O-019 Decreased Sperm Motility Associated With Bacterial Vaginosis Modeled in a Human Cervix Chip
Authors: Gutzeit O , Izadifar Z , Gulati A , Junaid A , Stejskalova A , Lee Marquez S , Shcherbina K , Goyal G , Ingber D E 
Published: June 2023

Abstract

Study question
What is the underlying cause of infertility associated with bacterial vaginosis (BV)?

Summary answer
We provide the first evidence to suggest that BV-associated infertility could be the result of sperm dysfunction induced by exposure to poor cervical microbiome.

What is known already
Infertility is a global health concern, impacting 186 million individuals worldwide. In 25% of infertile couples the underlying cause remains unexplained. The complex interactions between the host mucosal epithelium, microbiome, and other microenvironmental factors play a significant role in health and disease of the reproductive tract. BV affects 30% of reproductive-aged women and is linked to overgrowth of pathogenic Gardnerella vaginalis bacteria. BV has a strong association with infertility, but it is not clear whether the resulting changes in the vaginal microbiome play a causal role, and as such BV screening is not currently included in infertility evaluation or treatment

Study design, size, duration
Female reproductive tract protective factors such as cervical mucus helps sperm retain their ability to fertilize for days compared to hours in suspension. We previously leveraged human organ-on-a-chip microfluidic culture technology to develop a physiological in vitro model of human cervix (Cervix Chip) that is lined with primary cervical epithelium interfaced with stromal fibroblasts. The epithelium forms a functional tissue barrier and produces mucus with compositional, biophysical, and hormone-responsive properties similar to the living cervix.

Participants/materials, setting, methods
We used 2D culture of sperm and bacteria as a screening and validated the effect of the identified bacteria on physiological in vitro Cervix Chip. A BV consortium containing E2 and E4 Gardnerella vaginalis bacteria was co-cultured with the Cervix Chip for 48 hours before adding human sperm samples. The motility of fluorescently labeled sperm was non-invasively evaluated in live chips using time-lapse imaging and quantitatively analyzed to obtain the percentage of motile sperm.

Main results and the role of chance
We initially analyzed the effects of bacterial co-cultur L. crispatus (optimal) or G. vaginalis (suboptimal) bacteria on sperm motility using a conventional 2D culture system. We observed a significant drop in sperm motility within 2 hours when exposed to G. vaginalis compared to L. crispatus or the control condition (no bacteria). We have established sperm staining and live tracking on Cervix Chip. Motile sperm was tracked on Cervix Chip for more than 7 days compared to 12 hours in suspension. We then tested this effect on-chip and observed that co-culture of live sperm with dysbiotic Cervix Chip (infected with G. vaginalis) resulted in a significant reduction in the sperm motility within 24 hours after exposure compared to the sperm exposed to the chips without bacteria. The dysbiotic Cervix Chip also exhibited a disease phenotype with elevated levels of proinflammatory cytokines including IL-1α, IL-1β, IL-6, IL-8, and TNF-α in the effluents of the chip's epithelial channel as well as significantly reduced thickness of the cervical mucus layer that correlated with reduced sperm motility. This finding is consistent with the observation that successful fertility is often associated with the quality of cervical mucus, which can be compromised in the BV dysbiotic condition.

Limitations, reasons for caution
Primary cervical epithelium cells used in the study were sourced from a single donor. Frozen sperm samples prepared for intrauterine insemination were used in the study

Wider implications of the findings
Our study suggests that infertility related to BV may be caused by sperm dysfunction, and BV screening should be considered in patients with unexplained infertility. We propose a model that can be used to identify dysbiotic conditions in the female reproductive tract that are unfavorable to sperm motility.

Trial registration number
N/A