Reproductive aging is associated with changes in oocyte mitochondrial dynamics, function, and mtDNA quantity.

Area of Science:

• Reproductive biology
• Cellular biology
• Aging research

Background:

• Mitochondria play a crucial role in mammalian reproduction.
• Oocyte quality declines with advanced maternal age.
• The specific mitochondrial changes contributing to age-related oocyte quality decline are not fully understood.

Purpose of the Study:

• To investigate the relationship between aging and mitochondrial alterations in mouse oocytes.
• To compare mitochondrial morphology, mitochondrial DNA levels, mitochondrial stress response, and reactive oxygen species in oocytes from young and old mice.

Main Methods:

• Comparative analysis of oocytes from young (9 weeks) and old (12 months) C57BL/6J mice.
• Assessment of mitochondrial morphology and dynamics throughout folliculogenesis.
• Quantification of mitochondrial DNA (mtDNA) levels.
• Measurement of mitochondrial unfolded protein response (mt-UPR) gene expression.
• Evaluation of reactive oxygen species (ROS) levels under baseline and induced oxidative stress conditions.

Main Results:

• Oocytes from old mice exhibited smaller mitochondria with reduced coverage in primary follicles.
• Mature oocytes (Metaphase II) from aged mice had significantly lower mtDNA levels and elevated Hspd1 (mt-UPR) gene expression.
• Aged oocytes showed increased ROS levels following hydrogen peroxide (H2O2) treatment, indicating heightened oxidative stress.

Conclusions:

• Oocyte aging is associated with significant mitochondrial alterations, including changes in morphology and reduced mtDNA.
• Mitochondrial dysfunction and increased oxidative stress contribute to age-related decline in oocyte quality.
• Understanding these mitochondrial mechanisms could lead to diagnostic and therapeutic advancements in reproductive medicine.