Cytological aspects of trophoblast‐uterine interaction in early implantation

Abstract

Abstract Trophoblast‐uterine epithelial cell interrelationships were studied using implantation sites from the rat, rabbit, guinea pig, armadillo, bat and ferret. It was found that in all species trophoblast cells extend over several epithelial cells at the apposition stage of implantation. Trophoblast can adhere to the apical ends of uterine epithelial cells by primitive junctional complexes. More surprisingly, in most species desmosomal junctions are formed between trophoblast and the lateral aspects of uterine epithelial cells by primitive junctional complexes. More surprisingly, in most species desmosomal junctions are formed between trophoblast and the lateral aspects of uterine epithelial cells by primitive junctional complexes. More surprisingly, in most species forms the complementary protion of the apical junctional complexes with the adjacent luminal epithelial cells. Certain basement membranes appear to be barriers to trophoblast invastion in some species but not in others. There is little evidence that trophoblast is cytolytic, whereas all of the trophoblast examined gave some evidence of phagocytic activity, and the trophoblast of some of the more invasive forms showed evidence of being histolytic. It is suggested that the capacity of trophoblast to form junctions with epithelial cells is an important part of the implantation process, facilitating penetration of the endometrium without dislodgment of the blastocyst.