Dynamic regulation of intercellular junctions is an essential aspect of many developmental, reproductive, and physiological processes. We have shown that expression of the desmosomal protein desmoplakin decreases in the luminal uterine epithelium during the preimplantation period of pregnancy in mice. By the time of implantation (between Days 4.5 and 5 of pregnancy), desmoplakin protein can barely be detected by SDS-PAGE and Western blotting, and by immunocytochemistry, it is restricted to well-spaced, punctate dots at the apicolateral junction. Using confocal XZ series and electron microscope quantitation, both the density and distribution of desmosomes along the lateral cell surfaces of luminal epithelial cells were observed to change during early pregnancy. On Day 1 of pregnancy, desmosomes were found at high density in the apicolateral junctional complex, being present here in 79% of ultrathin sections examined, whereas on Day 5, the density was much reduced (present in only 18% of ultrathin sections examined). Desmosomes were found along the lateral surfaces, at or below the level of the nucleus, in 15% of ultrathin sections examined on Day 1 of pregnancy but in only 1% on Day 5. Desmoplakin mRNA declined during the first 4-5 days of pregnancy, along with the protein, suggesting that these changes are controlled at the level of mRNA. This study shows that desmosomes are regulated during early pregnancy, and we propose that a reduction in desmosome adhesion facilitates penetration of the luminal epithelium by trophoblast cells at implantation.
The carbohydrate H-type-1 antigen has been implicated in attachment of the murine blastocyst to the endometrial epithelium. Monoclonal antibody 667/9E9 was used to investigate the steroidal dependency of expression of this antigen in the murine endometrial epithelium using intact or ovariectomized mice treated with oestrogen or the pure anti-oestrogen, ICI 182,780. The effects of this anti-oestrogen were also investigated in the endometrial epithelium from intact rats. In both ovariectomized, oestrogen-supplemented and intact mice after treatment with ICI 182,780, staining with monoclonal antibody 667/9E9 was abolished in the luminal epithelium on both the apical and lateral cell surfaces, whereas basal staining remained. Glandular staining in mice was not affected in the same manner. In intact rats, where H-type-1 antigen expression has been reported to be predominantly controlled by progesterone, the anti-oestrogen had little effect, in accordance with previous reports.
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