Blastocyst implantation in the chinese hamster (Cricetulus griseus)

Abstract

Embryonic development of the Chinese hamster (Cricetulus griseus) was studied from the onset of implantation to the formation of the parietal yolk sac placenta. Implantation began on day 6 of pregnancy, when the embryo became fixed to the uterine luminal epithelium. At this time there was no zona pellucida, and microvilli of the trophoblast and uterine epithelium were closely apposed. Stromal cells immediately adjacent to the implantation chamber began to enlarge and accumulate glycogen. By day 7 the mural trophoblast penetrated the luminal epithelium in discrete area. The trophoblast appeared to phagocytize uterine epithelial cells, although epithelium adjoining the points of penetration was normal. In other areas nascent apical protrusions from the uterine epithelium indented the surface of the trophoblast. The epiblast had enlarged and both visceral and parietal endoderm cells were present. The well-developed decidual cells were epithelioid and completely surrounded the implantation chamber. On day 8 the uterine epithelium had disappeared along the mural surface of the embryo. The embryonic cell mass was elongated and filled the yolk sac cavity. Reichert's membrane was well developed. The uterine epithelial basal lamina was largely disrupted, and the trophoblast was in direct contact with decidual cells. Primary and secondary giant trophoblast cells were present and in contact with extravasated maternal blood. The mural trophoblast formed channels in which blood cells were found in close proximity to Reichert's membrane. Decidual cells were in contact with capillary epithelium and in some cases formed part of the vessel wall. Structural changes occurring in the embryo and endometrium during implantation in the Chinese hamster are described for the first time in this report and are compared to those described for some other myomorph rodents.

Penetration of the uterine epithelial basement membrane during blastocyst implantation in the mouse

“…In sites from both delayed and normally implanting mouse blastocysts, decidual cells also penetrated the basement membranes of stromal vasculature and were in contact with endothelial cells and contents of the lumen. Similar activity was seen in the rat (Welsh and Enders, 1987) and Chinese hamster (Blankenship et al, 1990) during implantation. Decidual cells lining the stromal vasculature in the rat are eventually replaced by trophoblast (Welsh and Enders, 1987).…”

Uterine receptivity and the plasma membrane transformation

“…In another rodent species, the Chinese hamster, Blankenship et al [21] found that attachment is quite similar to that in the rat with extensive remodelling of microvilli into irregular protrusions of the plasma membrane and Winterhager and Denker [22] also reported flattening and loss of microvilli in the rabbit. Potts and Racey [23] reported loss of apical microvilli and flattening of the apical plasma membrane in bats during early pregnancy such that uterine epithelial and trophoblast membranes ran parallel and Oliveira et al [24] have more recently reported on membrane flattening in bats.…”

Loss of laminin and type IV collagen in uterine luminal epithelial basement membranes during blastocyst lmplantation in the mouse

“…x 55. blast tissue from different species is clearly capable of extracellular matrix catabolism, as indicated by several lines of research (Salomon and Sherman, 1975;Glass et al, 1983;Fisher et al, 1985Fisher et al, ,1989Yagel et al, 1988). The evidence for decidual cell penetration of basement membrane strongly suggests that these cells can also modify this matrix (Schlafie et al, 1985;Blankenship et al, 1990;Blankenship and Given, 1992). Additionally, results of the present study indicate that loss of laminin and type IV collagen in luminal basement membrane was closely correlated with the mesometrial extent of decidual cell development, with basement membrane lost from areas not in contact with trophoblast tissue.…”