Temporal and Spatial Characterization of Uterine and Oviductal Environment in the Pig

Abstract

Early embryonic development is a dynamic period that requires precise and timely interaction between the developing embryo and the maternal environment. A series of studies were carried out in order to identify the vital components of this environment and to understand their temporal and spatial changes during the period of cleavage stage development of the porcine embryo. This environment was characterized in animals following precise timing of ovulation using transcutaneous real time ovarian ultrasonography. Analysis of the glycosaminoglycan hyaluronic acid (HA) in this environment suggests a role for HA in fertilization and blastocyst development. In addition, analysis of the associated HA synthase (HAS) genes suggests a common regulatory mechanism at play in the oviduct and uterus for HAS 1 and 2, but not HAS3. Evaluation of the histotrophic proteome identified 269 unique proteins, ten of which were shown to significantly decrease and six significantly increased in abundance between the germinal vesicle and blastocyst stages. Fourteen proteins were identified by mass spectrometry revealing proteins such as CLU and CA2 in the histotroph at the germinal vesicle stage and members of the GST family at the blastocyst stage. These proteins likely play a role in maintaining a suitable environment for sperm and embryos respectively. Analysis of the associated transcripts suggests the majority of these changes are the results of either post-transcriptional regulation or changes in importation from another source. Additionally, microarray analysis of the temporal and spatial changes in the uterine transcriptome showed a decreasing spatial variation at the blastocyst stage. Gene ontology enrichment revealed an up-regulation of genes associated with signal transduction combined with a down-regulation in response to stimulus suggesting maternal-embryonic communication plays an important role in regulating the uterine environment. Finally, a novel bioinformatic program was developed to allow for the visualization of potential protein-protein interactions in paired sets of transcriptomic data; applied to transcriptomic data from the embryo and uterus this program identified multiple potential signaling pathways. In conclusion, these studies demonstrate the complexity of the uterine and oviductal environments and suggest the early embryo plays a role in modulating it.