Progress towards species-tailored approaches in reproductive biotechnologies

In the past four decades, the bovine model has been highly informative and inspiring to assisted reproductive technologies (ART) in other species. Most of the recent advances in ART have come from studies in cattle, particularly those unveiling the importance of several processes that must be recapitulated in vitro to ensure the proper development of the oocyte. The maintenance of structural and functional communications between the cumulus cells and the oocyte and a well-orchestrated chromatin remodeling with the gradual silencing of transcriptional activity represent essential processes for the progressive acquisition of oocyte developmental competence. These markers are now considered the milestones to design physiological approaches to increase the efficiency of reproductive technologies. Different in vitro approaches have been proposed. In particular, the so-called "prematuration" is a step performed in culture before in vitro maturation to support the completion of the oocyte differentiation process. Although these approaches did not lead to astonishing improvements, they currently represent a proof of principle that allows the design of tailored in vitro strategies for developing competent oocytes in several species, including humans. An advancement in ART's efficiency would be desirable in carnivores, where progress is limited. This review highlights the critical aspects that should be considered to extend the experience gained in cattle to carnivores. Comparative studies in multiple animal species are crucial to progress in reproductive medicine. They are essential for building a unifying framework of oocyte biology to boost fertility performance in the breeding system, biodiversity preservation, and translational medicine.