CYTOLOGICAL ASPECTS OF VASCULAR INVASION BY THE TROPHOBLAST OF CALOMYS CALLOSUS IN HEPATIC TISSUES

Ectoplacental cones isolated from embryos on the seventh day of pregna ncy were transplanted beneath the hepatic capsule of recipient adult a nimals to document the morphological patterns of vascular invasion by the trophoblast in the absence of the maternal environment and the inf luence of its peculiar vasculature. Females, and females and males of Calomys callosus, a cricetid rodent, were used, respectively, as embry o donors and recipient animals. Three to 5 days later, the grafted reg ions were excised and processed for light and electron microscopy. Inv asion of the liver parenchyma by the trophoblast progressed along the vascular beds, associated with gradual phagocytosis of hepatic cells, greatly favoring the morphological characterization of invasive steps exhibited by the trophoblast to access the different kinds of vessels, to trespass the various vascular components and the different levels of the surrounding hepatic parenchyma. It is possible that either in u tero during the establishment of embryomaternal circulation in early p regnancy or ex utero under experimental conditions, the trophoblast ex hibits similar vascular invasion behavior. In view of this, our findin gs may contribute to a belter understanding of trophoblast cell migrat ion to the maternal blood supply as well as the role of the trophoblas t in the establishment of the placental circulation during pregnancy. (C) 1995 Wiley-Liss, Inc.