Fecal Microbiota Transplantation Reconstructs The Gut Microbiota Of Septic Mice And Protects The Intestinal Mucosal Barrier

Objective: This study aimed to confirm the existence of gut microbiota(GM)imbalance in the early stage of sepsis,observe the effect of fecal microbiota transplantation(FMT)on sepsis,and explore whether FMT can reconstruct the GM of septic mice and restore its protective function on intestinal mucosal barrier.Methods: Clean-grade C57BL/6 male mice(6-8 weeks old,bodyweight 20-25g),were included in the experiments after one week of adaptive feeding.The study included acute experiments and 7-day mortality observation experiments.The animals in the acute experiment were randomly divided into three groups by random number,namely,the sham group(Sham group)(n = 18,n = 6 per timepoint),the sepsis model group(CLP group)(n = 31,n = 10/11 per timepoint)and the fecal microbiota transplantation group(FMT group)(n = 31,n = 10/11 per timepoint).The mortality observation experiment was divided into the same groups,with n = 10 per group.The Sham group underwent laparotomy without cecal ligation and puncture,while both the CLP group and FMT group underwent cecal ligation and puncture to mimic sepsis models.Fresh feces from 10 mice were kept every day to make fecal liquid.The Sham group and the CLP group were given intragastric administration once a day with phosphate-buffered saline,and the FMT group mice were given fecal microbiota transplantation once a day.The operations were performed simultaneously at a fixed time every day.All of the experimental animals had access to the same food and water ad libitum and were kept in the same environment.The animals were euthanized at 12,24,and 48 h after modeling,and blood,colon,and stool from each mouse were collected at the same time.Results: The 7-day survival rate in the CLP group was 50%,which was significantly lower than that in the Sham and FMT groups.Colonic pathological scores,including the expression of caspase 3,pro-inflammatory cytokines,TLR4/My D88/NF-?B protein levels,and gene expression levels,were lower in the FMT group,while anti-inflammatory factors,mucus layer thickness,MUC2,occludin,and ZO-1 proteins were higher in the FMT group than the CLP group.Bacterial flora analysis showed gut flora was reconstructed after FMT,with a higher abundance and diversity in those of septic mice.The species composition of the differential pathways revealed that the Lachnospiraceae group contributed the most by the L-lysine pathway of fermentation to acetate and butanoate.Conclusion: GM imbalance exists early in sepsis.Fecal microbiota transplantation can improve morbidity and effectively reduce mortality in septic mice.After the fecal bacteria were transplanted,the abundance and diversity of the gut flora were restored,and the microbial characteristics of the donors changed.Fecal microbiota transplantation can effectively reduce epithelial cell apoptosis,improve the composition of the mucus layer,upregulate the expression of tight junction proteins,and reduce intestinal permeability and the inflammatory response,thus protecting the intestinal barrier function.After FMT,Lachnospiraceae contributes the most to intestinal protection through enhancement of the L-lysine fermentation pathway,resulting in the production of acetate and butanoate,and may be the key bacteria for short-chain fatty acid metabolism and FMT success.