Crohn’s disease-associated AIEC inhibiting intestinal epithelial cell-derived exosomal let-7b expression regulates macrophage polarization to exacerbate intestinal fibrosis

ABSTRACT

The interaction between adherent-invasive Escherichia coli (AIEC) and intestinal macrophages is implicated in the pathogenesis of Crohn’s disease (CD). However, its role in intestinal fibrogenesis and the underlying molecular mechanisms are poorly understood. In addition, miRNAs such as let-7b may participate in AIEC-macrophage interactions. In this study, we identified that the colonization of AIEC in the ileum was associated with enhanced intestinal fibrosis and reduced let-7b expression by enrolling a prospective cohort of CD patients undergoing ileocolectomy. Besides, AIEC-infected IL-10^−/− mice presented more severe intestinal fibrosis and could be improved by exogenous let-7b. Mechanistically, intestinal macrophages were found to be the main target of let-7b. Transferring let-7b-overexpressing macrophages to AIEC-infected IL-10^−/− mice significantly alleviated intestinal fibrosis. In vitro, AIEC suppressed exosomal let-7b derived from intestinal epithelial cells (IECs), instead of the direct inhibition of let-7b in macrophages, to promote macrophages to a fibrotic phenotype. Finally, TGFβR1 was identified as one target of let-7b that regulates macrophage polarization. Overall, the results of our work indicate that AIEC is associated with enhanced intestinal fibrosis in CD. AIEC could inhibit exosomal let-7b from IECs to promote intestinal macrophages to a fibrotic phenotype and then contributed to fibrogenesis. Thus, anti-AIEC or let-7b therapy may serve as novel therapeutic approaches to ameliorate intestinal fibrosis.

Plain Language Summary

What is the context?

• Adherent-invasive Escherichia coli (AIEC) plays an important role in the pathogenesis of Crohn’s disease (CD) and has a strong association with intestinal fibrosis in animal models. However, how these bacteria contribute to intestinal fibrosis in CD patients is still unclear.

• The plasticity of macrophages is crucial in immune tolerance and tissue repair in the gastrointestinal tract, and the abnormal interaction between macrophages and gut bacteria triggers the fibrogenesis in the intestine.

• The association between the miRNA let-7b and fibrosis process has been widely reported in many tissues, except the intestine.

What is new?

• AIEC colonization in the terminal ileum is associated with severe intestinal fibrosis in CD patients and the let-7b plays an anti-fibrotic role in intestinal fibrosis.

• Intestinal macrophages are the key modulator of AIEC-induced fibrosis and can be promoted to an antifibrotic phenotype through let-7b-targeted TGFβR1 inhibition.

• AIEC suppresses intestinal epithelial cell-derived exosomal let-7b to promote intestinal macrophages to a fibrotic phenotype, rather than a direct effect on macrophage regulation.

What is the impact?

• Anti-AIEC and let-7b therapy may serve as potential therapeutic strategies to reduce intestinal fibrosis in CD in the future.

KEYWORDS:

• Crohn’s disease
• adherent-invasiveEscherichia coli
• macrophage
• miRNA
• intestinal fibrosis

Acknowledgments

We sincerely appreciate the Prof. Zhaoyu Lin of Model Animal Research Center, Medical School of Nanjing University participating in this study for his help of experiments implementation and discussion. We thank Prof. Wu Kaichun (Air Force Medical University, Xi’an, China) for providing E coli LF82 strain and the University of Auvergne (Clermont-Ferrand, France) for giving the permission to use E coli LF82 strain.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

Weiming Zhu, Zhen Guo and Yihan Xu conceived and designed the study. Yihan Xu, Wenwei Qian, Liangyu Huang and Weiwei Wen performed experiments, analyzed the data and wrote the manuscript. Yi Li, Zhenxing Zhu, Feilong Guo and Jianfeng Gong reviewed and edited the manuscript. Zhun Li, Yan Zhou, Nan Lu and Zeqian Yu recruited patients, collected the specimens and isolated bacteria. All the authors approved the final version of the manuscript.

Data availability statement

The datasets and methodology for screening miRNA targets are uploaded to the Figshare universal data repository (https://doi.org/10.6084/m9.figshare.22299679.v2). Additional information are available from the corresponding author upon request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/19490976.2023.2193115.

Additional information

Funding

This work was supported by the grants from the Project of Jiangsu Provincial Health Commission (M2021013), Scientific Research and the Science Foundation of Jinling Hospital (YYMS2021035), National Natural Science Foundation of China (82270543, 82170573, 81500429, and 81770556).