Uso de fluido ovidutal sintético (SOF) como meio único na produção in vitro de embriões (PIVE) bovinos

Abstract

In vitro embryo production (IVEP) has become one of the main reproductive biotechnologies, with Brazil recognized as the world’s largest producer of embryos. IVEP consists of three main stages: in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro culture (IVC), which traditionally require different culture media to meet the specific metabolic demands of gametes and embryos at each stage. The aim of this study was to evaluate the efficiency of using Synthetic Oviduct Fluid (SOF) as a single medium for IVM, IVF, and IVC by analyzing cumulus cell expansion, nuclear maturation, lipid droplet content, cleavage and blastocyst production rates, and the expression of genes related to metabolism (SCD1, SREBF1 and SLC2A1), oxidative stress (GPX1, SOD1, SOD2 and CPT1B), apoptosis (CASP03, BCL2 and BAX), and embryo implantation (VEGF). Ovarian follicles obtained from a local slaughterhouse were aspirated, and cumulus–oocyte complexes (CCOs), classified as grades I to III, were selected and randomly allocated into two experimental groups: a Control group, using conventional media for IVM (TCM-199 supplemented with hormones and 10% fetal bovine serum) and IVF (TALP), and an SOF group, in which SOF-based media were used for IVM (SOF-IVM supplemented with hormones and 10% fetal bovine serum) and IVF (SOF-IVF). Cumulus cell expansion was evaluated before and after maturation. After IVM, a subset of oocytes was subjected to Sudan Black staining for lipid content assessment and Hoechst staining for nuclear maturation analysis and mitochondrial intensity analysis by MitoTracker Red CMXROs fluorescence, while the remaining oocytes were used for IVF and IVC to assess embryo development and the expression of 11 target genes in the resulting blastocysts. Oocytes matured in SOF medium showed higher nuclear maturation rates to metaphase II (p = 0.01), lower degeneration rates (p = 0.05) and lower mitochondrial intensity (p < 0.0001), although greater cumulus cell expansion was observed in the Control group (p = 0.001). The use of SOF did not affect oocyte lipid content (p = 0.39), cleavage rate (71% vs. 68.5%; p = 0.74), blastocyst production (23.6% vs. 20%; p = 0.54), or the molecular profile of embryos (p > 0.05). In conclusion, SOF used as a single culture medium throughout all stages of in vitro embryo production is a viable alternative to conventional media, maintaining oocyte competence, embryo development, and molecular markers associated with embryonic production.