An Ex Vivo System of Human Cervical Tissue to Study the Immunoregulatory Effect of Seminal Plasma on the Female Genital Mucosa

Background. Semen deposition on the female genital mucosa (FGM) induces a local inflammatory response. Although this phenomenon has long been reported, its underlying mechanisms and implications for susceptibility to infections remain largely unknown due to the lack of comprehensive experimental systems. To this purpose, we developed and validated an ex vivo model of coitus. Methods. Polarized explants of human ectocervical mucosa were exposed to seminal plasma (SP) diluted 1:1 or 1:3, or culture medium, for 2, 4 or 12 hours. In situ apoptosis was evaluated using a TUNEL assay. Protein and gene expression of pro-inflammatory/growth factors were measured in culture supernatant and tissue respectively. Attraction of peripheral blood leukocyte by supernatants was assessed with a transwell migration assay. Explants exposed to SP were infected with HIV-1_BaL and viral replication was measured as p24_gag antigen release in supernatant. Results. In comparison to explants incubated with culture medium, exposure to SP resulted in: equal fraction of apoptotic cells; increased expression of IL-1α, IL-6, TNF-α, CXCL1, CXCL8, CCL20, CSF2, IL-7, and cyclooxygenase 2; higher number of migrating leukocytes, mostly neutrophils and monocytes. Treatment of explants with the cyclooxygenase inhibitor indomethacin did not affect SP-induced changes in protein and gene expression. Finally, explants exposed to SP supported productive HIV-1 replication. Conclusions. Exposure of human cervical explants to SP recapitulates the main features of the response occurring in the FGM upon coitus. Our system will be implemented to further characterize this response and understand its genesis, and potential contribution to HIV-1 transmission to the FGM.