Equine oviduct-specific glycoprotein is modulated by hormones and sperm cells

Oviduct glycoprotein 1 (OVGP1) is a key protein involved in oviductal functions. β-estradiol (E₂) and progesterone (P₄), oxytocin (OXT) and tumor necrosis factor-α (TNFα) modulate the equine oviduct function, through prostaglandin regulation. The objective was to evaluate OVGP1 expression within each equine oviduct segment (infundibulum, ampulla isthmus), throughout the estrous cycle. The in vitro effect of (i) E₂, P₄, OXT, TNFα; and (ii) spermatozoa, on oviduct OVGP1 transcription and secretion was studied. Gene transcription was assessed by real-time PCR; protein expression by western blot; and protein production by enzyme immunoassay. OVGP1 mRNA increased in the ampulla, in the early-luteal phase (P < 0.05). OVGP1 protein expression increased in the follicular phase, in all portions (P < 0.05). A temporal desynchronization between transcription and protein synthesis might maintain oviduct function. In ampulla explants, OXT and TNFα up-regulated OVGP1 transcripts in follicular phase; E₂ in early-luteal phase; and P₄ in mid-luteal phase (P < 0.05). OXT and TNFα effect on OVGP1 transcripts might be ascribed to prostaglandin modulation. Oviductal endogenous E₂ in follicular phase, could prime E₂ stimulation of OVGP1 transcripts in early-luteal phase. The stimulatory effect of P₄ on OVGP1 transcripts may modulate early embryogenesis. OVGP1 in vitro production was not dependent of E₂, P₄, OXT or TNFα treatments. Sperm cells, either in direct or indirect contact with oviduct explants, up-regulated OVGP1 production, in the isthmus (P < 0.05). These data suggest that OVGP1 modulates sperm and mare's oviduct cross-talk and may play an important role in improving assisted reproductive technologies.