Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA, Massachusetts, United States
Abstract: The reproductive health of a woman is strongly associated with a vaginal microbiome mainly composed of Lactobacillus species, whereas dysbiosis leads to a decrease in this population and an increase in diversity of anaerobic species including pathogens, such as Garderenella vaginalis, as seen in bacterial vaginosis (BV). BV increases the risk of pre-term birth, miscarriages and the chances of acquiring sexually transmitted diseases. Various therapeutic strategies are being explored to modulate the composition of the vaginal microbiome; however, there is no human-relevant preclinical model that faithfully reproduces the vaginal epithelial microenvironment for validation of potential therapeutics. Here, we describe a high-content Organ Chip microfluidic culture model of the human vaginal mucosa that is lined by hormone-sensitive, primary vaginal epithelium interfaced with underlying stromal fibroblasts, which sustains a low physiological oxygen concentration in the epithelial lumen. The Vagina Chip supports establishment of healthy commensal vaginal microbiome consisting of Lactobacillus sp., as well as maintenance of epithelial cell viability, increased D-lactate, pH reduction, and down-regulation of proinflammatory cytokines, all of which are observed in healthy vagina. In contrast, culturing synthetic Gardnerella vaginalis-containing consortia in the Vagina Chip results in epithelial cell injury, a rise in pH, and upregulation of proinflammatory cytokines. We then used the engineered vaginal tissue to test the efficacy of Lactobacillus-rich live biotherapeutic products (LBPs) currently in development to improve the reproductive health of women. When we cultured microbes isolated from clinical vaginal swab samples obtained from both untreated and antibiotic-treated BV patients in the Vagina Chip, we detected higher pro-inflammatory responses in chips populated with untreated BV patient samples compared to samples from antibiotic-treated patients, hence correlating with increased inflammation observed in untreated BV patients. The Lactobacillus-rich LBPs alleviated this dysbiotic response on-chip by reducing pro-inflammatory responses and cell death. Interestingly, we did not observe a reduction in the number of G. vaginalis present in the chips. These data suggest that the Lactobacillus directly suppresses production of inflammatory cytokines, and that this does not require eradication of G. vaginalis from the vaginal epithelium. Additional studies will be required to explore whether further reduction in G. vaginalis numbers will produce an even greater therapeutic effect on the inflammation response. Altogether, our study indicates that the human Vagina Chip is a powerful preclinical tool that may be used to understand host-microbiome interactions in the reproductive tract and to test potential new therapeutic strategies for vaginal diseases.