Effect of the periovulatory endocrine milieu on polyamines synthesis pathway in endometrium during the first week of the estrous cycle in cattle

Abstract

Reproductive efficiency represents a determining factor on the overall performance and profitability of livestock. Despite the significant improvement achieved by the Brazilian cattle industry following the use of hormonal protocols that improved the rate of inseminated animals, pregnancy rates remain low at first AI, indicating that a significant proportion of inseminated females failed to become pregnant. It has been established that a major factor affecting conception rates is early embryonic mortality, which encompasses a variety of aspects that may potentially interfere with the pre-implantation uterine environment. The premise of this proposal is that post-ovulatory variations in P4 concentrations regulate endometrial gene expression and, consequently, the qualitative and quantitative composition of the uterine secretions, thus influencing the receptivity of the uterus toward the early development of the conceptus. Among the numerous molecular pathways that are associated with uterine environment quality we propose the study of organic cations that regulate cellular processes such as growth, development and differentiation called polyamines as well the cellular proliferation and the oxidative stress. Furthermore, we propose that these pathways are under regulation of the peri-ovulatory endocrine milieu. The main hypothesis of this proposal is that the peri-ovulatory endocrine environment regulates the polyamine synthesis pathway, the endometrial cellular proliferation and the uterine redox environment in the endometrium during the first week of the estrous cycle in cattle. The aim of this proposal is to analyze the relative abundance of transcripts, the expression of key proteins in these processes as well as their cellular and tissue distribution in endometrial tissue, and compare these variables between two experimental groups with distinct post-ovulatory P4 concentrations. Experimental groups were obtained by means of hormonal manipulation of the pre-ovulatory follicle growth, which aimed to induce ovulation of larger follicles that resulted in larger corpora lutea and greater post-ovulatory P4 production (Large Follicle group; LF) or the opposite (Small Follicle; SF). It is expected that molecules that compose the polyamine synthesis pathway will be differentially regulated between groups LF and SF. The potential regulation of these pathways by different peri-ovulatory endocrine environments will be critical for the definition of molecular signatures associated with higher or lower probability of gestational success. More specifically, it is expected that molecules identified as differentially regulated by the proposed experimental model will be investigated as potential prognostic or diagnostic markers of the gestational success. (AU)