Intern
Supervisor: Mihaela Pavličev

Unit for Theoretical Biology, Department of Evolutionary Biology
University of Vienna

Abstract

Placentation is one of the most diverse mammalian processes, ranging from (ancestrally) highly invasive, as seen in primates and rodents, to a secondarily derived type in hoofed mammals, called epitheliochorial, which is generally regarded as non-invasive. The bovine placentation is characterized by the opposing fetal and maternal epithelial layers, which stay mostly intact, but also by trophoblast giant cells that can migrate into the maternal uterine epithelium to form fetomaternal synctia. To understand the non-invasive placentation of cows in more detail, we examined maternal (caruncles), fetal (cotyledons) and fetal-maternal (placentomes) tissue at 40-, 61-, 100- and 174-days (out of 285) of pregnancy. We focused on cytokeratin expression to localize epithelia and found cytokeratin-positive cells also in the uterine stroma. We show that trophoblast migration may be more invasive than previously assumed. We also observe a dynamic process of erosion and proliferation in the uterine epithelium of caruncles at different time points and narrow down the enucleation of fetal red blood cells to the first 60 days of pregnancy. Our results add to the current understanding of bovine placentation, proposing that trophoblast cells in cows are in fact invasive, namely to a degree that trophoblast invasion is not only limited to the uterine epithelium but can also reach the stroma. We see our results as a stepping stone to stimulate discussion and for further research investigating the role of trophoblast and epithelial cells in the bovine placenta.