Role of Candidate Genes Regulating Uterine Prostaglandins Biosynthesis for Maternal Recognition of Pregnancy in Domestic Animals

The survivability and opportunity of successful development of an embryo are influenced directly or indirectly by factors controlling uterine microenvironment. Out of all factors, hormones such as prostaglandins (PGs) released during the preimplantation period influence molecular interactions involved in maintenance of pregnancy through reciprocal interactions between the conceptus and endometrium. PGs are important regulators of female reproductive functions, namely, ovulation, uterine receptivity, implantation, and parturition. Among different classes of PGs, prostaglandin F2α (PGF2α) and prostaglandin E2 (PGE2) are main prostanoids produced by human and bovine endometrium for successful growth and development of the posthatching blastocyst. In ruminants, PGF2α produced by endometrium is the major luteolytic agent, whereas PGE2 has luteoprotective and antiluteolytic properties. Therefore, the development and maintenance of the corpus luteum (CL), as well as establishment of pregnancy, depend on the balance of luteolytic PGF2α and luteotropic PGE2. In this review, we discussed the expression and function of genes which predominantly regulate the synthesis and their secretion of PGF2α and PGES, namely, PGFS (AKR1B5/AKR1C3), PGES, PGFR, and COX-2. 1. Introduction Successful embryo development and survival include formation of blastocyst, implantation into the uterus, formation of placenta, development of the heart, and vascularisation of both embryo and fetus to assist nutrient deliverance [1]. Among these developmental events, implantation of embryo is a crucial step and its success mostly depends on the efficiency with which the maternal recognition of pregnancy (MRP) is established [2, 3]. The MRP includes series of events that are synchronized by the endocrine interaction between the mother and the embryo. The majority of studies examining the molecular mechanisms of conceptus-endometrial interactions carried out during the peri-implantation period of pregnancy have focused on the maternal side, describing changes in the transcriptome of the endometrium [4, 5]. Major factor affecting gene expression in the endometrium is day of the estrous cycle/early pregnancy. In other words, irrespective of pregnancy status, the temporal changes in gene expression in the endometrium are similar in pregnant and cyclic animals up to the time of MRP [5, 6]. The survivability and opportunity of successful development of an embryo are influenced directly and indirectly by various paracrine and autocrine factors (steroid hormones, growth factors, and cytokines),