Abstract
The corpus luteum (CL) is a temporary endocrine gland vital for pregnancy establishment and maintenance. Estradiol-17β (E2) is the major embryonic signal in pigs supporting the CL’s function. The mechanisms of the luteoprotective action of E2 are still unclear. The present study aimed to determine the effect of E2 on luteal expression of factors involved in CL function. An in vivo model of intrauterine E2 infusions was applied. Gilts on day 12 of pregnancy and the estrous cycle were used as referential groups. Concentrations of E2 and progesterone were elevated in CLs of gilts receiving E2 infusions, compared to placebo-treated gilts. Estradiol-17β stimulated luteal expression of DNA-methyltransferase 1 (DNMT1), but decreased expression of DNMT3B gene and protein, as well as DNMT3A protein. Similar results for DNMT3A and 3B were observed in CLs on day 12 of pregnancy compared to day 12 of the estrous cycle. Intrauterine infusions of E2 altered luteal expression of the genes involved in CL function: PTGFR, PTGES, STAR, HSD17B1, CYP19A1, and PGRMC1. Our findings indicate a role for E2 in expression regulation of factors related to CL function and a novel potential for E2 to regulate DNA methylation as putative physiological mechanisms controlling luteal gene expression.
Highlights
We found a stimulating effect of E2 infused into the uterine lumen (33.3 μg of E2/infusion) on the luteal expression of the hydroxysteroid 17-beta dehydrogenase 1 (HSD17B1) gene (p < 0.05; Figure 4D), its expression remained unchanged in corpus luteum (CL) collected from gilts on day 12 of pregnancy or the estrous cycle (p > 0.05; Figure 4D)
The present report is the first evidencing the in vivo effect of the primary conceptus signal on the luteal expression of genes linked to processes pivotal for corpus luteum functioning in the pig
We indicated a new perspective for E2 to regulate the processes related to DNA methylation as possible physiological mechanisms controlling the expression of genes in porcine CLs
Summary
Pregnancy in mammals, including pigs, is a critical period that is dependent on molecular interactions between developing embryos and the maternal organism. At this stage, there is limited time during which the uterine luminal epithelium is favorable to blastocyst implantation, which has been defined as uterine receptivity [1]. Maternal recognition of pregnancy in the pig occurs between days 10 and 13 after fertilization [2] and during this period porcine conceptuses by secreting a plethora of factors to signal their presence in the reproductive tract (reviewed in [3]).
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