Comparison of The Effects of Vitrification on Gene Expression of Mature Mouse Oocytes Using Cryotop and Open Pulled Straw

Objective Oocyte cryopreservation is an essential part of assisted reproductive technology (ART) which was recently introduced into clinical practice. This study aimed to evaluate the effects of two vitrification systems (Cryotop and Open Pulled Straw, OPS) on mature oocytes gene expressions. MaterialsAndMethods The survival rate of metaphase II (MII) mouse oocytes were assessed after cryopreservation by vitrification in: (i) OPS; or (ii) Cryotops and then compared the fertilization rate of oocytes in these two methods. In the second experiment, we determined the effects of two vitrification methods on the expression of HSPA1A, MnSOD and ß-actin genes in vitrified-warmed oocytes. Denuded MII oocytes were vitrified in two concentrations of Vitrification Solution (VS1 and VS2) by Cryotop and straw and compared with fresh control oocytes. Results MnSOD expression increased in the vitrified-warmed group both in OPS and Cryotop compared with the controls. We only detected HSPA1A in VS1 and control groups using Cryotop. The survival rate of the oocytes was VS1: 91.2% and VS2: 89.2% in the Cryotop groups (p=0.902) and VS1:85.5% and VS2: 83.6% in the OPS groups (p=0.905). There were no significant differences between the Cryotops and OPS groups (p= 0.927) The survival rate in the Cryotop or OPS groups was, nevertheless, significantly lower than those recorded for the control group (p≤ 0.001). The fertilization rates of the oocytes were VS1: 39% and VS2: 34% in the Cryotop groups (p=0.902) and VS1:29% and VS2: 19.7% in the OPS groups (p=0.413). The fertilization rates were achieved without significant differences among the Cryotop and OPS groups (p=0.755). Conclusion Our results indicated that Cryotop vitrification increases both cooling and warming rate, but both Cryotop and OPS techniques have the same effect on the mouse oocytes after vitrification.