Epigenetic Changes in Equine Embryos after Short-Term Storage at Different Temperatures

Area of Science:

• Reproductive Biology
• Epigenetics
• Embryology

Background:

• Assisted reproductive techniques can induce epigenetic modifications affecting embryonic development.
• Short-term storage temperature of fresh equine embryos is a critical factor before transfer.

Purpose of the Study:

• To investigate the effects of two storage temperatures (5°C and 20°C) on equine embryo morphology, gene expression, and DNA methylation.
• To assess the impact of short-term storage on equine embryos collected on days 7 and 8 post-ovulation.

Main Methods:

• Equine embryos (n=80) were collected and stored for 24 hours at either 5°C or 20°C.
• Analysis included embryo morphology, mRNA expression of key developmental genes, and gene-specific/global DNA methylation (5mC, 5hmC).
• Storage medium parameters (pH, MDA) were also evaluated.

Main Results:

• Embryo size differed significantly between storage groups (larger at 5°C, smaller at 20°C).
• mRNA expression of genes related to growth, pregnancy recognition, DNA methylation, and apoptosis was altered by storage.
• Gene-specific DNA methylation (ESR1, NANOG, DNMT1) was reduced in embryos stored at 20°C compared to controls.

Conclusions:

• Short-term storage of equine embryos, regardless of temperature, modifies gene expression and DNA methylation patterns.
• While 20°C storage showed some advantages over 5°C, both conditions may compromise embryo viability and post-transfer development.
• This study provides novel insights into the DNA methylation status of fresh equine embryos at critical developmental stages.