Oocytes recovered after ovarian tissue slow freezing have impaired H2AX phosphorylation and functional competence

Area of Science:

• Reproductive biology
• Cryobiology
• Molecular biology

Background:

• Oocyte cryopreservation is crucial for fertility preservation.
• Cryopreservation techniques like slow freezing and vitrification can induce DNA damage in oocytes.
• Histone H2AX phosphorylation (γ-H2AX) is a marker of DNA double-strand breaks.

Purpose of the Study:

• To compare the functional competence and DNA damage response (γ-H2AX) of mouse oocytes after slow freezing versus vitrification of ovarian tissue.
• To assess the impact of cryopreservation methods on oocyte maturation and parthenogenetic activation.

Main Methods:

• Mouse model utilized for ovarian tissue cryopreservation.
• Comparison of slow freezing and vitrification techniques.
• Assessment of γ-H2AX foci in germinal vesicle (GV) stage oocytes.
• Evaluation of in vitro maturation (IVM) and parthenogenetic activation rates.

Main Results:

• No significant difference in γ-H2AX foci between slow freezing and vitrification groups at the GV stage.
• Significant delay in germinal vesicle breakdown during IVM for the slow-freezing group, but similar maturation rates.
• Significantly lower parthenogenetic activation rates in the slow-freezing group compared to vitrification and control groups.
• Perturbed H2AX phosphorylation in the slow-freezing group.

Conclusions:

• Slow freezing of ovarian tissue leads to impaired DNA damage sensing and repair in oocytes.
• Reduced functional competence of oocytes after slow freezing may negatively affect reproductive outcomes.
• Vitrification appears to be a superior cryopreservation method for maintaining oocyte quality and function.