Abstract
The effect of soluble fractions derived from the placenta on the outgrowth and giant cell transformation of the ectoplacental cone (EPC) was investigated in vitro. EPCs taken from the fetal mice on day 7.5 post coitum (pc) were incubated with α-MEM-containing fetal calf serum (FCS) (FCS-α-MEM) for 24 hr. Then, the medium was exchanged with α-MEM alone, FCS-α-MEM, or α-MEM containing a crude extract from placental region on day 8.5, 10.5 or 12.5 pc (10 ml phosphate buffer/g placenta). Each EPC was continued to be incubated for 6 days, and the rate of EPC outgrowth and the number of trophoblastic giant cells (TGCs) were evaluated under a phase-contrast microscope. As a result, the administration of each placental extract significantly induced the cell spreading and TGC transformation of EPC as compared with the culture in α-MEM alone. The rate of cell-spreading rapidly increased on the 2nd day after incubation in the medium containing placental extracts. In particular, EPC outgrowth was more remarkable in the medium containing the 10.5-day placental extract than in the other media including FCS-containing medium. The number of transformed TGCs was also the largest in the 10.5-day medium among the groups examined. These results indicate that certain placental factors at mid-gestation, especially on day 10.5 pc, may facilitate the EPC differentiation.
