Meiotic arrest, resumption and TZP retraction in bovine COCs undergoing pre-IVM: lessons from a refined GV stage classification

Autor(es)

Saraiva, Helena Fabiana Reis de Almeida ; Sangalli, Juliano Rodrigues ; Alves, Luana ; da Silveira, Juliano Coelho ; Meirelles, Flavio Vieira ; Perecin, Felipe

• Tipo de documento: Artigo Científico
• Fonte: Reproduction; v. 169, n. 5, p. 16-pg., 2025-05-01.

Resumo

In brief Oocytes with subtle differences in chromatin configuration and nuclear lamina characteristics, detectable by a refined germinal vesicle (GV) classification system here described, respond differently to meiotic maturation systems leading to different in vitro maturation (IVM) outcomes.Abstract The nuclear, cytoplasmic and molecular maturation of the mammalian oocyte is a finely orchestrated sequence of events that relies on proper cumulus-oocyte communication. Bovine oocytes enter the IVM systems at the GV stage exhibiting four different chromatin configurations (GV0-GV3). Herein, we associate the oocyte chromatin and nuclear lamina configurations to propose a refined GV classification (GV0, GV1.1-GV1.3, GV2.1-GV2.3 and GV3.1-GV3.3). This refined GV classification system was correlated with oocyte meiosis resumption and transzonal projections (TZPs) density of cumulus-oocyte complexes (COCs) submitted to three IVM systems (control IVM and a modified IVM preceded or not by a pre-IVM step). Pre-IVM resulted in lower polar body extrusion rates at 19 h IVM, albeit similar to 24% of the oocytes extruded their first polar body at 9 h IVM. Pre-IVM sustained 80% of oocytes meiotically arrested but altered GV distribution, reducing GV2 and increasing GV1.3 and GV3.3 categories. Pre-IVM reduced TZP densities predominantly in pre-matured GV3 and GVBD COCs. At 9 h of IVM, both groups matured in modified IVM showed lower TZP densities compared to immature and IVM control. Gene expression supports the TZP density differences, with ERK2 and PRKACA upregulation in pre-matured cumulus and in modified IVM groups at 9 h of IVM. GDF9 and BMP15 levels were similar between treated and control groups at all time points. Our findings indicate that despite the IVM system, the initial oocyte GV stage influences pre-IVM and IVM outcomes. The refined GV classification system is a useful tool to oocyte biologists. (AU)

• Processo FAPESP: 13/08135-2 - CTC - Centro de Terapia Celular
• Beneficiário: Dimas Tadeu Covas
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs
• Processo FAPESP: 21/09886-8 - Maturação epigenética do oócito e totipotência: o potencial do oócito e sua relação com o nicho folicular ovariano
• Beneficiário: Lawrence Charles Smith
• Modalidade de apoio: Auxílio à Pesquisa - Programa SPEC
• Processo FAPESP: 22/01433-7 - EMU concedido no processo FAPESP 21/06645-0 : Microscópio Biológico Invertido Thunder Imager 3D Assay
• Beneficiário: Juliano Coelho da Silveira
• Modalidade de apoio: Auxílio à Pesquisa - Programa Equipamentos Multiusuários
• Processo FAPESP: 21/08759-2 - Mensagens armazenadas no gameta masculino bovino: efeitos do estresse térmico, papel das interações epidídimo-espermatozoide e contribuição paterna ao desenvolvimento embrionário
• Beneficiário: Felipe Perecin
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 21/06645-0 - Vesículas extracelulares como uma plataforma para diagnóstico e manipulação do sistema de produção in vitro de embriões: a nova geração da reprodução animal
• Beneficiário: Juliano Coelho da Silveira
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores - Fase 2