Fecal microbiota transplantation ameliorates experimental colitis via gut microbiota and T-cell modulation

Abstract

Background: Emerging evidence has demonstrated that fecal microbiota transplantation (FMT) has a promising therapeutic effect on mice with experimental colitis and patients with ulcerative colitis (UC), although the mechanism of FMT is unclear.

Aim: To evaluate the protective effect of FMT on UC and clarify its potential dependence on the gut microbiota, through association analysis of gut microbiota with colon transcriptome in mice.

Methods: Dextran sodium sulfate (DSS)-induced experimental colitis was established and fecal microbiota was transplanted by gavage. Severity of colon inflammation was measured by body weight, disease activity index, colon length and histological score. Gut microbiota alteration was analyzed through 16S ribosomal ribonucleic acid sequencing. The differentially expressed genes (DEGs) in the colon were obtained by transcriptome sequencing. The activation status of colonic T lymphocytes in the lamina propria was evaluated by flow cytometry.

Results: Compared with the DSS group, the weight loss, colon length shortening and inflammation were significantly alleviated in the FMT group. The scores of disease activity index and colon histology decreased obviously after FMT. FMT restored the balance of gut microbiota, especially by upregulating the relative abundance of Lactobacillus and downregulating the relative abundance of Clostridium_sensu_stricto_1 and Turicibacter. In the transcriptomic analysis, 128 DEGs intersected after DSS treatment and FMT. Functional annotation analysis suggested that these DEGs were mainly involved in T-lymphocyte activation. In the DSS group, there was an increase in colonic T helper CD4⁺ and T cytotoxic CD8⁺ cells by flow cytometry. FMT selectively downregulated the ratio of colonic CD4⁺ and CD8⁺ T cells to maintain intestinal homeostasis. Furthermore, Clostri dium_sensu_stricto_1 was significantly related to inflammation-related genes including REG3G, CCL8 and IDO1.

Conclusion: FMT ameliorated DSS-induced colitis in mice via regulating the gut microbiota and T-cell modulation.

Keywords: Colitis; Fecal microbiota transplantation; Gut microbiota; T lymphocyte; Transcriptome sequencing.

Figure 1

Therapeutic fecal microbiota transplantation ameliorates dextran sodium sulphate-induced inflammation. A: Schematic representation of fecal microbiota transplantation treatment in the dextran sodium sulphate colitis model (n = 7 per group); B: Daily changes of bodyweight of each group during the disease process; C: Disease activity index scores of each group were evaluated after sacrifice; D: Macroscopic view of colon was observed, colon length from each group was measured; E: Serial sections of colon tissues were stained with hematoxylin and eosin, original magnification 200 ×, Histological scores of each group were determined. Values of ^aP < 0.05, ^bP < 0.01 and ^cP < 0.001 were considered as statistically significant. DSS: Dextran sodium sulphate; FMT: Fecal microbiota transplantation.

Figure 2

Fecal microbiota transplantation modulated the overall structure of gut microbiota. A and B: Heatmap of the relative abundance at the level of phylum and genus; C: The linear discriminant analysis effect size analysis at the level of genus in groups. CON: Control; DSS: Dextran sodium sulphate; FMT: Fecal microbiota transplantation.

Figure 3

Fecal microbiota transplantation significantly regulated the relative abundance of eight genera compared with dextran sodium sulphate group. Lactobacillus [^cP < 0.001, one-way analysis of variance (ANOVA)]; Lachnospiraceae_UCG-001 (^aP < 0.05, one-way ANOVA); Clostridium_sensu_stricto_1 (^cP = 0.001, one-way ANOVA); Turicibacter (^cP < 0.001, one-way ANOVA); Alistipes (^cP = 0.001, one-way ANOVA); Acetatifactor (^cP = 0.001, one-way ANOVA); Ruminococcus_1 (^bP < 0.01, one-way ANOVA); Ruminiclostridium_6 (^aP < 0.05, one-way ANOVA). CON: Control; DSS: Dextran sodium sulphate; FMT: Fecal microbiota transplantation.

Figure 4

Effect of fecal microbiota transplantation on colonic transcriptome in colitis mice. A: Venn diagram with genes regulated between dextran sodium sulphate (DSS) and fecal microbiota transplantation (FMT) or shared between the two sections; B: The top 30 gene ontology terms with the most significant enrichment between DSS group and control (CON) group (left), FMT group and DSS group (right). After DSS treatment (left), the differentially expressed genes in mice colon were mainly associated with immune system process, while after FMT (right), the differentially expressed genes were mainly related to metabolic process and immune response. GO: Gene ontology.

Figure 5

Therapeutic fecal microbiota transplantation modulates T cell phenotypes. A: Differentially expressed genes between control, dextran sodium sulphate (DSS) and fecal microbiota transplantation (FMT) group analyzed in Metascape; B: Colonic CD4⁺ and CD8⁺ T cells in DSS and FMT group; n = 4 mice per group; C: Bar charts of the percentage of T cells (^bP < 0.01). CON: Control.

Figure 6

Network analysis of fecal microbiota transplantation in colitis mice. A: Network visualizing significant gene-microbe correlations (r > 0.8, P < 0.05). B: Relative quantification of transcript level of indoleamine 2,3-dioxygenase 1 (IDO1), antimicrobial C-type lectin regenerating islet-derived 3 gamma (REG3G) and monocyte chemoattractant protein 2 (CCL8) in groups (all the P < 0.001, one-way analysis of variance). CON: Control; DSS: Dextran sodium sulphate; FMT: Fecal microbiota transplantation.

Figure 7

Summary scheme of the mechanisms underlying the therapeutic effect of fecal microbiota transplantation on experimental colitis. CCL8: Monocyte chemoattractant protein 2; CON: Control; DSS: Dextran sodium sulphate; FMT: Fecal microbiota transplantation; IDO1: Indoleamine 2,3-dioxygenase 1; REG3G: Antimicrobial C-type lectin regenerating islet-derived 3 gamma.