Global analyses and potential effects of extracellular vesicles on the establishment of conceptus implantation during the peri-implantation period.

Intrauterine extracellular vesicles (EVs) are involved in establishing proper conceptus-endometrial communication, which is essential for conceptus implantation and subsequent successful placentation. Despite several studies on intrauterine EVs, the composition and quantitative changes in conceptus and endometrial EVs, as well as the effects of intrauterine EVs on endometrial epithelial cells (EECs) during the peri-implantation period, have not been well characterized. To elucidate global changes in proteins in EVs extracted from uterine flushings (UFs) during the pre-implantation (P17), just-implantation (P20), and post-implantation (P22) periods, the datasets of the proteome iTRAQ analysis were compared among P17, P20, and P22 EVs. These analyses revealed that the composition and function of proteins in the EVs changed dramatically during peri-implantation in cattle. Notably, intrauterine P17 EVs affected the high expression of "Developmental Biology" and "morphogenesis of an endothelium" compared with those in P20 and P22 EVs. Furthermore, P20 EVs had the functions of the high expression of "mitochondrial calcium ion homeostasis" and "Viral mRNA Translation" compared with those in P17 EVs. Transcripts extracted from EECs treated with P17, P20, or P22 EVs were subjected to RNA-seq analysis. These analyses identified 60 transcripts in EECs commonly induced by intrauterine EVs recovered from P17, P20, and P22, a large number of which were associated with "type I interferon signaling pathway". Collectively, these findings reveal the presence and multiple functions of EVs that are potentially implicated in facilitating conceptus implantation into the uterine epithelium during the peri-implantation period.