The oocyte in vitro maturation (IVM) is the focus of research because of the limiting factors of this phase. Thus, to improve this phase, studies investigate the addition or compositing modulation of growth factors and/or their availability in culture medium, as Insulin-like Growth Factor (IGF). The proof of IGF importance is evident by the presence of its receptor (IGFR1) on oocyte and in several bovine embryo stages, as well as its stimulatory effect on oocyte maturation and embryo development in vivo and in vitro. The bioavailability of IGF is regulated by two mechanisms: IGFBPs (IGF binding proteins) and PAPPA (Pregnancy-Associated Plasma Protein A). The PAPPA is responsible to cleave IGF from IGFBPs, increasing IGF availability. Many studies investigating the effects of adding exogenous IGF-1 in IVM, however, the modulation of in vitro bioavailability of IGF has not yet been investigated and can be an additional strategy to study the effects of the IGF system on IVM. On this, the objective of this study is to investigate the effects of PAPPA adding to IVM on oocyte competence in cattle. For this, cumulus-oocyte complexes (COCs) from bovine ovaries from slaughterhouse will be matured with increasing doses of PAPPA (0, 1, 10 and 100 ng/mL) and available in cellular and molecular structure: oocyte nuclear maturation, apoptosis rate and gene expression. We expected that the addition of PAPPA during IVM, increase the bioavailability of IGF and thus the positive effect of this system will improve the bovine oocyte competence.
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