Metabolic compounds within the porcine uterine environment are unique to the type of conceptus present during the early stages of blastocyst elongation

Authors: WALSH, SOPHIE - University Of Nebraska; Miles, Jeremy; YAO, LINXING - Colorado State University; BROECKLING, COREY - Colorado State University; Rempel, Lea; Wright, Elane; PANNIER, ANGELA - University Of Nebraska

Submitted to: Journal of Molecular Reproduction and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2019
Publication Date: 1/1/2020
Citation: Walsh, S.C., Miles, J.R., Yao, L., Broeckling, C.D., Rempel, L.A., Wright-Johnson, E.C., Pannier, A.K. 2020. Metabolic compounds within the porcine uterine environment are unique to the type of conceptus present during the early stages of blastocyst elongation. Journal of Molecular Reproduction and Development. 87:174-190. https://doi.org/10.1002/mrd.23306.
DOI: https://doi.org/10.1002/mrd.23306

Interpretive Summary: In the pig, deficiencies in embryo elongation contributed to approximately 20% of the embryonic loss, and have a direct influence on within-litter birth weight variation, which influences preweaning piglet survival. Alterations in the signaling of critical molecular factors within the uterine environment result in deficiencies in embryo elongation, leading directly to embryonic loss as well as delayed elongation. The objective of this study was to identify critical metabolomic factors within the maternal uterine environment necessary to initiate and progress embryos thru early stages of elongation using non-targeted metabolomics (GS-MS & UPLC-MS) of uterine milieu containing uniform or diverse populations of embryos as they transition between the initiation and early stages of elongation. This study identified 97 metabolites within the uterine milieu that temporally changed as pig embryos transition from pre-elongation stage spherical morphology thru transitional ovoid and tubular morphologies. Some of these metabolites were greater in the environment of early spherical embryos such as uric acid, tryptophan, and tyrosine. Other metabolites were greater in the environment of later stage embryos (i.e., tubular) such as serine, phenylalanine, and phosphoric acid. These data illustrate several putative metabolites that change within the uterine milieu as porcine conceptuses transition between spherical, ovoid, and tubular conceptuses. Variation of these metabolites in unique patterns provide possible molecular signals necessary to initiate and progress embryos thru early stages of elongation.

Technical Abstract: The objective of this study was to identify metabolites within the porcine uterine milieu during the early stages of blastocyst elongation. At day 9, 10, or 11 of gestation, reproductive tracts of White crossbred gilts (n = 38) were collected immediately following harvest and flushed with Roswell Park Memorial Institute-1640 medium. Conceptus morphologies were assessed from each pregnancy and corresponding uterine flushings were assigned to one of five treatment groups based on these morphologies: 1) uniform spherical (n = 8); 2) heterogeneous spherical and ovoid (n = 8); 3) uniform ovoid (n = 8); 4) heterogeneous ovoid and tubular (n = 8); 5) uniform tubular (n = 6). Uterine flushings from these pregnancies were submitted for non-targeted profiling by GC-MS and UPLC-MS techniques. Unsupervised multivariate principal component analysis (PCA) was performed using pcaMethods and univariate ANOVA was performed in R with FDR adjustment. PCA analysis of the GC-MS and UPLC-MS data identified 153 and 104 metabolites, respectively. After FDR adjustment of the GC-MS and UPLC-MS data, 38 and 59 metabolites, respectively, differed (P < 0.05) in uterine flushings from pregnancies across the five conceptus stages. Some metabolites were greater (P < 0.05) in abundance for uterine flushings containing earlier stage conceptuses (i.e., spherical) such as uric acid, tryptophan, and tyrosine. In contrast, some metabolites were greater (P < 0.05) in abundance for uterine flushings containing later stage conceptuses (i.e., tubular) such as creatinine, serine, and urea. These data illustrate several putative metabolites that change within the uterine milieu during early porcine blastocyst elongation.