Vitrification of bovine germinal vesicle oocytes significantly decreased the methylation level of their derived MII oocytes.

Context: The vitrification of oocytes is important for the conservation of animals, and the effect of vitrification on methylation patterns of bovine oocytes remains unclear.

Aims: This article aims to investigate the effect of vitrification on the DNA methylation patterns on vitrified GV oocytes and their in vitro derived MII oocytes.

Methods: 5-MeC staining and single-cell whole genome bisulphite sequencing (SC-WGBS) were utilised to analyse fresh GV oocytes (F_GV group), MII oocytes (F_MII group), vitrified GV oocytes (V_GV group) and their in vitro derived MII oocytes (V_MII group).

Key Results: Results of both 5-MeC staining and SC-WGBS showed that no significant difference was found between the F_GV group and the V_GV group, while the methylation level of the V_MII group was significantly lower than that of the F_MII group. Moreover, supplementation of 2μM resveratrol (Res) in IVM medium significantly improved maturation and development ability of vitrified GV oocytes by restoring their DNA methylation levels.

Conclusion: In conclusion, vitrification of bovine GV oocytes significantly decreased the DNA methylation level of their in vitro derived MII oocytes, and 2μM Res improved their development ability by restoring DNA methylation level.

Implications: Our results provide an efficient approach to improve the maturation and fertilisation ability of vitrified GV oocytes.