The role of extracellular vesicles throughout normal pregnancy and in relation to oral bacteria

Recently, the relationship between the maternal oral environment and complicated pregnancies has been discussed in depth. The depletion of all bacterial flora, including oral bacteria, significantly decreased the size of the maternal placenta and suppressed fetal bone reabsorption. Furthermore, bacterial flora DNA of the host placenta has been reported to be remarkably similar to that of oral flora DNA. These findings indicate that maternal oral flora has a considerable effect on the formation of the placenta and fetus.Placenta is a sophisticated tissue, in which the fetus and mother exchange substance. Placental homeostasis affects the maternal and fetal health; therefore, any disorder in this context is directly linked to serious health issues for the mother and developmental inhibition of the fetus. Extracellular vesicles (EVs) possess and deliver various factors (i.e., nucleic acids, proteins, and lipids) to distant organs through intercellular crosstalk. EVs are released during natural physiological events as well as under stress conditions. EVs derived from reproductive tissues, such as the placenta, are deeply involved in all stages of pregnancy, including the maturation and survival of sperm and egg, various events during fertilization, implantation, spiral artery remodeling, and immunomodulation.To date, the precise role of EVs in oral diseases, including periodontal disease, is not well understood. Nonetheless, placental EVs are likely to attract attention, in the future, to objectively evaluate the effects of periodontal disease on maternal and fetal health. Therefore, the role of EVs throughout normal pregnancy will be discussed in this review.