Abstract:

Objective To investigate the effects of vitrification and programmed cryopreservation on human ovarian cortex. Methods Ovarian tissue samples were collected from patients with ovarian disease and were randomly divided into vitrification freezing group，programmed freezing group and control group. We carried out histological analysis of ovarian tissue，isolation and counting of preantral follicles，and in vitro culture of ovarian cortex. The follicle morphology of ovarian tissue，the number of follicles in suspension of ovarian tissue and the estradiol level in the supernatant of ovarian cortical culture were compared among the three groups. Results （1）The intact rate of primordial follicles in the ovarian cortex of the two freezing groups was significantly lower than that of the control group（84.62% & 80.21% vs. 97.93%，P < 0.001），but there was no statistical significance between the two freezing groups（P > 0.05）. Normal rate of secondary follicles in programmed freezing group was significantly lower than that in the control group（37.5% vs. 88.24%，P < 0.05）.（2）The number of primary follicles in suspension of ovarian tissue per unit volume in two freezing groups was significantly lower than that in the control group［（76.50 ± 8.91）&（79.67 ± 10.40）vs.（91.50 ± 8.70），P = 0.001］. There were significant differences in the number of primary follicles and secondary follicles in the 100 microliters in suspension of ovarian tissue between programmed freezing group and the control group［（22.83 ± 3.74）&（9.50 ± 3.46）vs.（27.33 ± 3.02）& （12.55 ± 3.25），P < 0.05］.（3）At the initial stage of in vitro culture（D2⁃D6），the level of E2 secreted by freeze⁃ thawing tissue was lower than that of fresh tissue（P < 0.05），and there was no statistical significance in the E2 level of supernatant among each group（P > 0.05）. Conclusion Both vitrification and programmed freezing can effectively preserve the activity of ovarian tissue. The vitrification method is more effective in preserving secondary follicles than the programmed method，and it is simple and easy to operate，which is more suitable for cryopreservation of ovarian tissue. 

Key words:

vitrification, programmed cryopreservation, ovarian cortex, follicle activity