238. Claudins and occludin in the rat endometrium

Abstract

Regulation of the uterine luminal environment is important for the successful attachment and implantation of the blastocyst. Tight junctions regulate the paracellular pathway between epithelial cells lining the uterine lumen and the uterine glands. The aims of this present study was firstly to establish the presence and cellular distribution of claudins and occludin in the luminal epithelia during early pregnancy using immunofluorescence microscopy and deconvolution, and secondly to determine the influence of ovarian hormones on their expression. Occludin and claudins -1, -3, and -4 were present in luminal epithelium. Occludin and claudin-4 showed increased expression in luminal epithelium at the time of implantation, whereas claudin-1 and -3 expression remained the same throughout early pregnancy. In ovariectomised rats administered ovarian hormones, occludin and claudin-4 showed increased expression in luminal epithelium in progesterone-dominant regimes and decreased expression when administered oestrogen alone. Expression of claudin-1 and -3 in luminal epithelium was not effected by ovarian hormones. Claudin-2 was not expressed during early pregnancy nor in ovariectomised rats. In conclusion, these results show that occludin and claudins -1, -3 and -4 are present in luminal and glandular epithelium, and provide the permeability properties needed to separate the luminal and the stromal environment at the time of implantation. Furthermore, occludin and claudin-4 expression is controlled by ovarian hormones being upregulated by progesterone.