O-41: Comparison of Vitrification Systems inHuman Oocytes and Evaluation of HSP A1Aand MnSOD Gene Expression Patterns

Background: The aim of this study was to compare two vitrification systems (Cryotop and OPS) on mouse MII oocytes and evaluate its effects on expression of heat shock protein A1A and MnSOD genes. Materials and Methods: Groups of about 15 oocytes without cumulus complexes (granulose, et. al.) were collected and exposed to equilibration and vitrification solutions before loading the oocytes into open pulled straws (OPS method) or Cryotop, and carriers transferred to liquid nitrogen. For thawing the oocytes are exposed to three solutions of gradually declining concentrations of sucrose. After thawing live oocyes were subjected to IVF and cultured in vitro to develop into pronuclear stage. Survival of vitrified-warmed oocytes and rate of fertilization were evaluated; gene expression (HSP A1A, MnSOD and ß-actin) of vitrified-warmed oocytes were also examined by reverse transcriptase polymerase chain reaction (RT-PCR).Results: Survival rates of each group were separately compared to control and the results showed that there were significant differences between each experimental group as compared to control (p ≤ 0.05) reduced in vitrified- warmed (Cryotop: 39 %, 34 %, OPS: 29.2 %, 19.7 %) oocytes compared to control (88.36). The expression of MnSOD increased in vitrified-warmed samples as compared to control oocytes. We also detected HSP A1A only in the control (EG + DMSO) group using either Cryoptop or OPS. Conclusion: Vitrification of oocytes by cryotop resulted in higher survival rate, lower developmental competence, and lower fertilization rate of vitrified-warmed oocytes may be because of changing expression rates of important genes after thawing. Further genetic screens can be done to determine expression patterns involved in this effect.