Potential Importance of Vitrification in Reproductive Medicine

Abstract

As early as 1985, ice-free cryopreservation of mouse embryos at -196 degrees C by vitrification was reported in an attempted alternative approach to cryostorage. Since then, vitrification techniques have entered more and more the mainstream of animal reproduction as an alternative cryopreservation method to traditional slow-cooling/rapid-thaw protocols. In addition, the last few years have seen a significant resurgence of interest in the potential benefits of vitrification protocols and techniques in human-assisted reproductive technologies. The radical strategy of vitrification results in the total elimination of ice crystal formation, both within the cells being vitrified (intracellular) and in the surrounding solution (extracellular). The protocols for vitrification are very simple. They allow cells and tissue to be placed directly into the cryoprotectant and then plunged directly into liquid nitrogen. To date, however, vitrification as a cryopreservation method has had very little practical impact on human-assisted reproduction, and human preimplantation embryo vitrification is still considered to be largely experimental. Besides the inconsistent survival rates that have been reported, another problem is the wide variety of different carriers and vessels that have been used for vitrification. Second, many different vitrification solutions have been formulated, which has not helped to focus efforts on perfecting a single approach. On the other hand, the reports of successfully completed pregnancies following vitrification at all preimplantation stages is encouraging for further research and clinical implementation. Clearly, however, attention needs to be paid to the inconsistent survival rates following vitrification.

Improved development by Taxol pretreatment after vitrification of in vitro matured porcine oocytes

“…Recently, vitrification has been widely used to cryopreserve oocytes in many mammals (Kono et al 1991, Arav & Zeron 1997, Isachenko et al 1998, including man (Kuleshova et al 1999, Yoon et al 2000. As vitrification does not require a programmed freezer and the technique itself is easy, safe and highly efficient, it will become an indispensable method in cryobiology in the future (Kuleshova & Lopata 2002, Liebermann et al 2002. Normal offspring have been produced from the vitrified mature (Kono et al 1991, Hamano et al 1992, Kuleshova et al 1999, Yoon et al 2000 and immature oocytes (Vieira et al 2002).…”

Slow freezing should not be totally substituted by vitrification when applied to day 3 embryo cryopreservation: an analysis of 5613 frozen cycles

“…The authors concluded that the number of single-embryo transfers with vitrified embryos was limited, and the results did not prove that vitrified embryos were more viable than slow frozen embryos. In the current study, we found that slow [9] and may have higher potential cell toxicity, which may be one of the major factors affecting development of embryos. Several studies have shown similar pregnancy and implantation rates between slow freezing and vitrification [13,27].…”

“…Vitrification obtains a higher embryo survival rate and fully intact blastomere rate compared with slow freezing [8]. However, vitrification uses high concentration of cryoprotectants [9] and there are still concerns regarding its safety. The effect of vitrification on embryo development potential and birth outcomes after vitrification still needs to be determined.…”

Cryopreservation of Sheep Produced Embryos – Current and Future Perspectives

“…In fact, vitrification is based on embryo manipula-tion into different carrier tools applied to minimize the volume and to submerge the sample quickly into liquid nitrogen, allowing an ultrafast freezing speed, which avoids ice crystal formation, thus eliminating its deleterious effects in the cell [157]. This technique combines the use of small volumes with high concentration of two or more cryoprotectants [158] and it can be more adapted to IVP embryos [149,159,160].…”