On Trophoblastic Binucleate Cells, Feto-maternal Interactions At Implantation And The Definitive Ruminant Placenta.

Abstract

The origin of syncytial cells found within the uterine epithelial layer in ruminants has been a subject of much investigation and in the cow and sheep the evidence suggests that they are formed as a result of the migration and fusion of trophoblastic binucleate cells with uterine epithelial cells (Wathes & Wooding, 1980; Wooding, 1984). In the goat, controversy still exists as to the origin of these giant cells; one group of investigators has suggested that they are formed by lateral fusion of individual uterine epithelial cells (Lawn, Chiquoine & Amoroso, 1969; Dent, 1973) whereas another contends that they develop as a result of migration and fusion of trophoblastic binucleate cells with maternal uterine epithelial cells (Wooding et al. 1986; Lee, Wooding & Brandon, 1986a). In order to define more clearly the role of various cell types in early placental formation in the goat, changes occurring in the cotyledons during initial stages of pregnancy and implantation (14 to 23 days post coitum [dpc]) were examined. Particular attention was directed at finding morphological evidence for either lateral fusion of uterine epithelial cells and/or migration and fusion of binucleate cells with uterine epithelial cells. Improved fixation and staining techniques were employed in order to obtain good preservation of the structural relationships between the trophoblast and uterine epithelium.