EPIDERMAL GROWTH-FACTOR, VASCULAR ENDOTHELIAL GROWTH-FACTOR AND PROGESTERONE PROMOTE PLACENTAL DEVELOPMENT IN RAT WHOLE-EMBRYO CULTURE

The development and survival of rat embryos in whole-embryo culture is limited by the lack of any maternal blood circulation in a purely fet al placenta. If the resulting placental insufficiency could be overcom e for some time by an increase of the placental exchange area, a prolo nged culture period would result and facilitate the development of emb ryos. In the present study, several attempts to stimulate proliferatio n and growth of the fetal placenta were made by the addition of vascul ar endothelial growth factor (VEGF), epidermal growth factor (EGF) and progesterone to the culture medium. Rat embryos were routinely explan ted with their embryonic membranes at 10.5 days of gestation. Decidua, parietal yolk sac, Reichert's membrane and the layer of superficial t rophoblastic giant cells were removed. The explants were cultured and gassed continously for 24 h in rotating plastic tubes containing rat s erum, diluted to 50% with modified COON's F12 medium. Either of the tw o growth factors or progesterone were added to each culture tube and a control group was cultured without any factor. After the addition of each of these factors the stimulatory effect on placental growth was a ssessed by morphometric evaluation of several placental parameters fro m semithin cross-sections: On adding each of the factors the whole cro ss-sectional area of the placenta significantly increased, as did the area of the fetal placental mesenchyme. VEGF also increased the area o f the trophoblast, and the area of the blood vessels enclosed within t he trophoblast, by an average of 9.4% and 23.6%, respectively. Thus, V EGF treatment resulted in a measurable extension of the exchange area of the fetal placenta.