Fecal Microbiota Transplantation from Toddler Donors Ameliorated DSS-Induced Colitis in Mice by Reshaping Gut Microbiota

Background/Objectives: Gut microbiota dysbiosis is a key driver of inflammatory bowel disease (IBD), and fecal microbiota transplantation (FMT) has emerged as a potential therapeutic strategy. In this study, we investigated the protective effects of toddler-derived FMT against colitis and elucidated the underlying mechanisms. Methods: Firstly, fecal microbiota from healthy toddlers was transplanted into antibiotic-pretreated mice, establishing stable colonization between days 14 and 21 post-transplantation. Results: In a dextran sulfate sodium-induced colitis model, FMT significantly ameliorated colitis symptoms, including reduced disease activity index and restored colon length. Toddler-derived FMT improved the intestinal barrier by preserving goblet cell density and enhancing MUC2 expression. Meanwhile, colonic inflammation was alleviated by FMT, which suppressed pro-inflammatory cytokines, reduced CD4+ T cell counts, and associated with downregulation of JAK/STAT-related transcripts. 16S rRNA sequencing revealed that FMT remodeled the gut microbiota by enriching beneficial genera, including Bacteroides, Parabacteroides, Blautia, and Akkermansia, which correlated positively with colon length and negatively with inflammatory markers. Conclusions: These findings provided a theoretical foundation that toddler-derived microbiota represents a potential donor source for FMT in IBD.