SELECT

Early reproductive events in mammals are still not properly understood. As a result, in cattle breeding, pregnancy failures amount to 40% before 7 days of gestation. Spermatozoa (spz) on their way to the oocyte undergo a drastic selection procedure, must acquire their fertilizing ability and survive until ovulation occurs: all these events, as well as fertilization, take place in the oviduct lumen in presence of oviductal fluid microflows. In the isthmic part of the oviduct, a fraction of the sperm population binds to epithelial cells, forming a "functional sperm reservoir", while other spz go directly to the fertilization site. In vitro studies have identified molecular players involved in the spz-oviduct interactions and reported a positive impact of these interactions on sperm viability and capacitation. However, current in vitro models do not recapitulate the complex physiology of the oviduct, with its different parts, differentiated/functional epithelial cells and microflows. Next, the role of the spz-oviduct interactions remains poorly understood: does the sperm reservoir select the best spz to fertilize to yield a viable embryo or, conversely, does it trap the worst ones? Does spz binding to the reservoir trigger a molecular and functional response of the oviduct? What is the impact of this response on subsequent embryo development? The SELECT project aims to answer these questions by using for the first-time, innovative bovine oviduct organoids cultured in a microfluidic device to incorporate microflows. SELECT brings together two INRAE units specialized in early bovine reproductive events and the Applied Microfluidics for BioEngineering Research laboratory of the University of Twente (the Netherlands) for their expertise in microfluidics, focusing on reproductive biology. Ultimately, SELECT will generate new knowledge which is essential to improve the longevity of farm animals and develop new strategies for the conservation of animal biodiversity.