ABSTRACT
The most profound changes in the relationship of the trophoblast to endometrial tissues
occur in the first 5 days after the initiation of implantation. Not only have the
earliest stages-adhesion and epithelial penetration-never been seen in the human,
but also the trophoblastic plate and lacunar stages that follow are not available
for modern investigative methods. Studies of appropriately timed endometrium and of
trophoblast- and endometrium-derived cell lines have important implications for aspects
of implantation. Use of nonhuman primates and other animal models for appropriate
stages in implantation could further our understanding of direct trophoblast-uterine
interactions. The mechanisms involved in epithelial penetration by infiltration of
the syncytial trophoblast into the uterine luminal epithelium could be studied profitably
using the marmoset or the ferret. Drawing of the blastocyst into an interstitial location
might be investigated in the guinea pig. Formation of trophoblastic lacunae can be
investigated in the cynomolgus monkey. By using such animal models of events of implantation
in situ, implications concerning the molecules involved in adhesion, penetration of
junctional complexes, and uterine vessel invasion that have been derived from in vitro
or murine studies may be placed in context.
KEYWORD
