Mobiluncus mulieris Alters the Transcriptomic Profile of Cervicovaginal Epithelial Cells, Shedding Light on Molecular Drivers of Adverse Reproductive Outcomes

The vaginal microbiota plays a crucial role in reproductive health, with alterations in its composition linked to various adverse reproductive outcomes. These adverse outcomes are associated with vaginal microbiota characterized by the depletion of Lactobacillus spp. and the overgrowth of anaerobic bacteria, commonly referred to as community state type IV (CST IV). CST IV has been repeatedly associated with bacterial vaginosis and is a risk factor for sexually transmitted diseases and other reproductive disorders, such as preterm birth (PTB). While Gardnerella spp. are frequently implicated in the adverse outcomes associated with CST IV, another key member, Mobiluncus mulieris , is also associated with several adverse reproductive outcomes. However, the molecular mechanisms underlying its contribution remain poorly understood. Using an unbiased discovery approach, this study investigated the complex host-microbe interactions driven by M. mulieris across the distinct epithelial barriers of the lower reproductive tract. RNA sequencing revealed that live M. mulieris , its bacteria-free supernatant, and its extracellular vesicles (bEVs) induce unique transcriptional changes of the different epithelial cells lining the lower reproductive tract. Notably, all three components triggered diverse immune responses and inflammatory pathways, with bEVs exerting the most profound effects by activating inflammation through both toll-like receptor (TLR) 2 and TLR5. Additionally, M. mulieris altered the expression of pathways involved in extracellular matrix (ECM) organization, including increased expression of matrix metalloproteinase 9 (MMP9), a key mediator of ECM degradation linked to reproductive disorders such as PTB. These findings were further supported by clinical data showing elevated MMP9 levels in pregnant women with vaginal microbiota containing M. mulieris . These results demonstrate the broad transcriptional impact of M. mulieris across the lower reproductive tract epithelia and revealed how specific vaginal anaerobes drive complex host-microbe interactions that may contribute to adverse reproductive outcomes. This study also identifies potential therapeutic targets for mitigating M. mulieris -driven inflammation and ECM degradation in reproductive health.