Maternal-embryo interaction in the bovine oviduct: Evidence from in vivo and in vitro studies.

Assisted reproductive technologies have provided a very useful tool for studying early embryonic development. The exchange of signals between the embryo and maternal environment during this period is critical to successful development, but most mechanisms involved remain to be elucidated. Understanding how the mother communicates with gametes and embryos is a major scientific challenge but in vivo studies are difficult to perform, especially in cattle, since they are expensive, the amount of material is limited, and it is not possible to differentiate between the outcome of fertilization and early embryonic death. In addition, the local interactions of the embryo with the maternal epithelium may not be detectable because of the small size of the embryo and the difficulty of identifying its exact position in the oviduct. On the basis of current knowledge gained from in vivo studies, the challenge now is to identify appropriate in vitro models to facilitate the study of early embryo-maternal communication.