Are embryonic metaboloepigenetics profiles dependent on culture media viscosity when cultured in the oviduct-on-a-chip device?

Abstract

The existence of early embryomaternal communication already in the oviducts has been for too long underestimated. It is observed that the oviducts are cyclically prepared to receive a pregnancy in each estrous cycle, but when the embryo is indeed present, it is now known that a two-way communication is established between the oviductal cells and the embryo. Even though this communication exists and has been demonstrated by many studies, many questions are still not answered. One significant limitation obtaining this information is the access to the oviduct in situ. In these circumstances, three-dimensional (3-D) systems have become valuable tools for understanding oviductal physiology. Among the 3-D systems, there is the "oviduct-on-a-chip", a 3-D printed device with a tubular like insert that can be combined with microfluidics. However, when applied for pre-implantation embryo development, the cleavage and embryo rates were lower than expected. This outcome might be related to a specific dynamic microfluidic system feature, the shear stress. On the other hand, the presence of this feature in microfluid devices is desired, since it naturally exists in the oviduct lumen. Therefore, the lower embryo rate production could be related to inappropriate shear stress and not its existence, which means it needs to be adjusted. One way to modulate shear stress is by changing the culture media viscosity. Therefore, we hypothesize that by modifying the culture media viscosity in the "oviduct-on-a-chip" device, we will improve the shear stress caused in the embryos and, consequently, obtain a model to culture oviductal cells more similar to the tissue and better to study the early embryomaternal communication. With this in mind, our objective is to determine if modulating the culture media viscosity can improve embryomaternal communication. To evaluate the effect of this communication in embryo development, we elected the metabolism and epigenetic embryonic profiles as the target of our analyses, this choice was made based on the fact that these are the most important events that occur during the bovine embryo journey inside the oviductal lumen. To do that, culture media viscosity will be modulated using sodium alginate, a non-embryotoxic modulator of fluid viscosity which has the same property as the natural oviductal fluid (non-Newtonian). The present proposal will be divided into three experiments: 1) define the sodium alginate concentration for the embryo culture medium, 2) adapt the embryo culture medium viscosity when co-culture with bovine oviduct epithelial cells (BOEC), and 3) evaluate the effectiveness of viscosity modulation in the "oviduct-on-a-chip" when embryo and BOEC are co-cultured. (AU)