The effect of Akkermansia muciniphila and its outer membrane vesicles on the expression of microRNAs involved in the maturation of monocyte-derived human dendritic cells

Akkermansia muciniphila, an important member of the gastrointestinal microbiota, is involved in the functioning of the host immune system. We aimed to investigate the effect of A. muciniphila and its OMVs on the expression of microRNA-21 and microRNA-34a involved in the maturation of human dendritic cells. A. muciniphila was cultured on a mucin-containing medium and its OMVs were extracted by ultracentrifugation. Extraction of peripheral blood mononuclear cells (PBMCs) was performed using Ficoll’s density gradient centrifugation method. Monocytes were differentiated into dendritic cells in the presence of interleukin-4 cytokines and granulocyte-monocyte colony-stimulating factor. Then, A. muciniphila at MOI 50 and 100, OMVs at a dose of 50 µg/µl, dexamethasone (to induce tolerogenic dendritic cells), and the LPS (to induce mature dendritic cells) were incubated. Finally, the expression of microRNA-21 and microRNA-34a was measured by real-time PCR. The morphological characteristics of the extracted OMVs showed that their size was between 20-200 nm. In LPS treatment, there were longer cytoplasmic growths than OMVs of dexamethasone and A. muciniphila groups. MicroRNA-21 expression was decreased in the LPS group compared to dexamethasone, A. muciniphila, and OMV groups, although this decrease was not significant (P> 0.05). In addition, microRNA-34a expression was significantly increased in the LPS group, which was reversed by treatment with dexamethasone, A. muciniphila, and OMV (P <0.001). MicroRNA-21 and microRNA-34a can exhibit anti-inflammatory and pro-inflammatory functions. A. muciniphila and its OMVs appear to be a viable option for introduction as a new generation probiotic.