Table 1.

Impact of oocyte vitrification on DNA methylation in humans

References	Materials	Number of oocytes and embryos	Technology of assessment	Studied sequences	Conclusions
Liu et al. [109]	Vitrified MII, MII from IVM, GV	56 in vivo MII, 106 MII after MIV, 122 MII from vitrified GV	Immunofluorescence (5mC)	Global analysis	No significant differences in fluorescence intensities between the three oocyte groups
De Munck et al. [110]	MII from donated oocytes, sibling cohort	31 embryos (D3) from 17 fresh MII and 14 vitrified MII	Immunofluorescence (5mC, 5hmC)	Global analysis	No significant differences in fluorescence intensities between embryos from fresh and vitrified oocytes (5mC 1.0 ± 0.49 vs 0.83 ± 0.41; 5hmC 1.0 ± 0.40 vs 0.81 ± 0.36)
Al-Khtib et al. [111]	MII from IVM (GV donated for research)	77 MII after IVM from 184 vitrified VG, and 85 MII from 120 fresh GV	Pyrosequencing	H19 (pool of 3 oocytes) and KCNQ1OT1	Oocyte vitrification at the GV stage does not affect the methylation profiles of H19-DMR et KvDMR1 of the in vitro matured oocytes

D day of embryo culture, GV oocyte at germinal vesicle stage, 5hmC 5-hydroxymethylCytosine, IVM in vitro maturation, 5mC 5-methylCytosine, MII oocyte at metaphase II stage