How endometrial secretomics can help in predicting implantation

The receptive endometrium represents a physiologic state of the uterus when embryo implantation is possible. It occurs at a discreet stage of the menstrual cycle referred to as window of implantation, outside of which the uterus is refractory to the initiation of pregnancy. In modern society, assisted reproductive technologies (ART) are an ever-growing demand to counter infertility; however, pregnancy rates remain below expectations, not least because current diagnostic tools fail to provide accurate assessment of endometrial receptivity. In the last decade, widespread arrival of large-scale analytical techniques has brought a stream of studies seeking to identify specific biomarkers of endometrial receptivity by extracting global molecular information from endometrial biopsies. The latter are an undesired requirement for dating the endometrium, which has prompted development of alternative strategies whereby large-scale analyses and non-invasive methods can converge. In this context, secretomics represents an attractive possibility to assess endometrial maturation and receptivity. Endometrial-cell secretions poured into the uterine cavity are suitable for collection and analysis without the need of biopsying, and might provide important additional molecular information reflective of endometrial physiology and day of cycle. If properly validated, the outgoing results would represent a step forward in the development of diagnostic tools to assess endometrial receptivity.