Placental contribution to the endocrinology of gestation and parturition.

Gerhard Schuler,Rainer Fürbass,Karl Klisch

doi:10.21451/1984-3143-ar2018-0015

Abstract

In addition to many other functions, the placenta is a source of a vast number of autocrine, paracrine and endocrine factors. However, the spectrum of placental regulatory factors, their concentrations, gestational profiles and roles may differ considerably even between phylogenetically closely related species. Depending on the species, placental regulatory factors of a broad range of molecule classes have been found including (glyco-)proteins, peptides, steroids and prostaglandins. Local placental regulatory factors are especially important for the dialogue between the fetal and the maternal compartment immediately at the feto-maternal borderline and for the control of growth, differentiation and functions of the placenta itself. Moreover, placental hormones in a proper sense may also have effects in more remote targets within the maternal compartment, serving functions such as pregnancy-specific adaptations of maternal circulation, provision of hemotrophe to the fetus or the development and function of the mammary gland. Functions of placental hormones in the fetus proper are less clear but may be especially important before the establishment of a functional fetal endocrine system and near term within the highly species-specific networks of signals preparing and initiating parturition. This review takes a comparative view on the situation in different domestic animals focusing on ruminants and on placental hormones occurring at significant concentrations in the maternal circulation.

Highlights

There is probably no other organ which shows such a structural diversity comparable to that of the placenta (Leiser and Kaufmann, 1994; Wildman et al, 2006)
The placenta anchors the fetus in the maternal uterus, induces the local immunotolerance preventing rejection of the fetal allograft, provides oxygen and nutrients originating from the maternal compartment and disposes fetal waste products
In the ovine pregnant uterus, two different ways have been identified for the production of prostaglandins at the onset of parturition, a cortisol-dependent/estrogen-independent mechanism within the trophoblast leading to the rise in fetal plasma PGE2, and a mechanism stimulated by placental estrogens within the maternal endometrium bringing about the massive release of prostaglandins considered relevant for myometrial activity (Whittle et al, 2000)

Summary

Introduction

There is probably no other organ which shows such a structural diversity comparable to that of the placenta (Leiser and Kaufmann, 1994; Wildman et al, 2006). Different from the situation in species with a prepartal progesterone withdrawal initiating rather single-stranded chains of events, in humans it has been suggested that the onset of birth results from a protracted parallel destabilization of pregnancy in several compartments of the fetal-placental-maternal unit synergizing in the transformation of the uterus from a quiescent to a contractile phenotype (modular accumulation of physiological systems; Mitchell and Taggart, 2009).

Results

Conclusion