Extracellular Vesicles: Modulators of Embryo Maternal Interaction in the Bovine Model

Abstract

Embryo-maternal communication during preimplantation development plays a fundamental role in the establishment and maintenance of pregnancy in mammals. This communication is key in early development and is regulated by signaling pathways between the oviduct, uterus, and embryo. Extracellular vesicles (EVs) are a way of intercellular communication between the maternal reproductive tract and the embryo. EVs are small particles naturally released from cells to communicate with other cells. Therefore, the objective of this study was the validation of the optimal conditions for the establishment of an ex vivo model of embryo-maternal communication (co-culture of embryos on oviductal and endometrial explants) by evaluating the viability of oviductal and endometrial explants and embryos, as well as their ability to excrete EVs into the culture medium. For this, oviductal and endometrial explants were exposed to different culture conditions: 6 and 18 hours of incubation in Synthetic Oviductal Fluid (SOF) and Roswell Park Memorial Institute (RPMI) media. In parallel, embryos at ≥8 cells stage (day 2.5) and at blastocyst stage (day 7) were cultured under the same conditions. Regarding the culture of explants, the results did not show differences in the ability to secrete EVs to the medium regardless of the media and time of incubation. However, the viability of both oviductal and endometrial explants was compromised after 18 hours of culture. In addition, no differences in terms of development and embryonic quality were found. Finally, we could not detect EVs secreted by the embryos using our methodology. It can be concluded that the culture for 6 and 18 hours in SOF and RPMI does not affect the capability of the explants to secrete EVs nor embryo survival. However, it is necessary to optimize both the isolation methodology of embryonic EVs and the processing of the Explants.