Human oviductal gonadotropin-releasing hormone: Possible implications in fertilization, early embryonic development, and implantation

The oviduct is host to gametes and early embryos at a critical paint in the ir lives. It is clear that the interactions of gametes/early embryo with th e maternal oviduct in an autocrine and paracrine manner provide a microenvi ronment that enhances fertilization, early embryonic development, and impla ntation. Moreover, there is considerable evidence that an extrahypothalamic GnRH may play a substantial role as a molecular autocrine/paracrine regula tor in these events. Gametes and preimplantation embryos express GnRH and G nRH receptor at both messenger ribonucleic acid (mRNA) and protein levels. However, whether GnRH is produced by the human oviduct has not yet been dem onstrated. We used RT-PCR and immuno-histochemical techniques to investigate GnRH mRNA and protein expression in human fallopian tubes throughout the menstrual c ycle of premenopausal fertile patients. Our results, at both the mRNA and p rotein levels, revealed cycle-dependent production of an oviductal GnRH wit h expression during the luteal phase. Moreover, GnRH immunostaining was loc alized in the tubal epithelium during the luteal phase. On the basis of these data, we suggest that during reproductive life, ovidu ctal GnRH may play a substantial paracrine/autocrine role in human fertiliz ation, early embryonic development, and implantation.