Endocrine, paracrine, and autocrine placental mediators in labor

Abstract

considering that preterm birth accounts for about 6-10% of all births in Western countries and of more than 65% of all perinatal deaths, elucidation of the particularly complicated mechanisms of labor is essential for determination of appropriate and effective therapeutic interventions. Labor in humans results from a complex interplay of fetal and maternal factors, which act upon the uterus to trigger pathways leading gradually to a coordinated cervical ripening and myometrial contractility. Although the exact mechanism of labor still remains uncertain, several components have been identified and described in detail. Based on the major role played by the human placenta in pregnancy and the cascade of labor processes activated via placental mediators exerting endocrine, paracrine, and autocrine actions, this review article has aimed at presenting the role of these mediators in term and preterm labor and the molecular pathways of their actions. some of the aforementioned mediators are involved in myometrial activation and preparation and others in myometrial stimulation leading to delivery. In the early stages of pregnancy, myometrial molecules, like progesterone, nitric oxide, and relaxin, contribute to the retention of pregnancy. At late stages of gestation, fetal hypothalamus maturation signals act on the placenta causing the production of hormones, including crH, in an endocrine manner; the signals then enhance paracrinically the production of more hormones, such as estrogens and neuropeptides, that contribute to cervical ripening and uterine contractility. These molecules act directly on the myometrium through specific receptors, while cytokines and multiple growth factors are also produced, additionally contributing to labor. In situations HORMONES 2012, 11(4):397-409 Review

Correlation of Oxytocin (OTR) and Estrogen Receptor (ER) mRNA in the Canine Placenta with the Detected Circulating Levels of Oxytocin and Estrogen during Pregnancy and Parturition

“…While the increasing concentration of estrogen stimulates the rise in uterine oxytocin receptors towards the initiation of labor in women and other animal species (Blanks et al, 2003;Spencer et al, 2004), we could not find a correlation between estrogen concentration and the expression of placental OTR mRNA. The placenta is considered to be one of the OT-synthesizing organs responsible for stimulating endometrial PGF2α production, resulting in luteolysis at the beginning of labor (Iliodromiti et al, 2012). In dogs, we could not show a link among estrogen concentration, the increase in placental oxytocin receptors at term pregnancy and the initiating of labor.…”

Women Serum Concentrations of the IL-10 Family of Cytokines and IFN-γ Decrease from the Third Trimester of Pregnancy to Active Labor

“…Although we emphasize the association between progesterone and serum cytokines concentrations, interactions among steroid hormones, hypothalamic-pituitary hormones, neuropeptides, growth factors, and cytokines should be also considered to understand the complex immunological response during active labor [47] . Specifically, a relevant hormone is prolactin (PRL), which has been proposed as a key hormone during delivery.…”

Bisphenol A Altersβ-hCG and MIF Release by Human Placenta: AnIn VitroStudy to Understand the Role of Endometrial Cells

“…This could explain the similar trend observed for these two markers. Under physiological conditions, the secretion of β -hCG is stimulated by estrogens, while it is inhibited by progesterone [58]. β -hCG promotes differentiation and invasion of the trophoblast and has immunomodulatory properties [21].…”