Role of TLR7/8-activating microRNAs in fetal inflammatory response syndrome - Preterm birth is commonly associated with chorioamnionitis; infection/inflammation of the fetal membranes (FM). Pathogens contributing to this do not typically cross the placenta. However, abnormal maternal and/or placental immune responses can cause inflammation in the fetus, contributing to Fetal Inflammatory Response Syndrome (FIRS). FIRS is a systemic activation of the fetal immune system associated with fetal injury and lifelong health issues. The mechanisms by which maternal/placental immune responses induce fetal inflammation, the method of communication between mother and fetus, and the breadth of fetal developmental consequences are not fully understood. FMs generate inflammatory responses to infections through activation of Toll-like receptors (TLRs). A novel family of microRNAs (miRs) can induce sterile inflammation through the ssRNA sensors, TLR7 and TLR8. We found an intermediate role for TLR7/8-activating miR-146a-3p in driving FM inflammation via TLR8, downstream of TLR4 activation by bacterial LPS. In preliminary studies, we found TLR7/8-activating miR-21a and miR-29a are elevated in exosomes released from bacterial LPS- and viral Poly(I:C)-stimulated human FMs, and in amniotic fluid exosomes of pregnant mice exposed to LPS. Preliminary data also show maternal exposure to LPS increases fetal brain, tail, and gut inflammatory IL-1b and KC (IL-8) in wildtype (WT) mice but not in TLR7- /-/TLR8-/- mice. Thus, our central hypothesis is that maternal infection induces FMs to release exosomes containing TLR7/8-activating miRNAs into the amniotic fluid which drive sterile fetal inflammation via TLR7/8 signaling. This leads to FIRS and subsequent developmental consequences. We will determine if: FM/amniotic fluid-derived exosomes containing TLR7/8-activating miRs mediate sterile fetal inflammation (Aim 1); Fetal inflammation, injury and altered development after a maternal infection is dependent on exosomes causing fetal TLR7/8 signaling (Aim 2); and Exosomes carrying TLR7/8-activating miRs traffic via the amniotic fluid to cause fetal inflammation and injury through initial contact with the fetal skin and gut (Aim 3). During the first two aims, the PI will gain valuable training and experience in various in vitro, ex vivo and in vivo models along with mouse fetal manipulations, exosome biology, and fetal immune and organ development (K99 Phase). Under the guidance of her primary mentor, Dr Vikki Abrahams, her expert mentorship and advisory teams, and exceptional training resources at Yale University, the PI is well positioned to establish herself as an independent investigator in Reproductive Immunology following her K99 training phase. After securing a faculty position and transitioning to the R00, the PI will use her newly acquired skills and expertise to study maternal/fetal exosome trafficking and TLR7/8-activating miR function and signaling in vivo at her new institution. The proposed studies are significant because they will establish a role for exosomes and TLR7/8 signaling in the initiation of sterile fetal inflammation and its subsequent impact on fetal/neonatal development, providing critical insight into the mechanisms underlying FIRS for future work in prevention, treatment, and advancement of maternal/fetal medicine.
