Efeito da exposição ao estradiol prévia à progesterona sobre a expressão genica uterina em éguas receptoras acíclicas

Abstract

Positive correlation between estrus duration and subsequent pregnancy rate has already been demonstrated in cyclic recipient mares, and at the molecular level, higher endometrial expression of uterocalin (P19) and lower expression of fibroblast growth factor 2 (FGF-2) have been reported after progesterone (P4) treatment in mares previously subjected to long period of estradiol treatment. However, it is still unclear whether, associated with the different effects of hormonal treatments on the endometrium, if the presence or absence of an embryo in the uterus, would also affect the expression of genes that are possibly involved in uterine/conceptus interaction. Therefore, the objective of this study was to evaluate the endometrial expression of genes P19, FGF-2, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 1 receptor (IGFR-1), estrogen receptor α (ESR1), and progesterone receptor (PGR) in 23 anestrous recipient mares subjected to three hormonal protocols with different periods of exposure to estrogen (Long Estrus, 7 days in a total of 8mg; Short Estrus, 2 days with a unique dose of 2,5mg) or absence of estrogen (No Estrus), prior to administration of long-acting P4 (P4 LA; day 0). 28 embryos were transferred four days after administration of P4 LA, with 7 been to the LE group, 8 for the SE and 13 to the NE group. After 48 hours, with means on day 6, the attempt to recover the embryo was performed, along with uterine biopsies collection, regardless of whether the recovery was positive or negative. Evaluation of gene expression was performed via RT-qPCR. P19 and IGF-1 was upregulated, 1,4 and 2,9 times respectively, in the Long Estrus group compared to No Estrus group (P<0.05), and FGF-2, IGFR-1, and PGR showed lower expression ( at least 2,9, 1,5 and 2,3 times respectively) in the estrogen groups versus the No Estrus group (P<0.05). Regarding the attempt at embryonic recovery on D6, regardless of the presence or absence of an embryo, there was no difference (P<0.05) in gene expression between groups. In conclusion, uterine exposure to estrogen prior to progesterone elevation, with or without an embryo, seems to provide a better uterine environment, in terms of P19, FGF-2, IGF-1, and PGR gene expression, for the initial survival and development of the equine conceptus.