Gut microbiota-derived extracellular vesicles in the brain and the fetal environment

Human gut microbiota is essential for human health. Changes in gut microbiota composition are associated with many different diseases. The mechanisms behind how gut microbiota communicates with the human body remain poorly understood. Extracellular vesicles (EVs) are lipid-coated nanoparticles secreted by all cells, including bacteria. EVs secreted by human gut microbiota have been suggested to be able to cross biological barriers; escape the gut, enter the circulation and thus reach distal organs, including the brain. This thesis investigated gut microbiota-derived EVs as a communication mechanism between the gut microbiota and the body, focusing on EV-mediated crosstalk between the gut microbiota and the brain, and maternal gut microbiota and fetus in healthy pregnancy. The results suggest that gut microbiota-derived EVs form a distinct entity from the gut microbiota with vast potential in explaining how gut microbiota orchestrates its communication with different body systems. In pregnancy, maternal gut microbiota communicates with the fetus via gut microbiota-derived EVs. In conclusion, gut microbiota-derived EVs are a new dimension to gut microbiota function and crosstalk with the body. In the future, gut microbiota-derived EVs should be investigated alongside gut microbiota composition when conducting clinical studies on human gut microbiota. In pregnancy, EVs derived from maternal gut microbiota are likely to be a mechanism how maternal gut microbiota prepares fetal gut and immune system towards gut colonization after birth.