Ultrastructure and mitochondrial numbers in pre- and postpubertal pig oocytes

Area of Science:

• Reproductive Biology
• Developmental Biology
• Oocyte Biology

Background:

• Prepubertal pig oocytes exhibit reduced developmental competence compared to postpubertal counterparts.
• Oocyte quality is crucial for successful embryonic development and reproductive outcomes.

Purpose of the Study:

• To comprehensively analyze oocyte ultrastructure in prepubertal and postpubertal pigs.
• To quantify mitochondrial numerical density and total number using stereology.
• To correlate oocyte ultrastructure and mitochondrial content with developmental competence.

Main Methods:

• Design-unbiased stereological approach for quantifying organelles.
• Transmission electron microscopy for ultrastructural analysis.
• Comparison of oocytes from prepubertal and postpubertal pigs of varying diameters.

Main Results:

• Smaller prepubertal oocytes showed active ultrastructure with cumulus cell contact but had fewer total mitochondria.
• Mitochondrial densities did not differ significantly between groups.
• Mature postpubertal oocytes displayed specific characteristics like metaphase II, lack of cumulus contact, and central mitochondria.
• Large oocytes (pre- and postpubertal) had ultrastructure compatible with higher developmental competence.

Conclusions:

• Oocyte size and mitochondrial content are associated with developmental competence in pigs.
• Reduced total mitochondria in smaller prepubertal oocytes may explain their lower developmental capacity.
• The increased mitochondrial pool in larger oocytes supports early embryonic development.