Maximizing the efficacy of commercial vitrification and warming for human blastocysts by cryoprotectant management: challenging validation results of a one-step model

• Published in: Reproductive biomedicine online 2024-05, Vol.48, p.104017, Article 104017
• Main Authors: Gunst, J., Hostens, K., Standaert, V., Roggeman, S., Vijver, A. Van De
• Format: Article
• Language: English
• ISSN: 1472-6483
• DOI: 10.1016/j.rbmo.2024.104017

In recent decades, vitrification and warming of human oocytes and embryos involved a labour-intensive, multi-step process. Emerging data on human blastocysts indicate that one-step warming, employing various sucrose concentrations following multi-step vitrification yields comparable survival rates, developmental potential and similar ongoing pregnancy rates. This study aims to optimize human blastocyst cryopreservation by exploring a total one-step approach, assessing osmotic responsiveness through survival, re-expansion, and 24-hour developmental competence. Research consented vitrified blastocysts, using Rapid-i and ethylene glycol / 1,2-propanediol standard vitrification procedures, were used in this validation. All warming steps were performed at 37°C. In a first series, 90 blastocysts were randomly allocated to 6 different groups (15 per group) and warmed in a single step using 1, 0.5 or 0.25 M sucrose. In a second series, surviving blastocysts underwent ethylene glycol / 1,2-propanediol /sucrose single step vitrification at either 37°C or room temperature (RT) again followed by single step warming using the same sucrose concentration. Considering the results from the first series, additional embryos were included and only treated at 37°C. Combined results of both series are summarized in the table. Overall, >95 % of blastocysts were considered transferable following single step warming (138/145). The first series indicated better results when single-step vitrification was performed at 37°C and more embryos were added to these subgroups in series 2. Following single-step vitrification and warming at 37°C, re-expansion potential favoured 1M sucrose 47/49 (96%) versus 0.5M 20/25 (80%) (P=0.03) and 0.25M 18/24 (75%) (P=0.01). No statistical difference in developmental competence was observed. Compared to validation data after standard multi-step vitrification and warming, single-step vitrification combined with single-step warming in 1M sucrose are comparable in terms of survival and re-expansion, but seem to be better in developmental competence. First series confirms the increasing evidence that single-step blastocyst warming after standard vitrification gives highly efficient results. Furthermore, our findings suggest that a 1-step approach for vitrification can work. This has the potential to further optimize cryopreservation techniques, mitigating potential cytotoxicity through minimal cryoprotectant exposure during vitrification and warming of blas