Placental and maternal microbiome adaptations in a preeclamptic-like mouse model.

Introduction: The maternal microbiome plays a crucial role in pregnancy with growing evidence supporting vertical microbial transmission from mother to fetus. The placenta, once considered sterile, may serve as a conduit for this transfer. We hypothesized that the placental microbial signatures would be distinctly different from oral, fecal, or vaginal microbiomes in pregnant mice. Methods: To test this hypothesis, the obese BPH/5 mouse (n=15), which spontaneously develops a preeclampsia (PE)-like phenotype, was compared to normotensive C57 (n=8) pregnant mice. 16S rRNA gene sequencing and bioinformatic analyses were conducted to assess microbial diversity and composition from samples collected at embryonic day 18.5 (feces, oral cavity, vagina, and placenta). Results: Alpha diversity analysis revealed that oral microbiomes of both BPH/5 and C57 were significantly less diverse compared to the placental microbial signatures (p = 0.019 and <0.001, respectively). Beta diversity analysis confirmed distinct microbial communities across body sites and between strains (p < 0.001), while no significant differences were detected in placental and vaginal microbiomes (p > 0.05). Microbial composition analysis showed site-specific variations at the phylum and genus levels with Firmicutes and Bacteroidetes being dominant across all sites. BPH/5 placentas were enriched in Discussion: These findings demonstrate that the placental microbial signatures are unique in a PE-like mouse model. Further studies are needed to elucidate the functional impact of these microbial differences on maternal and fetal PE outcomes.