Phagocytic properties of cultured murine trophoblast.

Abstract

The phagocytic potential of cultured trophoblast from early (ectoplacental cone (EPC); day 7.5 post coitum) and mid-term (placenta; day 12 to 14 post coitum) pregnancy in the mouse has been examined using a variety of test particles and culture conditions. In suspension, small numbers (less than 1 per cent) of large placental trophoblast cells showed limited phagocytic uptake of Staphylococcus aureus but not of opsonized sheep red blood cells (RBCs). In contrast, trophoblast phagocytosis was never seen in monolayer placental cell culture. Placental macrophages consistently exhibited phagocytic uptake of both opsonized sheep RBCs and S. aureus under these conditions. In monolayer culture, EPC trophoblast phagocytosed S. aureus, but there was only limited uptake of RBCs (mouse or sheep) or spermatozoa. When cultured in a three-dimensional matrix (blood and plasma clots), however, EPC trophoblast demonstrated extensive phagocytosis of both RBCs and sperm. These results are discussed with reference to the use of in vitro systems for examining developmental processes, and a possible role for trophoblast phagocytosis in early gestation is proposed.