Impact of vitrification on granulosa cell survival and gene expression

Cryopreservation of ovarian tissue is an essential step in Ovarian Tissue Banking. In order to prevent the formation of ice crystals, typically the tissue is slowly frozen using a cryoprotectant. As an alternative the method of ultra-fast freezing by vitrification becomes more attention for freezing ovarian tissue because it has successfully been used for oocytes, embryos and sperm. However the impact of vitrification on granulosa cells, which are an essential part of ovarian tissue is uncertain. In this study, we have therefore analysed the influence of vitrification on the survival rates of granulosa cells, the impact of DMSO or ethylenglycol containing vitrification protocols and investigated to what extent the gene expression of apoptosis- and temperature-sensitive genes changes. We used the human granulosa cell line KGN as a model for human granulosa cells and determined the survival rate and cell cycle stages by FACS analyses. The change in gene expression was determined by quantitative PCR analyses. Our results show that vitrification is possible in granulosa cells but it reduces cell viability and leads to fluctuations in the cell cycle. The DMSO containing protocol results in a lower amount of dead cells than the ethylenglycol containing protocol. Gene expression analysis reveals that TNF-alpha expression is strongly increased after vitrification, while other apoptosis or temperature-related genes seem to stay unaffected. We conclude that vitrification influences the viability of human granulosa cells. Furthermore, our results suggest that this could be mediated by a change in TNF-alpha gene expression. Vitrification of human granulosa cells reduces cell viability and increases TNF-alpha gene expression.