L’oviducte de mammifère : un organe revisité

Maternal contributions to pregnancy success: from gamete quality to uterine environment

The establishment and maintenance of a pregnancy that goes to term is sine qua non for the long-term sustainability of dairy and beef cattle operations. The oocyte plays a critical role in providing the factors necessary for preimplantation embryonic development. Furthermore, the female, or maternal, environment where oocytes and embryos develop is crucial for the establishment and maintenance of a pregnancy to term. During folliculogenesis, the oocyte must sequentially acquire meiotic and developmental competence, which are the results of a series of molecular events preparing the highly specialized gamete to return to totipotency after fertilization. Given that folliculogenesis is a lengthy process in the cow, the occurrence of disease, metabolic imbalances, heat stress, or other adverse events can make it challenging to maintain oocyte quality. Following fertilization, the newly formed embryo must execute a tightly planned program that includes global DNA remodeling, activation of the embryonic genome, and cell fate decisions to form a blastocyst within a few days and cell divisions. The increasing use of assisted reproductive technologies creates an additional layer of complexity to ensure the highest oocyte and embryo quality given that in vitro systems do not faithfully recreate the physiological maternal environment. In this review, we discuss cellular and molecular factors and events known to be crucial for proper oocyte development and maturation, as well as adverse events that may negatively affect the oocyte; and the importance of the uterine environment, including signaling proteins in the maternal-embryonic interactions that ensure proper embryo development. We also discuss the impact of assisted reproductive technologies in oocyte and embryo quality and developmental potential, and considerations when looking into the prospects for developing systems that allow for in vitro gametogenesis as a tool for assisted reproduction in cattle.

GPR39 is region-specifically expressed in mouse oviduct correlating with the Zn2+ distribution

G-protein-coupled receptor 39 (GPR39) plays a role in cellular and physiological processes, including insulin secretion, cell death inhibition, wound healing, and obesity. Increasing evidence suggests that GPR39 is potently stimulated by zinc ions (Zn²⁺) and is therefore considered a putative Zn²⁺ receptor. Given the importance of Zn²⁺ in the reproductive system, we proposed that GPR39 might have a functional role in the reproductive system. However, the localization of GPR39 in the reproductive system remains unknown. Here, we used mice expressing a Gpr39 promoter-driven LacZ reporter system to detect Gpr39 expression in the reproductive system at different phases of the estrous cycle and found an interesting region-specific distribution of Gpr39 in the mouse oviduct epithelium, with strong expression at the ampulla and weak expression at the isthmus, which was consistent with the results using reverse transcription polymerase chain reaction and immunofluorescence. Moreover, using ZnSe^AMG staining, we found that Zn²⁺, the putative ligand of GPR39, also found a distribution similar to GPR39 expression, suggesting that their potential interaction mediates fertilization and embryo transportation.