Unique Aspects of Human Placentation

Abstract

Human placentation differs from that of other mammals. A suite of characteristics is shared with haplorrhine primates, including early development of the embryonic membranes and placental hormones such as chorionic gonadotrophin and placental lactogen. A comparable architecture of the intervillous space is found only in Old World monkeys and apes. The routes of trophoblast invasion and the precise role of extravillous trophoblast in uterine artery transformation is similar in chimpanzee and gorilla. Extended parental care is shared with the great apes, and though human babies are rather helpless at birth, they are well developed (precocial) in other respects. Primates and rodents last shared a common ancestor in the Cretaceous period, and their placentation has evolved independently for some 80 million years. This is reflected in many aspects of their placentation. Some apparent resemblances such as interstitial implantation and placental lactogens are the result of convergent evolution. For rodent models such as the mouse, the differences are compounded by short gestations leading to the delivery of poorly developed (altricial) young.

Regulation of human trophoblast gene expression by endogenous retroviruses

“…Placental development and structure displays wide variation across eutherian species, even within the primate order (Carter and Enders, 2004). Notably, the deep interstitial trophoblast invasion observed in humans is unique to great apes (Carter, 2021). Placentas differ in cellular composition, histological arrangement and gross morphology, as well as many molecular aspects, all of which shape interactions between conceptus and mother, and their outcomes.…”

CITED2 is a Conserved Regulator of the Uterine-Placental Interface

“…Placentation provides a means for the fetus to grow and develop in the female reproductive tract 1,2 . The structure of the mammalian placenta exhibits elements of species specificity [73][74][75][76] . However, it is also evident that there are conserved features associated with the regulation of placental development and placental function 3,12,74 .…”

“…Placentation provides a means for the fetus to grow and develop in the female reproductive tract 1,2 . The structure of the mammalian placenta exhibits elements of species specificity [77][78][79][80] .…”

Selenoproteins in the Human Placenta: How Essential Is Selenium to a Healthy Start to Life?

“…During the first trimester, the placental intervillous space is low in oxygen as trophoblast cells plug the tips of uteroplacental spiral arteries, limiting supply of oxygenated maternal blood [ 102 ]. At the end of the first trimester, these plugs degrade, followed by a second wave of trophoblast invasion, and an increase in placental oxygen partial pressure triggering oxidative stress in trophoblasts [ 103 ]. This sharp rise in oxidative stress in the trophoblast is associated with the onset of maternal blood circulation in the placenta, where ROS act as a signalling molecule that contributes to trophoblast invasion and vascular development in the placenta [ 18 ].…”