Site-Specific Cytotoxicity and Epithelial Host Defense Mechanisms to Sneathia amnii Infection in the Female Reproductive Tract
Paweł Łaniewski1, Adriana Tonachio1, Melissa Herbst-Kralovetz1,2,3 1Departments of Basic Medical Sciences and 2Obstetrics and Gynecology, College of Medicine-Phoenix, University of Arizona, Phoenix, AZ, USA; 3UA Cancer Center, University of Arizona, Tucson/Phoenix, AZ, USA
Sneathia species are emerging bacterial pathogens found in the lower and upper female reproductive tract (FRT). In recent clinical studies, we and others identified Sneathia spp. to be associated with serious gynecologic and obstetric sequelae, including cervical dysplasia/cancer, pelvic inflammatory disease and preterm birth. However, there is a fundamental gap that exists in understanding the functional impact of these bacteria throughout the FRT microenvironment that may contribute to disease and poor health outcomes. To determine the epithelial host response to Sneathia infection, we utilized two human three-dimensional (3-D) FRT epithelial cell models and a vaginal isolate Sneathia amnii strain Sn35. We used a reductionist approach and infected 3-D aggregates with S.amnii with a range of multiplicities of infection under anaerobic conditions. Morphological changes and host-bacteria interactions were visualized using scanning electron microscopy. Level of cytotoxicity was measured by lactate dehydrogenase assay. Acidic mucins were selectively stained by Alcian blue. Changes in gene expression were determined by real time quantitative PCR and gene expression arrays. S. amnii infection caused site-specific cytotoxicity compared to other bacterial vaginosis-associated bacteria. The 3-D endometrial aggregates infected with S. amnii exhibited a high level of cytotoxicity, which was not observed in the endocervical aggregates. Similarly, membrane blebbing, an indicator of apoptosis, was observed in 3-D endometrial cells following S. amnii infection. Bacteria frequently interacted simultaneously with multiple epithelial cells and localized in folds and crevices of 3-D aggregates. S. amnii also induced acidic mucin production in both endocervical and endometrial epithelial cells. Expression of proinflammatory cytokine genes were induced following S. amnii infection. Additionally, we showed that S. amnii infection altered expression of genes involved in regulating apoptosis and angiogenesis. These data suggest that S. amnii is a potential microbial driver of pathophysiological changes in the FRT that may contribute to obstetric and gynecological sequelae.