Can the interaction of extracellular vesicles with the cumulus-oocyte complex during pre-maturation and in vitro maturation influence oocyte competence and epigenetic regulation?

• Grant number: 23/16602-1
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: March 01, 2024
• End date: February 28, 2026
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Cláudia Lima Verde Leal
• Grantee: Priscila Helena dos Santos
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Associated scholarship(s): 25/09646-8 - Pre-maturation culture system: the association of dbcAMP and sildenafil as meiotic arrest modulators to improve oocyte maturation and embryo production, BE.EP.PD

Abstract

Epigenetic mechanisms that govern the ability of the female gamete (the oocyte) to become totipotent are at the heart of many unanswered questions in biology. A better understanding of these basic phenomena offers the opportunity to develop new biotechnologies with benefits for humans and animals. This proposal is part of the São Paulo Excellence Chair (SPEC-FAPESP) thematic project "Epigenetic maturation of the oocyte and totipotency - oocyte potential and its relationship with the ovarian follicular niche". The aims of this study are to investigate temporary and reversible meiotic arrest (pre-IVM) before in vitro maturation (IVM), as a way to provide additional time for the cumulus-oocyte complex (COC) to acquire epigenetic and molecular characteristics that lead to greater oocyte competence. Supplementation with extracellular vesicles from follicular fluid (fEVs), constituents of the follicular niche (environment), during the culture steps will also be investigated. For this purpose, in Part 1 (PMI/MI), experiment 1, the oocytes will be subjected to PIVM followed by IVM and, before and after each step, they will be evaluated for: 1) nuclear maturation, 2) epigenetic patterns (DNA and histones), expression of imprinted genes and 4) embryonic development by parthenogenetic activation. In Part 2 (fEVs), experiment 1, the addition of fEVs during PIVM/IVM will be evaluated for: 1) nuclear maturation and oocyte quality (mitochondrial activity, lipid content, amount of mtDNA, lipid metabolism and mitochondrial function transcripts, and levels of ROS and GSH) and 2) expression of antioxidant and expansion genes in cumulus cells (CC). In experiment 2, the effect will be determined on: 1) transcriptome (RNAseq of oocytes and CC) and 2) epigenetic patterns in oocytes. In experiment 3, the effect on competence for development after in vitro fertilization and culture will be determined and the embryos evaluated for: 1) quality (total cell number and apoptosis), 2) epigenetic patterns and 3) expression of epigenetic regulation genes. It is expected to obtain new knowledge that will help to understand the epigenetic regulation in oocytes and its relationship with fEV, providing bases for improvements in the conditions of in vitro embryo production.