Tanya D. Burrows

Expression of adhesion molecules by endovascular trophoblast and decidual endothelial cells: implications for vascular invasion during implantation.

Summary During the process of implantation, maternal spiral arteries within the decidua are invaded by trophoblast cells that adhere to and migrate along the luminal surface of the vascular endothelial cells. This phenomenon resembles the events that occur during the migration of neutrophils into an acute inflammatory site, therefore it is possible that similar mechanisms are involved. Indeed, previous observations have shown that endovascular trophoblast expresses the blood group-related antigen sialyl Le x . In this study, we show, by immunohistology, the expression of both E- and P-selectin by vascular endothelial cells only in the decidua basalis and not in decidua parietalis. In contrast, ICAM-1 is expressed by all vascular endothelium throughout the decidua. Expression of VCAM-1 is variable at the implantation site, and is not expressed by vascular endothelial cells in decidua parietalis. Interestingly, we demonstrate the strong expression of a polysialylated form of NCAM by endovascular trophoblast. Our data suggests that vascular invasion by trophoblast is regulated by the expression of appropriate adhesion molecules which permit interaction between endovascular trophoblast and decidual endothelial cells.

Uterine NK cells and trophoblast HLA class I molecules.

PROBLEM: To investigate the proposal that NK cells in decidua may control trophoblast migration during implantation of the human placenta.

Functions of Human Decidual NK Cells

The main population of lymphocytes found in the human decidua during early pregnancy are NK‐like cells with a distinctive phenotype, CD56bright CD16− CD3−. These cells are in close association with invading trophoblast that may be their in vivo target. We have examined three aspects of decidual NK function in vitro: cytotoxicity, proliferation, and cytokine production. The functional assays indicate uterine lymphocytes differ fundamentally from both PBL and even from classical circulating NK cells. Their role in the establishment of normal pregnancy remains unknown.

Role of Decidual Large Granular Lymphocytes/Natural Killer Cells in Human Implantation

Human placental implantation involves invasion of the uterus by placental trophoblast cells. The extent of this invasion is tightly controlled. Insufficient invasion will lead to inadequate blood supply to the fetoplacental unit, and overextensive invasion will result in placenta percreta (1). The mechanisms that control this trophoblast invasion are not known. The decidua is likely to provide an important element of this control because implantation over areas deficient in decidua, such as over a previous cesarean section scar or in the fallopian tubes, generally shows a significantly greater degree of trophoblast invasion. It is unclear, however, which component of the decidua is important in this regard.