E-cadherin, a Ca(2+)-dependent cell adhesion molecule, is necessary for endometrial receptivity to blastocyst implantation. The aim of this study was to investigate the differential expression of E-cadherin in canine uterus during early pregnancy and its regulation under different conditions by in situ hybridization. E-cadherin mRNA expression was at a low level in the glandular epithelium on days 6, 12 and 17 of pregnancy. On days 20 and 23 of pregnancy, E-cadherin mRNA was highly expressed in the glandular epithelium surrounding the embryo, but not in the luminal epithelium and declined in villi and placenta on day 28 of pregnancy. During oestrous cycle, a moderate level of E-cadherin mRNA expression was found in the luminal and glandular epithelium of canine uteri at oestrus stage. The same expression was also found at anoestrus stage. Progesterone slightly induced the expression of E-cadherin mRNA in the luminal and glandular epithelium of ovariectomized canine uterus. These results suggest that E-cadherin expression is closely related to canine implantation and can be up-regulated by progesterone.
