Advances in bovine oocyte in vitro maturation: mechanisms and strategies

In vitro maturation (IVM) of bovine oocytes remains a major limiting step in in vitro embryo production (IVP), largely because current culture systems fail to fully reproduce the dynamic biochemical and biophysical conditions of the follicular environment. Successful maturation requires precise coordination of nuclear and cytoplasmic events, supported by active communication between the oocyte and surrounding cumulus and granulosa cells. Intrinsic factors, including follicle size, metabolic status, mitochondrial function, and one-carbon metabolism (OCM), together with extrinsic elements such as hormonal cues, oxidative balance, and culture conditions, collectively determine oocyte competence. Among these, OCM plays a central role by regulating methyl donor availability, redox homeostasis, nucleotide synthesis, and epigenetic programming, thereby influencing early embryonic development. Recent advances aim to bridge the gap between in vivo and in vitro maturation. Strategies such as antioxidant supplementation, growth factor enrichment, and simulated physiological oocyte maturation (SPOM) have been reported to improve synchrony between nuclear and cytoplasmic maturation, although their effects remain variable across studies. Emerging technologies-including extracellular vesicle (EV) supplementation and microfluidic culture platforms-offer biomimetic environments that may enhance metabolic stability, restore physiological signaling, and improve embryo developmental potential. This review synthesizes current knowledge on the molecular and cellular mechanisms governing bovine oocyte maturation, critically evaluates intrinsic and extrinsic factors affecting IVM outcomes, and highlights innovative approaches that may increase oocyte competence and IVP efficiency. Overall, integrating omics-guided optimization, microfluidic systems, EV-based communication, and strengthened OCM pathways represents a promising yet still evolving direction for improving embryo yield and advancing sustainable cattle production.