Vitrification: the pioneering past to current trends and perspectives of cryopreserving human embryos, gametes and reproductive tissue

Abstract

After more than 2 decades of development in mammalian models and the clinical focus of a few pioneering laboratories, vitrification of human oocytes and embryos has transformed today's assisted reproductive technology (ART) industry. Our ability to cryopreserve gametes and embryos without fear of the damaging effects of ice formation has instilled great confidence in post-warming specimen viability. In turn, clinical treatment options are progressively eliminating fresh embryo transfer (ET; ie, freeze-all cycles), integrating preimplantation genetic screening and contemplating the use of cryopreserved oocytes as a viable resource. Vitrification's impact on clinical treatments is akin to the advent of sperm injection technology in the 1990s on male factor infertility. An appreciable and quantifiable difference was made, with procedural efficacy and global reliability essentially being guaranteed. Yet, there are challenges in the current trends and perspectives in how this technology is and will be optimized in the future. User variation in vitrification products and procedures warrants stricter adherence to quality control measures to enhance specimen biosafety and patient satisfaction, while reducing potential liability concerns. Furthermore, future progress in our understanding of the chemical and cryophysical processes of vitrification will insure the effective cryostorage of reproductive tissues and gametes at a level attained for embryo cryopreservation today.

The Role of Vitrification in Spanish Reproductive Labs: A Cryo-revolution Led by Strategic Freezing

“…Although it took more than 20 years of development, vitrification has transformed the IVF industry. (Schiewe and Anderson 2017) Cryopreservation was important for ARTs from a very early stage (Cohen et al 2005). Alan Trounson's team in Australia pushed it at the beginning: after they announced the first pregnancy achieved from a frozen embryo in 1983 (Trounson and Mohr 1983), in 1984, their successful use of slow freezing techniques led to the birth of the first baby whose conception was assisted through these techniques.…”

A 3-D printed vitrification device integrated with French straws

“…Vitrification of living biological materials was introduced in the late 1900 s and has continued to advance as an emerging cryopreservation approach [1] . Compared with conventional equilibrium cooling with relatively slow rates (e.g., 1–50 °C/min) vitrification uses ultra-rapid cooling (e.g., > 5,000 °C/min) to limit or prevent formation of crystalline ice and produce an amorphous solid (i.e., ‘glass state’) [2] .…”

Vitrification: Fundamental Principles and Its Application for Cryopreservation of Human Reproductive Cells

“…While a device system may be perfected, or not, within a laboratory, when samples are transferred for warming to another laboratory, reduced outcomes may occur. This interlaboratory variation poses potential liability issues to both programs [45,46]. Even when both programs are competent in their procedures, the relationships between cooling and warming thermodynamics as discussed above can have applied consequences.…”

“…The latter event could allow LN 2 seepage to occur and problematic warming events to transpire if not accounted for properly [56]. Variations in device systems that place the end user at risk of unexpected poor outcomes, like non-recovery and high degeneration rates, create serious liability issues to IVF programs, as recently discussed [46]. Liability concerns can also stem from poor manufacturer design or user compliance to quality management practices.…”

“…It should be noted that the determining factor to remove the "experimental" classification was dictated by medical insurance factors to aid the former female population. Although oocyte vitrification has numerous potential clinical benefits, including IVF cycle rescue and elective fertility preservation when a sperm provider fails to produce or is unavailable, respectively, its "nonexperimental" classification has been potentially misleading [46]. Blastocysts derived from vitrified oocytes are comparable to those derived from fresh oocytes, in terms of euploidy and live birth rate potential [68,69]; however, the overall developmental competence of zygotes to the blastocyst stage continues to be delayed and reduced overall [69].…”