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Sex steroid hormones are major regulators of uterine and placental growth and functions, as well as many other biological processes. To examine the mRNA expression of nuclear estrogen (ESR1 and 2) and progesterone (PGRAB and B) receptors in different compartments of the uterus and placenta, tissues were collected in experiment 1 on days 16, 20, and 28 after natural mating (NAT) and on day 10 after estrus (nonpregnant controls [NP]); and in experiment 2 on day 22 of NAT, and pregnancies established after transfer of embryos generated through mating of FSH-treated ewes (NAT-ET), in vitro fertilization (IVF), or in vitro activation (parthenotes). In experiment 1, ESR1 expression in endometrial stroma (ES), endometrial glands (EGs), and myometrial blood vessels (MBVs), ESR2 in endometrial blood vessels (EBV), PGRAB in ES, and PGRB in ES, EG, and MBV was greater in pregnant than NP ewes depending on the day of pregnancy. The day of pregnancy affected the expression of ESR1 in MBV, ESR2 in EBV and MBV, and PGRAB in ES. In experiment 2, ESR1, PGRAB, and PGRB in EG, but not in other compartments, was greater in NAT-ET than NAT, and PGRB was greater for NAT-ET than IVF. These data demonstrate that ESR and PGR expression differ in pregnant versus NP ewes in selected compartments and was affected by pregnancy stage or embryo origin in selected utero-placental compartments. Thus, sex steroid hormone mRNA expression is differentially regulated in a spatiotemporal manner in the uterus and placenta and is affected by the application of assisted reproductive technology in sheep., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Uteroplacental development is a crucial step facilitating conceptus growth. Normal placental development comprises extensive placental angiogenesis to support fetoplacental transport, meeting the metabolic demands of the fetus. Compromised pregnancies due to maternal stressors such as over or undernutrition, maternal age or parity, altered body mass index, or genetic background result in altered vascular development of the placenta. This negatively affects placental growth and placental function and ultimately results in poor pregnancy outcomes. Nonetheless, the placenta acts as a sensor to the maternal stressors and undergoes modifications, which some have termed placental programming, to ensure healthy development of the conceptus. Sex steroid hormones such as estradiol-17β and progesterone, chemokines such as chemokine ligand 12, and angiogenic/vasoactive factors such as vascular endothelial growth factors, placental growth factor, angiopoietins, and nitric oxide regulate uteroplacental development and hence are often used as therapeutic targets to rescue compromised pregnancies. Interestingly, the presence of sex steroid receptors has been identified in the fetal membranes (developing fetal placenta). Environmental steroid mimetics known as endocrine disrupting compounds disrupt conceptus development and lead to transgenerational impairments by epigenetic modification of placental gene expression, which is another area deserving intense research efforts. This review attempts to summarize current knowledge concerning intrinsic and extrinsic factors affecting selected reproductive functions with the emphasis on placental development., (Copyright © 2016 Elsevier Inc. All rights reserved.)