Oocyte competence and epigenetic regulation of cumulus-oocyte complexes after interaction with extracellular vesicles before and after in vitro maturation.

• Grant number: 25/04898-9
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2025
• End date: August 31, 2028
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Cláudia Lima Verde Leal
• Grantee: Cláudia Lima Verde Leal
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

The epigenetic mechanisms that render the oocyte competent for development are important issues in female gamete biology, and a better understanding of these basic phenomena offers an opportunity to improve biotechnologies with benefits for humans and animals. This project aims to use an oocyte competence study model, based on the induction of temporary and reversible meiotic arrest (pre-in vitro maturation, PIVM), to provide additional time for the interaction of cumulus-oocyte complex (CCO) cells with each other, and with components of the follicular niche before final in vitro maturation (IVM). Thus, it is proposed to use PIVM, and during this time and of IVM, to supplement follicular fluid extracellular vesicles (fEVs), constituents of the follicular niche, to investigate their contribution to the acquisition of epigenetic and molecular characteristics that improve oocyte competence. In phase 1 (PIVM/IVM), OO will be subjected to PIVM followed by IVM and, before and after each period, will be evaluated for: 1) nuclear maturation, 2) epigenetic patterns (DNA and histones), 3) imprinted gene expression, and 4) embryonic development by parthenogenetic activation. In phase 2, experiment 1, fEVs will be added during PIVM/IVM and assessed for effects on: 1) nuclear maturation and oocyte quality (mitochondrial activity, lipid content, mtDNA copy number, lipid metabolism and mitochondrial function transcripts, and ROS and GSH levels) and 2) transcript abundance of antioxidant and expansion genes in cumulus cells (CC) will also be evaluated. In experiment 2, the effects on 1) epigenetic patterns in oocytes and 2) transcriptome (OO and CC) will be determined. In experiment 3, developmental competence after fertilization and in vitro culture will be evaluated, and the embryos obtained will be assessed for: 1) quality (total cell number and apoptosis), 2) epigenetic patterns, and 3) epigenetic regulation gene expression. It is expected to obtain new knowledge about epigenetic regulation in oocytes and its relationship with fEVs, contributing to provide a basis for improving in vitro embryo production conditions. (AU)