Vitrification of bovine germinal vesicle oocytes significantly decreased the methylation level of their in vitro 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 2 μM 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 2 μM 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. 5-MeC and SC-WGBS were utilised to detect the DNA methylation patterns of vitrified bovine GV oocytes and their in vitro derived MII oocytes. Results showed that the methylation level of the V_GV group was similar to that of the F_GV group, while the methylation level of the V_MII group was significantly lower than that of the F_MII group. Moreover, supplementation of 2 μM Res in IVM medium significantly improved maturation and development ability of vitrified GV oocytes by restoring their DNA methylation levels. [ABSTRACT FROM AUTHOR]