Modeling early embryo-maternal interactions in vitro

Abstract

Environmental conditions experienced during early embryonic development influence growth, metabolism, and gene expression of the embryo as well as the epigenetic profile of the offspring. The environment of the early embryo consists of the luminal fluid within the oviduct and uterus and the epithelial cells composing this fluid. Whether the embryo is able to shape its own microenvironment by interacting with the epithelial lining of the oviduct/uterus and which factors potentially interfere with or regulate these interactions remains to be elucidated. As early embryonic signals and the respective maternal responses are subtle and local events, it is challenging to study them in vivo. Therefore, adequate in vitro-models optimally mimicking the contact zone between the maternal reproductive tract and the early embryo are needed to a) elucidate basic mechanisms involved in early embryonic development and b) reduce the number of experimental animals used for such studies. Functional epithelial cells are generally defined by a polarized distribution of organelles and proteins. Proper polarization is tightly connected with physiological cell behavior and in vivo-like reactivity of the epithelium. Therefore, this review summarizes current strategies for in vitro preservation of epithelial cell polarity. It presents recent advances in 3D culture of female reproductive tract epithelia and embryo-epithelial cocultures. A special emphasis is set on compartmentalized culture systems, powerful tools for studying early embryo-maternal interactions in vitro. In such systems, cultured epithelial cells are manipulable from their basolateral as well as their apical cell pole, allowing concomitant application of embryonic as well as maternal effectors from the appropriate cellular compartment.