Bacterial Membrane Vesicles mediate intestinal Homeostasis - Exploring the Impact of Akkermansia muciniphila-derived Membrane Vesicles on the Mucus Barrier

Abstract

Introduction: Maintaining symbiosis between the gut microbiome and its host requires a delicate balance between pathogen clearance and tolerance towards commensal bacteria. Akkermansia muciniphila is a key beneficial commensal that enhances epithelial barrier integrity and mucus production while inducing immunomodulation. As the name suggests, A. muciniphila is specialized in the mucosal habitat of the gut. Reductions in its abundance are associated with various diseases and a dysfunctional mucus barrier. Bacterial membrane vesicles (BMV) enable communication between host and microbiota by passing the mucus barrier. A. muciniphila mediates many beneficial effects by its outer membrane vesicles (OMV). They reduce intestinal permeability, modulate the immune system and ultimately support colonization with commensals. BMVs seem to play an essential role in maintaining intestinal homeostasis, but it is unknown whether A. muciniphila's OMVs also mediate its effects on the mucus barrier. Exploring this could provide valuable insights for the use of BMVs as a novel therapy option for inflammatory bowel diseases (IBD). These diseases are characterized by reduced A. muciniphila abundance and an impaired mucus barrier. Methods: To investigate the effects of A. muciniphila OMVs on the mucus system, we focused on goblet cell differentiation and MUC2 expression in intestinal cell lines. MUC2 expression not only measures mucus production but also suits as a goblet cell marker. Flow cytometry was used to determine the ratio of MUC2-positive LS174T cells and quantify their intracellular MUC2 levels. To gain deeper mechanistic insights, RT-qPCR was employed to assess the mRNA expression of goblet cell differentiation factors and mucins in HT-29-MTX cells. Results: In flow cytometry, we observed that LS174T cells expressed higher levels of MUC2 compared to other intestinal cell lines like HT-29 and HT-29-MTX. Treatment with the γ-secretase inhibitor DAPT resulted in an upregulation of MUC2 expression only in LS174T cells but not HT-29-MTX cells. However, A. muciniphila-OMV treatment did not significantly affect the number of MUC2-positive cells. RT-qPCR further showed that the expression of MUC2, MUC1, MUC5AC, KLF4, and AGR2 mRNA remained unaffected following OMV treatment. Discussion: This study has simplified the highly complex in vivo situation to an experimental model, which analyses only a fraction of the mucus system. As a result, broader effects of A. muciniphila OMVs cannot be ruled out by this approach. Experimental shortcomings are possible since the experimental use of BMVs is still being established. Nonetheless, BMVs provide a novel approach to restore intestinal homeostasis and are discussed as a therapeutic strategy for IBD. Finally, a conceptual model is proposed to illustrate the potential role of BMVs in IBD pathophysiology, emphasizing the disruption in the bidirectional communication between host and microbiome.

Datum der Bewilligung	2025
Originalsprache	Englisch
Gradverleihende Hochschule	Medizinische Universität Graz
Betreuer/-in	Gregor Gorkiewicz (Betreuer*in)