New Insights into How Human Eggs Maintain Longevity Could Improve IVF Outcomes

Recent research has uncovered that human oocytes, or eggs, employ a minimalist cellular maintenance strategy to preserve their integrity over decades. Published in The EMBO Journal, the study reveals that as eggs mature, they deliberately reduce the activity of their waste disposal systems, such as lysosomes, proteasomes, and mitochondria, to keep metabolic activity low and minimize cellular damage.

This discovery was facilitated by analyzing over 100 eggs from healthy donors aged 19–34 at a fertility clinic in Barcelona. The eggs, comprising both fertilization-ready and immature oocytes, were examined using fluorescent probes that tracked cellular organelle activity in real-time. Findings showed that all three major waste disposal and energy-producing components demonstrated roughly 50% lower activity in eggs compared to surrounding support cells, with activity diminishing further as maturation progressed.

Interestingly, live imaging uncovered that in the hours before ovulation, eggs actively expel lysosomes into the surrounding fluid, a process akin to spring cleaning, while mitochondria and proteasomes migrate to the cell's outer edge. This indicates a highly regulated, energy-efficient process aimed at maintaining cell quality over long periods.

The implications of these findings are significant for fertility treatments. Typically, eggs used in in-vitro fertilization are artificially ripened, but such in-vitro matured oocytes often show abnormal behaviors and poorer success rates. In contrast, insights suggest that maintaining a natural, low-metabolism state in eggs could help improve their quality and the likelihood of successful fertilization.

This pioneering study provides the largest dataset of healthy human eggs analyzed directly from women, offering new avenues for enhancing fertility therapies. Future research aims to explore how aging and reproductive diseases may impact these cellular maintenance processes, potentially leading to targeted strategies to boost reproductive success.

Source: https://medicalxpress.com/news/2025-07-discovery-power-cellular-housekeeping-human.html