded nanovesicles cooperate with Lactobacillus rhamnosus to alleviate DSS-induced colitis through mucosal microenvironment remodeling.

Lactobacillus rhamnosus (L. rhamnosus) can modulate intestinal microbiota, decrease harmful bacterial metabolites, and thereby improve the intestinal microenvironment of patients with ulcerative colitis (UC). However, rapid inactivation and low colonization efficiency caused by intestinal peristalsis and impaired mucosa severely restrict its therapeutic outcomes. Extracellular vesicles (EVs) exhibit excellent mucus-penetrating ability that enables them to reach deep intestinal crypts. Subsequently, EVs directly deliver repair signals to intestinal epithelial cells and immune cells, effectively promoting intestinal mucosal repair. In this study, we prepared stemness-associated mouse embryonic fibroblast-derived extruded nanovesicles (sMEF-eNVs) via small-molecule intervention and three-dimensional (3D) culture. The prepared sMEF-eNVs displayed nanoscale morphology, EV-associated phenotype expression, and physicochemical features consistent with those of EVs. In a DSS-induced mouse model of UC, sMEF-eNVs improved epithelial barrier integrity, increased tight-junction and mucus-associated barrier signals, and attenuated mucosal inflammatory responses. Combined administration of sMEF-eNVs and L. rhamnosus further alleviated disease activity, improved histological injury, modulated Th17/Treg-associated immune imbalance, and was accompanied by shifts in gut microbial composition and fecal metabolic profiles. These findings support a vesicle-probiotic combination strategy for intestinal inflammation.