Influence of the corpus luteum on cumulus-oocyte complexes competence in equines.
Authors: Dubeibe-Marin D F, Borraez D F, Gomez-López D L, Velasco-Acosta D A
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Researchers examined whether the presence and location of the corpus luteum (CL) influences the quality and developmental potential of cumulus-oocyte complexes (COCs) harvested from equine ovaries, collecting paired ovaries at slaughter and categorising them by CL status: ipsilateral CL present (CL+), contralateral CL only (CL−), and no CL (NCL). Although fewer COCs were recovered from CL+ ovaries (2.0 versus 4.9 from NCL), the oocytes from CL+ ovaries demonstrated superior nuclear maturation rates post-maturation (58.3% reaching metaphase II compared to 42% in NCL), alongside significantly elevated intrafollicular progesterone concentrations (574 ng/mL versus 392 ng/mL in NCL). Gene expression analysis revealed that bone morphogenetic protein-15 in oocytes and growth differentiation factor-9 in cumulus cells were substantially upregulated in COCs from CL-bearing ovaries, suggesting a systemic endocrine influence rather than a purely local effect. These findings have implications for reproductive management and in vitro maturation protocols, indicating that the hormonal milieu created by an active CL enhances oocyte competence markers despite reducing follicle population, which may inform optimal timing for oocyte collection in assisted reproductive programmes and highlight progesterone's role in regulating developmental gene expression in equine reproduction.
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Practical Takeaways
- •Corpus luteum presence is associated with improved oocyte nuclear maturation competence in equine oocyte collection, suggesting timing of oocyte recovery relative to estrous cycle stage may impact assisted reproductive outcomes
- •Intrafollicular progesterone concentration correlates with markers of oocyte quality (BMP-15, GDF9), providing a potential biomarker for selecting optimal ovaries or collection timing in equine breeding programs
- •Although CL presence reduces total COC quantity recovered, the quality of oocytes obtained is enhanced, which may offset the lower numbers for in vitro fertilization or embryo production protocols
Key Findings
- •Ovaries with corpus luteum (CL+) yielded fewer COCs (2±0.9) compared to ovaries without CL (4.9±0.8), but higher metaphase II maturation rates (58.3% vs 42%)
- •CL+ group showed higher intrafollicular progesterone concentrations (574 ng/mL) compared to NCL group (392 ng/mL)
- •BMP-15 expression in oocytes and GDF9 expression in cumulus cells were significantly higher in COCs from animals with CL (both CL+ and CL-) versus NCL group
- •COCs from contralateral CL location (CL-) exhibited expanded cumulus morphology (74.4%) but maturation rates intermediate between CL+ and NCL groups