Expression of occludin in mouse uterus during estrous cycle and periimplantation period.

Abstract

In an effort to define the molecular structure of tight junction (TJ) and possible influence of ovarian steroids on the development of TJ in the endometrium, the expression of occludin was examined in the mouse uterus during the estrous cycle and early pregnancy period. We also investigated the effect of 17beta-estradiol (E2) and progesterone (P4) on occludin mRNA level in ovariectomized (OVX) mouse uterus. In normal cyclic mice, occludin mRNA level was the highest at proestrus stage and the lowest at metestrus stage. Coincidently, occludin immunoreactivity was largely found in apical region of plasma membrane together with moderate signal in basolateral region of luminal and glandular epithelia. The most intense signal was found at diestrus stage and gradually decreased until metestrus stage. Stromal occludin immunoreactivity was also found and the signal was the highest at estrous stage. During early gestation period occludin expression was gradually decreased from gestation day (GD) 1 to 6. At GD 6, occludin was down-regulated at the implantation sites compared to interimplantation sites. In stroma occludin immunoreactivity was increased around the implanting embryos, suggesting altered paracellualr barrier property of the implantation site. In OVX mice uterus E2, P4 or E2+P4 treatment significantly increased occludin mRNA level and occludin immunoreactivity in stroma was markedly increased. Taken together, this suggests that molecular architecture and spatial distribution of TJ in the endometrium cyclically change during estrous cycle and early pregnancy period under tight control of ovarian steroids in the mouse uterus. (poster)