Uterine physiology and conceptus development in pigs

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The uterine physiology of litter-bearing species supports and accommodates the simultaneous development of multiple conceptuses throughout gestation. In litter-bearing mammals, a minimum number of developing embryos need to be present early in gestation to allow for recognition of pregnancy, maintenance of the corpus lutea and production of progesterone. Developing embryos migrate with the uterine lumen prior to implantation and in litter-bearing species this migration creates adequate spacing within the uterine lumen to permit development of the multiple conceptuses. Development of a litter in utero can be influenced by several factors including ovulation, fertilization and implantation rates, conceptus survival and development, the total number and quality of the conceptuses, as well as uterine capacity and placental efficiency. Uterine capacity refers to the number of the conceptuses that a uterus can carry through gestation to parturition. Limited uterine capacity is considered to be responsible for reduced piglet birth weight as a consequence of compromised placental development and higher competition among embryos. However the biological mechanisms that underlie uterine capacity in the pig and its impacts on the developing conceptus has not been fully elucidated. The proposed research will build on our recent research to understand the maternal-embryonic interface and strives to understand the biological factors related to uterine capacity that affect conceptus development in utero and ultimately the birth weight of the progeny. The objectives of the research proposed here are to: 1) identify biological processes, candidate genes and gene expression networks involved in piglet birth weight by comparing gene expression profiles of reproductive tissues and fetuses of different weight phenotypes; 2) investigate the role of epigenetic mechanisms in the birth weight phenotypes by comparing the methylation profiles of reproductive tissues and fetuses of different weight phenotypes. These assessments will provide fundamental knowledge of the critical steps involved in the development of a competent conceptus, as well as an insight into how the uterine environment affects regulatory processes. The research to be conducted will result in the identification of a multitude of candidate genes and gene products which are involved in the maternal-conceptus interactions of the pig and that would have implications for basic science, maternal management and biotechnology. This knowledge will be beneficial to Canada as it will be used to improve the reproductive efficiency of economically important species, such as swine, but will address how maternal embryo communication can influence human health