Oocyte Maturation in Mammalian Species

Oocyte maturation encompasses a tightly coordinated progression from the germinal vesicle stage through metaphase II, entailing both nuclear and cytoplasmic events that prepare the female gamete for fertilisation and subsequent embryogenesis. Nuclear maturation is marked by chromatin condensation, breakdown of the germinal vesicle and extrusion of the first polar body under the control of maturation promoting factor. Cytoplasmic maturation involves redistribution of organelles, accumulation of maternal RNAs and proteins, and modification of the cytoskeleton to ensure correct spindle assembly and polar body formation. Surrounding cumulus cells and the extracellular matrix provide crucial paracrine support, mediated by hormonal cues such as follicle‐stimulating hormone and luteinising hormone, along with growth factors that activate signalling pathways including MAPK and PI3K–Akt. Species‐specific timing and microenvironmental requirements mean that protocols optimised for one mammal often require substantial adaptation for others. Advances in three‐dimensional culture systems, stem cell coculture and bioengineered scaffolds seek to recapitulate in vivo conditions and improve developmental competence, with direct implications for assisted reproduction, conservation of endangered species and fundamental studies of oocyte biology.

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Oocyte Maturation in Mammalian Species publication trend

The graph below shows the total number of articles in oocyte maturation in mammalian species across all publications each year (not limited to Nature Index journals).

Technical terms

In vitro maturation (IVM): Laboratory procedure inducing oocyte progression to metaphase II outside the ovarian follicle.

Germinal vesicle (GV): The oocyte nucleus prior to germinal vesicle breakdown and meiotic resumption.

Metaphase II (MII): The stage at which oocytes complete meiosis I, extrude the first polar body and await fertilisation.

Cumulus–oocyte complex (COC): The oocyte and its surrounding cumulus cells, which facilitate nutrient exchange and signalling.

3D culture system: A three-dimensional scaffold or microenvironment designed to better mimic in vivo follicular architecture.

Paracrine factors: Secreted molecules from neighbouring cells that act locally to regulate oocyte development.

References

1. IVM Advances for Early Antral Follicle-Enclosed Oocytes Coupling Reproductive Tissue Engineering to Inductive Influences of Human Chorionic Gonadotropin and Ovarian Surface Epithelium Coculture. International Journal of Molecular Sciences (2023).
2. Bovine in vitro oocyte maturation and embryo culture in liquid marbles 3D culture system. PLOS ONE (2023).
3. Effect of Passage Number of Conditioned Medium Collected from Equine Amniotic Fluid Mesenchymal Stem Cells: Porcine Oocyte Maturation and Embryo Development. International Journal of Molecular Sciences (2022).