Chemogenetic placental activation and proteomic extracellular vesicle signatures predict functional roles across pregnancy and postpartum

Mechanisms underlying homeostatic regulation of maternal health during pregnancy and the postpartum period are critical yet remain understudied. Extracellular vesicles (EVs) are vital sources of cell-to-cell communication that maintain homeostasis and are at their highest circulating concentration during pregnancy. Recent studies have implicated EVs and their cargo as facilitators in important physiologic functions during pregnancy, including glucose and immune regulation, but precise mechanisms are not known. In this study we aimed to compare changes in EVs and their protein cargo using unbiased proteomic analyses across pregnancy and postpartum periods to assert unique EV functions. As expected, we found significantly higher EV concentrations during pregnancy relative to nonpregnant and postpartum groups. We identified unique EV protein profiles across groups suggesting EVs were highly responsive to their current environment and performing unique functions. Surprisingly, while postpartum mice had similar EV concentrations as nonpregnant, their EVs had the least overlap in protein composition between groups and the greatest number of proteins clustered in a biological function - a significant reduction around cell adhesion processes postpartum. Lastly, to examine a homeostatic role for maternal circulating EVs, we utilized a novel chemogenetic approach to control dynamic EV secretion and measured changes in maternal glucose regulation. We found that an acute increase in circulating EVs reduced maternal glucose sensitivity, keeping glucose levels elevated longer following a glucose challenge. In summary, these results demonstrate the unique EV protein cargo changes that occur in pregnancy and postpartum and their potential importance in maintenance of maternal health.