Giant-Cell Transformation of Trophoblast Cells in Mice

During the early stages of pregnancy in the mouse, part of the trophectodermal cells undergo endoreplication and are transformed into trophoblastic giant cells (TGCs) that contain up to several hundred times the haploid amount of DNA per nucleus. TGCs, which position at the border between fetal and maternal tissues throughout mouse pregnancy, not only form the cell layer between fetal and maternal tissues, but they also secrete progesterone and several hormonal proteins structurally similar to prolactin and growth hormone. Thus, these cells play an important role in fetal-maternal interaction and tissue remodeling and function as endocrine cells essential for the maintenance of pregnancy. In this paper, we review current knowledge on the mechanisms of the TGC transformation of trophoblast cells and the biological function of TGCs in mouse placentation.