GIANT AND BINUCLEATE TROPHOBLAST CELLS OF MAMMALS

The cellular origin, structure, and function of trophoblastic giant ce lls (GC) and binucleate cells (BNC) are reviewed. Mammals in which the se cells have received the greatest attention include rodents, rabbits , and humans (GCs), and ruminants and equids (BNCS). In almost all cas es these cells arise from the cytotrophoblast. All are large cells and contain either two diploid nuclei (BNCs), multiple nuclei (human plac ental bed GCs), or single nuclei with amplified DNA content (rodent an d rabbit GCs). Giant and binucleate cells typically exhibit the capaci ty for migration or invasion, although the degree of migratory activit y varies between species. While most end up within, or at the interfac e with, endometrial tissue, in some instances the GCs or BNCs contribu te directly to the interhemal membrane of the placenta. Hormone produc tion is a property which most GC-BNC populations have in common. Lacto gen or gonadotropin has been documented in almost all cells of this ty pe examined to date, and in some animals they are also steroidogenic ( e.g., rats and sheep). In spite of some common features, both structur al and functional differences remain and it is suggested that use of t erms such as mononuclear giant cells, multinucleate giant cells, and b inucleate cells be continued rather than assuming that these cells are all members of a single trophoblastic subtype. (C) 1993 Wiley-Liss, I nc.