Steroids and miRNAs in assessment of ovarian tissue damage following cryopreservation

Ovarian cortical tissue cryopreservation is a relatively novel approach to preserving fertility in women diagnosed with cancer. However, the effects of freezing-thawing are not fully understood, mainly due to the lack of suitable methods to assess tissue's survival after thawing. Disparities in steroid production have been associated with ovarian failure by disrupting folliculogenesis, ovulation and oocyte apoptosis. Moreover, specific miRNAs, identified in human ovarian follicles, are thought to play a fundamental role in folliculogenesis. In this study, we investigated the possible interplay between the ovarian steroidal production and miRNA expression patterns in spent culture media, as potential non-invasive markers for ovarian tissue damage after cryopreservation. Cryopreservation of ovarian cortical tissue decreased (P < 0.05) both steroid production (oestradiol and progesterone) and expression of miRNA-193b and 320A in spent culture media over 5 days; however, expression of miRNA-24 increased (P < 0.05). The number of primordial follicles was also reduced (P < 0.05) in fresh-cultured and cryopreserved-cultured cortical tissues when compared with fresh tissues. Downregulation of miRNA-193b and miRNA-320A together with upregulation of miRNA-24 could have a synergistic role in cell apoptosis, and consequently leading to reduced oestradiol and progesterone production. Thus, there appears to be an interplay between these miRNAs, ovarian steroid production and cell damage, which can be further explored as novel non-invasive markers of cell damage following cryopreservation.