Effect of maternal aging and vitrification on mitochondrial DNA copy number in embryos and spent culture medium

Area of Science:

• Reproductive Biology
• Mitochondrial Genetics
• Embryology

Background:

• Maternal aging is known to affect oocyte and embryo quality.
• Mitochondrial DNA (mtDNA) quantity and quality are crucial for embryonic development.
• Vitrification is a common cryopreservation technique for embryos.

Purpose of the Study:

• To investigate the impact of maternal aging on mitochondrial DNA (mtDNA) copy number in bovine embryos.
• To assess the effect of maternal aging on cell-free mtDNA (cf-mtDNA) released into spent culture medium (SCM).
• To examine the influence of vitrification on mtDNA copy number and cf-mtDNA in embryos from young and aged cows.

Main Methods:

• Oocytes were collected from young (20-40 months) and aged (>140 months) cows.
• Early stage embryos were produced, cultured, and assessed for mtDNA copy number and cf-mtDNA in SCM using real-time PCR.
• Experiments included zona pellucida (ZP)-free embryos and vitrified/warmed embryos.

Main Results:

• Embryos from young cows had higher mtDNA copy number than aged cows at 48 hours post-insemination.
• No significant difference in cf-mtDNA was observed in SCM initially, but ZP-free embryos from aged cows showed higher cf-mtDNA.
• Vitrification led to lower mtDNA copy number in young cow embryos and higher cf-mtDNA in aged cow embryo SCM.

Conclusions:

• Maternal aging significantly affects mitochondrial kinetics and mtDNA copy number in bovine embryos.
• Vitrification interacts with maternal age to alter mtDNA content and release in embryos.
• These findings have implications for understanding reproductive aging and assisted reproductive technologies.