Immunohistochemical localization of glutaredoxin and thioredoxin in human endometrium: a possible association with pinopodes.

The human endometrium is only receptive for blastocyst implantation during a short period of the menstrual cycle. Pinopodes have been suggested to be markers of uterine receptivity, but little is known about their function and the biochemical processes taking place in them. In this study, we have examined the presence of glutaredoxin (Grx) and thioredoxin (Trx) and their co-localization with pinopodes in the normal human endometrium. Endometrial biopsies were obtained from fertile women with normal menstrual cycles. The biopsies were examined by scanning electron microscopy for detection of pinopodes and by immunohistochemistry for the expression of Grx and Trx. The pinopodes showed strong immunostaining for Grx. Increasing levels of Grx immunoreactivity were seen in the luminal and glandular epithelial cells concomitant with pinopode formation. Trx immunostaining was most intense in the ciliated cells of the luminal and glandular epithelium, while the staining was moderate to strong in a majority of the other cells, both epithelial and stromal. Trx levels did not change during the secretory phase of the cycle. The intense immunostaining concomitant with the presence of pinopodes suggests that Grx plays an important role during implantation, possibly by protecting the epithelial cells from apoptotic actions of the trophoblast cells.