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Qualitative and quantitative structural changes during pig oocyte maturation
Abstract:
Pig oocytes were examined at hourly intervals after stimulation with hCG. Meiosis was resumed between 20 and 30 h after hCG. This coincided with a decline in the number of mitochondria and evidence is presented which indicates that this was due to fusion. The number of lipid droplets increased and the volume fraction of large vesicles decreased. Both these organelles maintained a close spatial relationship with the endoplasmic reticulum (ER). Mitochondria were clustered at the periphery of the cell before hCG injection but dispersed with maturation. The volume occupied by large vesicles, 'protein bodies' and Golgi also decreased at the edge of the oocyte with the progression of maturation.
Insights
Hormone stimulation triggers pig oocyte maturation, marked by mitochondrial fusion and organelle redistribution. This process is crucial for developmental competence in porcine oocytes.
Area of Science:
- Reproductive Biology
- Cell Biology
- Developmental Biology
Background:
- Oocyte maturation is a complex process involving significant cellular reorganization.
- Understanding organelle dynamics during maturation is key to improving assisted reproductive technologies.
Purpose of the Study:
- To investigate the temporal changes in organelle distribution and morphology in pig oocytes following human chorionic gonadotropin (hCG) stimulation.
- To elucidate the role of mitochondrial dynamics and interactions with the endoplasmic reticulum (ER) during oocyte maturation.
Main Methods:
- Pig oocytes were collected and stimulated with hCG.
- Oocytes were analyzed at hourly intervals to track morphological and organelle changes.
- Mitochondrial distribution, lipid droplet formation, and vesicle volume were quantified.
Main Results:
- Meiosis resumption occurred 20–30 hours post-hCG, coinciding with decreased mitochondrial numbers, likely due to fusion.
- An increase in lipid droplets and a decrease in the volume fraction of large vesicles were observed.
- Mitochondria dispersed from the periphery, and large vesicles, protein bodies, and Golgi decreased at the oocyte edge during maturation.
Conclusions:
- Hormonal stimulation induces significant organelle remodeling in pig oocytes.
- Mitochondrial fusion and redistribution, along with changes in lipid droplets and vesicles, are integral to porcine oocyte maturation.