Uterine secretomics: a window on the maternal-embryo interface

The analysis of endometrial secretions offers a window on human peri-implantation events that have hitherto been difficult to study noninvasively. Uterine secretomic analysis provides a sensitive means of interrogating the contents of secretions, which have been shown to play a key role in determining endometrial receptivity and embryo-endometrial signaling, and in providing a nourishing environment to the preimplantation embryo. Compared with other means of assessing the endometrium with genomics or proteomics, secretomics offers a nondisruptive approach, allowing analysis during conception cycles. It also provides information on the downstream molecular profile directly encountered by the embryo, offering an integrated review of the complete endometrial surface rather than information representative of only a discrete biopsy site. In this article, recent data derived from uterine secretomics are reviewed. In addition to in vivo studies, recent data from in vitro studies that are changing our understanding of the role of the endometrium in embryo selection are reviewed. Finally, the role of uterine secretions in nutrition and early development programming of the embryo is considered.