Comparison of two closed carriers for vitrification of human blastocysts in a donor program

Oocyte and embryo cryopreservation in assisted reproductive technology: past achievements and current challenges

Cryopreservation has revolutionized the treatment of infertility and fertility preservation. This review summarizes the milestones that paved the way to the current routinary clinical implementation of this game-changing practice in assisted reproductive technology. Still, evidence to support "the best practice" in cryopreservation is controversial and several protocol adaptations exist that were described and compared here, such as cumulus-intact vs. cumulus-free oocyte cryopreservation, artificial collapse, assisted hatching, closed vs. open carriers, and others. A last matter of concern is whether cryostorage duration may impact oocyte/embryo competence, but the current body of evidence in this regard is reassuring. From social and clinical perspectives, oocyte and embryo cryopreservation has evolved from an afterthought when assisted reproduction was intended for immediate pregnancy with supernumerary embryos of secondary interest to its current purpose, which primarily is to preserve fertility long-term and more comprehensively allow for family planning. However, the initial consenting process, which still is geared to short-term fertility care, may no longer be relevant when the individuals that initially preserved the tissues have completed their reproductive journey. A more encompassing counseling model is required to address changing patient values over time.

Comparison of the effect of two commercialized vitrification carriers on pregnancy outcomes in freeze-thaw cycles

OBJECTIVE

This study aimed to compare the effects of two brands of commercial vitrification carriers on pregnancy outcomes in freeze-thaw cycles.

METHODS

We included 4871 patients who underwent a "freeze all" strategy using the commercial carriers J.Y. straw and OYASHIPS straw in the Reproductive Center of the First Hospital of Jilin University. The pregnancy outcomes of cleavage-stage embryos and blastocysts were studied separately. Detailed data and the safety of children born from mothers with the two types of carriers were also compared.

RESULTS

Patients who used J.Y. straw had similar clinical pregnancy and live birth rates with one and two cleavage-stage embryo transplantation to those who used OYASHIPS straw. In patients who had blastocyst transplantation, the clinical pregnancy rate of one blastocyst transplanted in those who used OYASHIPS straw was significantly higher than that in those who used J.Y. straw (57.85% vs 47.09%). Among children born from mothers who used J.Y. straw, the congenital disability rate was significantly higher than that in those with OYASHIPS straw.

CONCLUSION

The OYASHIPS straw carrier is cheap and can achieve clinical pregnancy and live birth outcomes comparable to those of J.Y. straw. Therefore, OYASHIPS straw is a good alternative option.

Development of Optimized Vitrification Procedures Using Closed Carrier System to Improve the Survival and Developmental Competence of Vitrified Mouse Oocytes

The open carrier system (OC) is used for vitrification due to its high efficiency in preserving female fertility, but concerns remain that it bears possible risks of cross-contamination. Closed carrier systems (CC) could be an alternative to the OC to increase safety. However, the viability and developmental competence of vitrified/warmed (VW) oocytes using the CC were significantly lower than with OC. We aimed to improve the efficiency of the CC. Metaphase II oocytes were collected from mice after superovulation and subjected to in vitro fertilization after vitrification/warming. Increasing the cooling/warming rate and exposure time to cryoprotectants as key parameters for the CC effectively improved the survival rate and developmental competence of VW oocytes. When all the conditions that improved the outcomes were applied to the conventional CC, hereafter named the modified vitrification/warming procedure using CC (mVW-CC), the viability and developmental competence of VW oocytes were significantly improved as compared to those of VW oocytes in the CC. Furthermore, mVW-CC increased the spindle normality of VW oocytes, as well as the cell number of blastocysts developed from VW oocytes. Collectively, our mVW-CC optimized for mouse oocytes can be utilized for humans without concerns regarding possible cross-contamination during vitrification in the future.