Sperm Binding to Oviduct Epithelial Cells Enhances TGFB1 and IL10 Expressions in Epithelial Cells as Well as Neutrophils In Vitro: Prostaglandin E2 As a Main Regulator of Anti-Inflammatory Response in the Bovine Oviduct

Abstract

Sperm are allogenic to the female genital tract; however, oviducts provide optimal conditions for survival and capacitation of these non-self cells until fertilization. Recently, we showed that oviduct-conditioned media and prostaglandin E2 (PGE2) suppress sperm phagocytosis by polymorphonuclear neutrophils (PMNs) under physiological conditions. We hypothesized that sperm binding to bovine oviduct epithelial cells (BOECs) could change the local innate immunity via PGE2. As the first step to obtain basic information, sub-confluent BOEC monolayers were co-cultured with swim-up sperm for 2 h. BOECs with viable bound sperm were cultured for an additional 3, 6, 12, or 24 h. Then, we confirmed the impact of the sperm-BOEC binding on both BOECs and PMN gene expression. Immunohistochemistry revealed that BOECs strongly express TGFB1 and IL10 in the oviduct. Sperm binding to BOECs in culture induced the anti-inflammatory cytokines (TGFB1 and IL10) and PGE2 production by BOECs. Exogenous PGE2 in vitro suppressed pro-inflammatory cytokine expression (TNF and IL1B) in BOECs. Moreover, pre-exposure of PMNs to BOEC-conditioned media suppressed the TNF expression, but the BOEC media co-cultured with sperm stimulated PMNs to express TGFB1 and IL10, with increasing PGE2 secretion. Of note, exogenous PGE2 led PMNs in vitro to decrease their TNF expression and increase anti-inflammatory cytokines expression. Our findings strongly suggest that BOECs provide an anti-inflammatory environment under physiological conditions and the sperm-BOEC binding further strengthens this milieu thus suppresses PMNs in the bovine oviduct. PGE2 is likely to drive this stable anti-inflammatory environment in the oviduct.

A proinflammatory response of bovine endometrial epithelial cells to active sperm in vitro

“…More is known about how sperm interact with bovine oviductal epithelium. We recently demonstrated that sperm binding to monolayer cultures of bovine oviduct epithelial cells (BOECs) produces an anti‐inflammatory environment and suppresses sperm phagocytosis by PMNs in vitro (Marey et al, , Yousef et al, ). Using a similar in vitro model, we aimed to investigate the immunological response of bovine uterine epithelial cells (BUECs) to sperm.…”

Ovulatory follicular fluid induces sperm phagocytosis by neutrophils, but oviductal fluid around oestrus suppresses its inflammatory effect in the buffalo oviduct in vitro

“…To date, little has been known about the exact role of neutrophils in the oviduct. It is supposed that besides their primary function in innate immunity against different pathogens, they play an important role in maintaining normal oviductal physiology (Smith, Wira, Fanger, & Shen, ) and help regulate oviductal immunity by secretion of their cytokines (i.e., PGE 2 ) to be favourable for sperm (Yousef et al, ) and subsequent successful fertilisation. The final sperm selection by oviductal neutrophils before fertilization and removal of the excess sperm after fertilization by phagocytosis is also hypothesized (Eisenbach, ).…”

“…It was demonstrated that PGE 2 secreted from BOEC acts as one of the main regulators for suppression of sperm phagocytosis by neutrophils in the bovine oviduct (Marey et al, ). PGE 2 can lead neutrophils to decrease their TNF expression, increase anti‐inflammatory cytokine expression (Yousef et al, ), and inhibit sperm phagocytosis in vitro (Marey et al, ).…”

“…Therefore, it can be claimed that FF released during ovulation induces local inflammation in the oviduct (King et al, ), and preovulatory oviduct fluid can overcome the transient inflammatory action of FF and support sperm against phagocytosis. Moreover, sperm attachment to the oviduct epithelia strengthens the anti‐inflammatory environment of the oviduct (Yousef et al, ).…”

“…Neutrophils were isolated as previously described (Yousef et al, ) with minor modifications. Blood collections were conducted at the Faculty of Veterinary Medicine, Assiut University, Egypt.…”