Interactions between placental Hofbauer cells and L. monocytogenes change throughout gestation

Hofbauer cells (HBCs) are extraembryonic macrophages generated de novo within the human placenta. In this study, we explored how the properties of HBCs change throughout gestation. Our analysis revealed transcriptomic differences between first-trimester and term HBCs, with many of the altered genes linked to immune responses. As pregnancy progresses, HBCs exhibit a marked decrease in phagosome maturation and acidification. We show that the differences between first-trimester and term HBCs are important in the context of infection with Listeria monocytogenes, a pathogen that crosses the placenta and replicates within macrophages. Specifically, we observed reduced colony-forming units and diminished actin recruitment by L. monocytogenes in first-trimester HBCs compared with term HBCs. Our findings indicate that the ability of L. monocytogenes to escape from vacuoles is impaired within first-trimester HBCs. Thus, the changes in HBC biology across pregnancy are important in shaping their interactions with L. monocytogenes.