Inclusion of exosomes derived from follicular fluid during pre-maturation of bovine oocytes with NPPC: effects on maturation and oocyte competence

Abstract

Oocyte maturation is regulated by several mechanisms that act together in the cumulus-oocyte complex (CCO) included in the ovarian follicle. However, the in vitro culture of oocytes causes an imbalance of regulatory agents, resulting in lower efficiency and quality of the oocytes. Methods that temporarily block meiotic maturation in vitro may mimic some of the follicular signals that occur in vivo, which may provide a better condition for the oocyte to complete cytoplasmic and nuclear maturation, including accumulating transcripts and proteins that will be essential for subsequent embryonic development. In the present work, we will evaluate the efficiency of the type C natriuretic peptide (NPPC) on the maintenance of gap junction functionality and maintenance of chromatin compaction in a configuration in which some transcriptional activity still occurs (GV0 and GV1). In addition, extracellular vesicles (exosomes) obtained from the fluid of ovarian follicles at different times of the follicular wave will be added in the pre-maturation (pre-IVM) system proposed here. It is expected that the eventual incorporation of exosomes into the CCOs will further increase the amount or type of transcripts in the oocyte or surrounding cumulus cells. In this way, the accumulation of transcripts in the cumulus cells or oocyte will be investigated, aiming to evaluate the effectiveness of the treatment on the greater accumulation of gene transcripts related to oocyte quality and the acquisition of the competence for the embryonic development. As the practical implication of this proposal is the increase in embryo production, the final evaluation of this study will be the determination of the effectiveness of the proposed pre-IVM strategy on the outcomes and quality of blastocysts produced, determined by the evaluation of the number of blastomers and apoptosis rates. (AU)