Bioscientifica Proceedings

The porcine conceptus undergoes rapid differentiation and expansion of its trophoblastic membranes between days 11 and 12 of gestation. The production of estrogen, the porcine embryonic pregnancy recognition signal, by the conceptus increases with trophoblast elongation. A complex interplay of estrogen signaling and prostaglandin (PG) metabolism in the endometrium finally results in prevention of luteolysis. Conceptus attachment to the uterine surface epithelium starts around day 14 of pregnancy preceded by a pronounced vascularization at the implantation zones, initiating the epitheliochorial placentation. To characterize the transcriptome changes in the porcine endometrium in the course of maternal recognition of pregnancy (MRP) and initial placentation, several transcriptome analyses using DNA microarrays and RNA sequencing (RNASeq) have been performed. This review summarizes and compares the results of these studies. Particularly, the studies where RNA-Seq has been used, revealed more than 2,500 and 1,900 differentially expressed genes (DEGs) for days 12 and 14 of pregnancy, respectively, in comparison to corresponding cyclic controls. Analysis of the results of these two studies revealed distinct differential gene expression, reflecting the different functions of the endometrium during these stages. The comparison of RNASeq and microarray data for day 14 of pregnancy revealed a good agreement of the results. Moreover, results of microarray studies investigating local responses of the uterine horn to embryos in the blastocyst stage and effects of premature exposure of pregnant gilts to exogenous estrogen on endometrium during early pregnancy are discussed and compared to the results from day 12 and day 14 of pregnancy.

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