Preeclampsia is an important disease during pregnancy and causes significant maternal and fetal mortality and morbidity. Despite intense research efforts, the etiology and pathogenesis of the disease remain largely unknown.

Since placentas from preeclamptic patients are smaller than normal, and cytokine growth factors are suggested to be important in placental growth, the effects of macrophage-colony stimulating factor (M-CSF) on human trophoblast cells were examined. While term trophoblast cells did not respond to M-CSF, those from early trimester and choriocarcinoma cells showed enhanced growth after treatment. In addition, the serum level of M-CSF in hypertensive pregnant women at the second trimester were significantly lower than those of normal pregnant women. These data suggest possible roles of M-CSF in preeclampsia.

When M-CSF was administered to pregnant rats on days 8-11, rats had smaller placentas at day 12 and increased fetal resorption rate at day 20. The effects of interleukin-12 (IL-12) was also examined on days 8-11. While placental development was normal at both days 12 and 20, fetuses were significantly smaller at day 20.

To remedy the difficulties and dangers associated with obtaining human placentas, I characterized endovascular trophoblast cell behavior in pregnant rats. In normal pregnancy, rat trophoblast cells simulated all features of human endovascular trophoblast behavior including selective invasion into the spiral arteries, retrograde migration, embedding, and secretion of PAS-positive materials as well as IIphysiological changes," In pregnancy terminated with a certain type of spontaneous fetal resorption, defective endovascular trophoblast cell behavior was observed, which was similar to that reported in preeclamptic pregnancy.

Finally, the roles of cytoskeleton on trophoblast cell locomotion were investigated in vivo with a cytoskeleton-disrupting agent, cytochalasin B. This treatment impaired trophoblast cell invasion at day 12 and induced smaller fetuses at day 20, suggesting the importance of cytoskeleton in trophoblast movement.

In conclusion, the results suggest the importance of the use of appropriate specimens and endpoints in the study of pregnancy, and rats may serve as a suitable animal model for the study of endovascular trophoblast cell behavior with clinical relevance to preeclampsia.