Gene expression of WNTs, β-catenin and E-cadherin during the periimplantation period of pregnancy in pigs--involvement of steroid hormones.

WNTs (wingless-type MMTV integration site family, member) are morphogenes considered as important factors taking part in uterus developmental processes and implantation. β-catenin is a downstream effector of WNTs action within the cell as well as, through E-cadherin, affecting epithelial organization and function. This study was conducted to investigate WNT4, WNT5A, WNT7A, β-catenin (CTNNB1) and E-cadherin (CDH1) gene expression and protein localization in the endometrium during the periimplantation period. Furthermore, the effect of 17β-estradiol (E(2)) and progesterone (P(4)) on WNTs, CTNNB1 and CDH1 gene expression in the porcine endometrium in vitro was examined. WNT4 protein was localized in the luminal and glandular epithelium as well as in the basal lamina of the uterine mucosa. WNT5A protein was detected only in the luminal epithelium. WNT7A, β-catenin and E-cadherin protein were identified both in the luminal and glandular epithelial cells, however, WNT7A protein immunoreactivity varied during respective days of estrous cycle and/or pregnancy. Despite unchanged expression of WNT4 mRNA in the endometrium of cyclic and early pregnant pigs, the negative influence of E(2) on WNT4 gene during in vitro experiment was observed. WNT4 and CDH1 gene expression was negatively correlated with blood plasma E(2) and P(4) level in uterine luminal flushings (ULFs) on Day 12 of pregnancy. Expression of WNT5A gene was up-regulated in the endometrium on Day 9 of pregnancy when compared to the respective day of the estrous cycle. A significant decrease of WNT7A gene expression and increase of CDH1 mRNA amount was detected on Day 12 of pregnancy. Overall, the results show the spatial localization of WNT4, WNT5A, WNT7A, β-catenin and E-cadherin proteins in porcine endometrium during periimplantation period of pregnancy and indicate significant changes of WNT5A, WNT7A and CDH1 gene expression before implantation in the pig.