Background: The limitations of animal models of Neisseria gonorrhoeae (Gc) reproductive tract infection and human experimental urethral infection prevent a full understanding of the pathogenesis and host response when Gc interacts with its obligate human host. In particular, the mechanisms that allow Gc to thrive despite a robust immune response remain poorly understood.
Methods: We developed a biomimetic human endocervical microfluidic chip to model the lower female reproductive tract in the context of Gc infection. This chip consists of a fluidic cassette and a removable insert with two channels cut in medical-grade silicone, separated by a porous membrane. Primary human endocervical epithelial cells were seeded on top of a collagen gel matrix embedded with SHT290 endometrial stromal cells within the insert channel on top of the membrane. Human umbilical vein endothelial cells (HUVECs) were seeded onto the opposite side of the membrane, facing the second channel. This multilayered culture was matured in hypoxic conditions for one week with pumped medium to provide the shear stress needed for proper endothelial development. The epithelial surface was infected with an OpaD-locked Gc FA1090, followed by adding peripheral human blood neutrophils to the endothelial surface. Cultures were analyzed by microscopy, and cell supernatants were evaluated for cytokines, chemokines, and growth factors using a Luminex assay.
Results: A mature system comprised of polarized endocervical epithelium, collagen-embedded fibroblasts, and mature endothelium was established. Gc adhered to and grew on the epithelial cell surface over time. Neutrophils added to the endothelial cell surface transmigrated through the endothelial layer, membrane, collagen stroma, and epithelial layers in response to Gc epithelial infection. Neutrophils at the apical side of the epithelium interacted with the Gc encountered. Infection and neutrophil addition triggered release of innate immune mediators.
Conclusions: Microphysiological systems consisting of epithelia, stromal cells within a collagen matrix, neutrophils, and Gc recapitulate in vivo aspects of interactions of Gc with the female genital tract. We are currently evaluating how infection and the presence of each cell type contributes to the overall innate immune response. This information can help inform how new therapeutic modalities modulate infection and the consequent host response.