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AAPH-treated blastocysts vs CTL-treated blastocysts

ABSTRACT: In order to understand how in vitro culture affects embryonic quality, we analyzed survival and global gene expression in bovine blastocysts after exposure to increased oxidative stress conditions of IVC. A pro-oxidant agents that act extra-cellularly by promoting ROS production (0.01 mM 2,2'-azobis (2-amidinopropane) dihydrochloride [AAPH]) was added from days 3 to 7, and transcriptomic analysis was then performed in resulting blastocysts. Precisely, after in vitro maturation and fertilization, bovine zygotes were culture in vitro in normal condition, then at day 3, embryos were allocated into culture in control or supplemented with AAPH (0.01 mM) until day 7. At this time, blastocysts were harvested and analyzed. Our hypothesis was that AAPH treatment will affect blastocyst survival and gene expression associated with low embryo quality

ORGANISM(S): Bos taurus

PROVIDER: GSE42279 | GEO | 2012/11/14

SECONDARY ACCESSION(S): PRJNA179525

REPOSITORIES: GEO

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Project description:Differentiation of totipotent embryonic cells into the first cell lineages (trophectoderm (TE) and inner cell mass (ICM), and further into epiblast (EPI) and primitive endoderm (PE)), although well studied, is only beginning to be understood at the molecular level. An in depth understanding of the regulation of these early differentiation events would enable improvements in the quality of in vitro produced embryos, as well as the study and application of bovine embryonic stem cells. The objective of this work was to perform single cell RNASeq on bovine blastocysts derived in vivo (IVV), in vitro in a conventional in vitro production system (IVC), and in vitro in reduced nutrient media (IVR). All in vitro culture was serum free. In vivo embryonic cells could be assigned based on Leiden clustering analysis, although there was some overlap in expression of marker genes. The two TE groups identified clearly separated in a uniform manifold approximation and projection (UMAP) plot from EPI groups. Putative epiblast cells could be identified. In in vitro embryos produced in a conventional system, considerable overlap in expression of marker genes made Leiden clustering difficult, but a selected count could be used for UMAP to tentatively identify one TE, 2 EPI and 2 PE groups. In assigned cell types we observed higher expression of the identifying marker genes, but some marker genes were expressed in all cell types. In IVC embryos, TE markers clustered while PE and EPI marker genes overlapped. In IVR embryos, again there was considerable overlap between marker gene expression. Like IVC embryos, TE was easily identified by clustering in IVR, but EPI and PE were too similar to distinguish. In summary, the methods used here could partially distinguish putative cell types in bovine blastocysts, although marker gene expression was not always discreet. This may not be surprising given differentiation events are in progress in the blastocyst stage embryo. TE cells were more easily distinguished than EPI and PE cells, which would support this hypothesis.

Project description:Metabolic stress associated with negative energy balance in high producing dairy cattle and obesity in women is a risk factor for decreased fertility. Non-esterified fatty acids (NEFA) are involved in this pathogenesis as they jeopardize oocyte and embryo development. Growing evidence indicates that maternal metabolic disorders can disturb epigenetic programming, and more specifically DNA methylation, in the offspring. Final oocyte maturation and early embryo development coincide with specific methylation changes and both time periods are sensitive to adverse environments. Therefore, we investigated whether elevated NEFA concentrations affect the establishment and maintenance of DNA methylation patterns in oocytes and embryos and subsequently alter transcriptomic profiles and developmental competence of the resultant blastocysts. To do this, bovine oocytes and embryos were exposed to different NEFA concentrations in two separate experiments. In the first experiment, oocytes were matured in vitro for 24 hours in medium containing: 1) physiological (âBASALâ) concentrations of oleic (OA), palmitic (PA) and stearic (SA) or 2) elevated (pathophysiological or âHIGH COMBIâ) concentrations of OA, PA and SA. In the second experiment, zygotes were cultivated in vitro for 6.5 days under BASAL or HIGH COMBI conditions. The developmental competence was evaluated by assessing cleavage and blastocyst rate. Overall gene expression and DNA methylation of resultant blastocysts were analyzed using microarray techniques. Data regarding DNA methylation were re-evaluated by pyrosequencing. HIGH COMBI-exposed oocytes and embryos displayed a lower competence to develop into blastocysts compared to their BASAL-exposed counterparts (19.3 % compared to 23.2 % and 18.2 % compared to 25.3 %, respectively) (P < 0.05). HIGH COMBI-exposed oocytes and embryos resulted in blastocysts with altered DNA methylation profiles and transcriptomic fingerprints, compared to BASAL-exposed counterparts. Differences in gene expression and methylation were more pronounced after exposure during culture compared to maturation suggesting that zygotes are more susceptible to an adverse environment. Main gene networks affected were related to lipid and carbohydrate metabolism, cell death, immune response and metabolic disorders. This may offer clues regarding the high rate of embryonic loss and metabolic diseases during later stages of life observed in offspring from mothers displaying lipolytic disorders. Two experiments were set up to characterize the epigenomic profile of the resultant day 7.5 blastocysts. In the first (in vitro maturation or IVM) experiment, the effect of elevated NEFA exposure during oocyte maturation (24 h) on DNA methylation profiles was evaluated by exposing oocytes to the BASAL or HIGH COMBI conditions. In the second (in vitro culture or IVC) experiment, the effect of elevated NEFA exposure during embryo culture (6.5 days) on DNA methylation marks was evaluated by exposing embryos to the BASAL or HIGH COMBI conditions. A total of 1039 and 1412 oocytes were used in the IVM and IVC experiment, respectively, equally distributed between treatments in 4 replicates. Resultant day 7.5 blastocysts were snap frozen for subsequent DNA methylation analysis (80 blastocysts in each experiments, equally collected between treatments in 4 replicates).

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AAPH-treated blastocysts vs CTL-treated blastocysts

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