Expanded equine cumulus-oocyte complexes exhibit higher meiotic competence and lower glucose consumption than compact cumulus-oocyte complexes.

The research focuses on studying the differences in meiotic competence and glucose metabolism between compact and expanded equine cumulus-oocyte complexes (COCs). The results indicate that expanded COCs show higher maturity rates and lower glucose consumption compared to their compact counterparts, implying critical metabolic and genomic differences between the two.

Objective of the research

• The primary aim of the study was to investigate the differences in competence and glucose metabolism between compact (cCOC) and expanded (eCOC) equine cumulus-oocyte complexes. These differences were hypothesized to play a key role in the shape and behavior of the cCOCs and eCOCs. The experiment aimed to uncover glucose consumption patterns, expression of genes related to glucose transport, pyruvate and lactate production, glycolysis, apoptosis, and meiotic competence among these cells.

Procedure and results

• Compact and expanded COCs and mural granulosa cells (EC and CC respectively) were matured in vitro for 30 hours. At the end of this period, various metrics, including maturation rate, glucose metabolism, and gene expression, were evaluated.
• eCOCs showed a significantly higher maturity rate (50%) compared to cCOCs (21.7%). The glucose consumption was lower for eCOCs (1.8±0.5 nmol per COC) than for cCOCs (27.9±5.9 nmol per COC), indicating a different metabolic pattern.
• Similarly, pyruvate and lactate production was also comparably lower in eCOCs versus cCOCs.
• The study didn’t observe much difference in glucose consumption in EC and CC types, suggesting a similar metabolic response to glucose.
• Expression of the hyaluronan-binding protein (TNFAIP6) was higher in eCOCs and EC. The eCOCs also showed increased SLC2A1 expression.
• Evaluation of glycolysis-related enzymes didn’t reveal any significant differences between the COC or mural granulosa cell types. Similarly, no difference was found in the expression of SLC2A3.

Conclusions and implications

• The research demonstrated that expanded and compact cumulus-oocyte complexes in equine ovary exhibit distinct metabolic and genomic differences.
• It was revealed that eCOCs have a higher meiotic competence and a distinct glucose metabolism pattern compared to cCOCs, which might influence their functionality or response to various conditions.
• Further studies can explore these differences in more detail and understand the exact mechanisms behind these variations. This might help to deepen the understanding of equine reproduction and may open new avenues for therapeutic interventions in equine reproductive disorders.