Early human trophoblast development: from morphology to function

Abstract

Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the pre-implantation phase, formation of the morula is followed by internalization of blastomeres that differentiate into the pluripotent inner cell mass lineage, while the cells on the surface undergo polarization and differentiate into the trophectoderm of the blastocyst. The trophectoderm mediates apposition and adhesion of the blastocyst to the uterine epithelium. These processes lead to a stable contact between embryonic and maternal tissues, resulting in the formation of a new organ, the placenta. During implantation, the trophectoderm cells start to differentiate and form the basis for multiple specialized trophoblast subpopulations, all of which fulfilling specific key functions in placentation. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that adapt the uterine wall to progressing pregnancy. The composition of these trophoblast subpopulations is crucial for human placenta development and alterations are suggested to result in placenta-associated pregnancy pathologies. This review article focuses on what is known about very early processes in human reproduction and emphasizes on morphological and functional aspects of early trophoblast differentiation and subpopulations.

More Tools for Evaluating Decidual Artery Disease

“…Its appearing lining maternal vessels are not expected at the end of the gestation. Immunohistochemical protein expression profiling is as expected, positive for keratin 7 and negative for vascular antibodies such as CD31 and CD34 28 (Figure 3).…”

“…18 • Persistence of intramural endovascular trophoblast in the third trimester: it could be the same as thrombus or plugs of trophoblast. 8,28 Even though the Amsterdam Placental Workshop Group Consensus agreed on the evaluation of arterial alterations, whether in the membrane roll or basal plate, or both, in properly analyzed placental specimen, decidual vasculopathy is more prevalent in the decidua parietalis than in the decidua basalis. 10,31 Persistent parietal trophoblast lining, as a novel finding, requires monitoring and further research, especially in order to confirm observational consistency, as well as the possible role this alteration plays in the physiopathology of preeclampsia or how it is associated with some kinds of HDP.…”

“…27 There are also endovenous, endolymphatic and endoglandular extravillous trophoblasts. 28 Endovascular extravillous trophoblast acts as trophoblastic thrombus in arterial lumens and as parietal trophoblast that temporarily replaces or accompanies endothelial cells. Both processes mainly take place in the first and second trimesters of pregnancy.…”

“…A controversy revolves around the total replacement of endothelial cells and the trophoblasts that accompany them. 28 Some authors think complete remodeling is expected for the 20th week, 13 or around that time. 14 As pregnancy progresses, the process leads to thin-walled, vein-like arteries.…”

New immune horizons in therapeutics and diagnostic approaches to Preeclampsia

“…Placental syncytiotrophoblast (STBs) of the floating villi formed by the fusion of cytotrohoblasts (CTBs) are mainly associated with the exchange and transport processes, whereas the anchoring villi of the placental basal plate give rise to invasive extravillous trophoblast (EVT) that originates from trophoblast cell columns. [55][56][57] The floating villi grow proliferative upon attachment to the maternal decidua to form proximal cell column trophoblasts (pCCTs) that mature and develop and further differentiate into distal CCTs (dCCTs), eventually ceasing their mitotic activity. [58][59][60][61][62] EVTs are formed into the distal cell column.…”