Open Versus Closed Vitrification of Mouse Oocytes Using the Same Carrier

Abstract

Oocyte cryopreservation is considered a growing service in the field of Assisted Reproductive Technology (ART), which is achieved through a cryopreservation technique called vitrification. This technique allows for an ultra-rapid cooling rate for oocytes, followed by loading them onto a carrier device and preserving them for an extended period in liquid nitrogen. Vitrification can be performed using two protocols: the closed system and open system. Numerous studies have examined the differences between the two systems, but we were unable to find one specifically targeted at comparing the implementation of the same carrier for both systems. The Rapid-iTM device is designed as a closes system, and we hypothesized that it could yield similar results when used as an open vitrification device as well. In this thesis, we aim to study this proposition by performing both techniques and analyzing our findings. To examine this hypothesis, we utilized 173 mice oocytes for this project. These oocytes are then dividing into four groups based on maturation stage and the vitrification system used. The survivability of the oocytes post-thawing was determined based on their physical appearance under an inverted microscope. Our data showed no significant difference in the survival rate, with 95% for the closed system and 93% for the open system. This confirms our hypothesis that the Rapid-iTM device can be successfully used for both protocols. Furthermore, our data also revealed no correlation between the maturation stage and survival rate, proving that the same device can be utilized regardless of the maturation stage. However, further studies are needed to evaluate in vitro maturation (IVM), fertilization rate, and embryo development rate. These findings have significant implications for clinical applications, such as reducing the training time for embryologists to perform both protocols using different carriers. Standardizing the procedure and using one set of devices can also help reduce operational costs and logistical difficulties compared to employing multiple devices.