Periimplantation mouse embryos and uterine tissues were examined by means of immunohistochemistry for their expression of the Ca2+ dependent cell‐cell adhesion molecules, E‐ and P‐cadherin. E‐cadherin was detected in all embryonic cells during periimplantation stages, and also detected in the uterine epithelium. When blastocysts attached to the uterine epithelium, E‐cadherin was detected at implantation sites between the mural trophectoderm and the uterine epithelium on 5 day of pregnancy. P‐cadherin was first detected in the mural trophectoderm on 4.5‐day blastocysts, and then detected in the ectoplacental cone, giant cells and visceral endoderm from 5.5 day. P‐cadherin was also detected in the maternal uterine decidual cells from 5.5 day. After degeneration of uterine epithelial cells, giant cells make direct contact with uterine decidual cells, and P‐cadherin was detected at contact sites between these cells. Thus, the complicated process of implantation seems to be supported by temporal and spatial expression of the multiple classes of cadherins.
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