The effect of flash-freezing temperature on stallion sperm DNA structure

Area of Science:

• Reproductive Biology
• Animal Science
• Genetics

Background:

• Sperm DNA integrity is crucial for fertility and is often preserved through flash-freezing.
• The impact of different flash-freezing storage temperatures on stallion sperm DNA structure is not well understood.
• Variability in DNA assay results may be influenced by cryopreservation methods.

Purpose of the Study:

• To evaluate the effect of flash-freezing storage temperature on stallion sperm DNA structure using the neutral comet assay.
• To determine intra- and inter-assay and intra- and inter-stallion variabilities associated with the neutral comet assay.
• To investigate correlations between comet assay measures, Sperm Chromatin Structure Assay (SCSA) variables, and sperm morphology.

Main Methods:

• The neutral comet assay was employed to assess DNA structure in fresh and flash-frozen stallion sperm.
• Sperm were flash-frozen at three different temperatures: -60°C (freezer), -78.5°C (dry ice), and -196°C (liquid nitrogen).
• Variability was assessed across assays and stallions, and correlations with SCSA and morphology were analyzed.

Main Results:

• All flash-freezing methods resulted in significantly higher comet tail measures compared to fresh sperm DNA (P < 0.05).
• No significant differences in DNA structure were found among the different flash-freezing temperatures (P > 0.05).
• Comet tail measures showed negative correlations with morphologically normal sperm and positive correlations with abnormal sperm features.

Conclusions:

• Flash-freezing significantly alters stallion sperm DNA structure, irrespective of the storage temperature used.
• Intra- and inter-stallion variability was lower for comet head measures than for tail measures.
• The observed DNA structural changes in flash-frozen sperm do not necessarily imply a reduction in fertility.