No abstract

Tight junctions between luminal epithelial cells of the human uterus were studied by freeze-fracture electron microscopy. It was found that junctional complexity decreased during the menstrual cycle, and we explore how this finding may contribute to the role of the uterus in facilitating implantation.

Eleven endometrial biopsies, taken from six Turner's syndrome patients receiving hormone replacement therapy prior to treatment by oocyte donation and embryo transfer, were assessed by freeze fracture followed by electron microscopy for epithelial tight junctions. Nine of the eleven biopsies had no discernible tight junctions; the other two biopsies had reduced and disorganized junctional structures. Two patients subsequently became pregnant following embryo transfer. It is concluded that compromised epithelial integrity does not prevent embryo implantation in the human, an observation that is consistent with a barrier role for the epithelium except at times when appropriately conditioned with oestrogen and progesterone to induce receptivity for implantation.

An antiserum to rat neutrophils was raised and used to follow the distribution of endometrial neutrophils during the peri-implantation period. Uteri from four pregnant and four pseudopregnant rats killed at 14:00, 17:00, 20:30 and 23:00 h on day 5 of pregnancy and 09:00 h on day 6 were sectioned. Four sections from each of four implantation sites and four intersites from each rat were immunostained. There was wide variability among rats in the number of endometrial neutrophils, but a nested analysis of variance showed significantly fewer neutrophils at implantation sites than at intersites from 20:30 h onwards. This difference was primarily due to the presence of more neutrophils in intersite regions of the endometrium. The results from this study do not support a role for neutrophils in the implantation-associated increase in microvascular permeability or decidualization in rats.