Uterine cellular changes during mammalian pregnancy and the evolution of placentation†.

There are many different forms of nutrient provision in viviparous (live-bearing) species. The formation of a placenta is one method where the placenta functions to transfer nutrients from mother to fetus (placentotrophy), to transfer waste from the fetus to the mother, and to perform respiratory gas exchange. Despite having the same overarching function, there are different types of placentation within placentotrophic vertebrates, and many morphological changes occur in the uterus during pregnancy to facilitate formation of the placenta.

Sex steroids influence the plasma membrane transformation in the uterus of the fat-tailed dunnart (Sminthopsis crassicaudata, Marsupialia).

The uterine epithelium undergoes remodelling to become receptive to blastocyst implantation during pregnancy in a process known as the plasma membrane transformation. There are commonalities in ultrastructural changes to the epithelium, which, in eutherian, pregnancies are controlled by maternal hormones, progesterone and oestrogens. The aim of this study was to determine the effects that sex steroids have on the uterine epithelium in the fat-tailed dunnart Sminthopsis crassicaudata, the first such study in a marsupial.

Uterine Epithelial Cells Undergo a Plasma Membrane Transformation During Early Pregnancy in the Domestic Cat (Felis catus).

Mammals exhibit similar changes in uterine epithelial morphology during early pregnancy despite having a diverse range of placental types. The uterine epithelium undergoes rapid morphological and molecular change ("plasma membrane transformation") during the early stages of pregnancy to allow attachment of the blastocyst. The domestic cat, Felis catus is in the order Carnivora; all species within the Carnivora studied so far develop an endotheliochorial placenta during pregnancy.

Uterine Receptivity in Merriam's Kangaroo Rat (Dipodomys merriami).

The uterine surface undergoes significant remodeling, termed the "plasma membrane transformation," during pregnancy to allow for implantation of the blastocyst and formation of the placenta in viviparous amniote vertebrates. Unlike other species within the superorder Euarchontoglires, which have a hemochorial (highly invasive) placenta, kangaroo rats (Dipodomys spp.) exhibit a less invasive endotheliochorial placenta.

Epithelial cadherin disassociates from the lateral plasma membrane of uterine epithelial cells throughout pregnancy in a marsupial.

The uterine luminal epithelium is the first site of contact between fetal and maternal tissues during therian pregnancy and must undergo specialised changes for implantation of the blastocyst to be successful. These changes, collectively termed the plasma membrane transformation (PMT), allow the blastocyst to attach to the uterine epithelium preceding the formation of a placenta. There are similarities in the morphological and molecular changes occurring in live-bearing eutherian species during the PMT studied so far.

Desmoglein-2 during pregnancy and its role in the evolution of viviparity in a marsupial (Sminthopsis crassicaudata; Dasyuridae).

Attachment of the blastocyst and formation of the placenta during pregnancy is dependent on structural and cellular changes occurring in the uterine epithelium and in particular to the plasma membrane of these uterine cells. Desmosome expression decreases during pregnancy in eutherians and some squamates, presumably allowing for remodeling of the uterine epithelium and invasion of the trophoblast during implantation. Marsupials are a distinct mammalian amniote lineage of viviparity, with a short implantation or attachment period and varying levels of invasive placentation.