Comparative analysis of porcine endometrial transcriptomes during the implantation period.
Early gestation in mammals is a dynamic stage that requires synchronization of processes in both uterine and embryonic tissues. In pigs, two critical events-maternal recognition of pregnancy and implantation-occur between days 12 and 16 of gestation. During this period, embryos transform from spherical to filamentous forms and begin secreting estradiol (E2) and prostaglandin E2 (PGE2), which prolong the lifespan of the corpus luteum and sustain progesterone (P4) production. These hormones also redirect the secretion of prostaglandin F2a (PGF2a) into the uterine lumen, preventing its luteolytic effect. Around day 14, close apposition of the trophectoderm and uterine epithelial cells is observed, leading to the formation of interdigitating microvilli. Implantation in pigs is non-invasive and occurs gradually, relying on the production of cytokines, chemokines, and angiogenic factors by the endometrium. Proper synchronization of gene expression related to steroid hormones, integrins, and metalloproteinases in the uterus and trophoblast is crucial. This study used RNAseq to compare gene expression profiles in porcine endometrium between days 12–13 and 15–16 of pregnancy, analyzing differentially expressed genes (DEGs), long non-coding RNAs (DELs), and alternative splicing events (DAS). The results highlight the complexity of mechanisms regulating early pregnancy and the need for further research on their synchronization.