Vitrification of human and mouse embryos using the Rapid-i™

Abstract

OBJECTIVE: Vitrification normally uses direct contact with liquid nitrogen to facilitate the glass-like state. Concerns have been raised with regards to the safety and sterility of this procedure. The Rapid-i™ is a unique device that uses super-cooled air to vitrify the sample. Following development and optimization using mouse oocytes/embryos the Rapid-i™ has been used to vitrify day 3 human embryos. DESIGN: Experimental design and clinical evaluation. MATERIALS AND METHODS: Mouse oocytes, pronuclear oocytes, 8 cell embryos and blastocysts (n = >50 for each group) were vitrified using the Rapid-i™. Oocytes/embryos were warmed immediately and subsequent survival, embryo development and blastocyst cell number were recorded and compared to sibling non-vitrified controls. Embryo transfers were performed to determine viability following vitrification. For clinical evaluation day 3 human embryos from 34 patients were vitrified/warmed as described above and subsequently transferred. Statistical analysis: Fisher's exact test. RESULTS: Survival rates for mouse oocytes/embryos was >95%. Subsequent blastocyst development (Day 5) was >80%, which did not differ significantly from non-vitrified control embryos. The mean cell number in the resulting blastocysts of vitrified embryos was also not significantly different from the control. Embryo transfer of mouse blastocysts generated from vitrified pronuclear oocytes resulted in fetuses with developmental parameters comparable to control embryos. Of the 99 warmed human embryos 87% survived. A mean of 2.1 embryos were transferred resulting in a clinical pregnancy rate of 41%. CONCLUSION: The Rapid-i™, which has no direct liquid nitrogen contact during vitrification or storage, is successful at vitrifying mouse oocytes/embryos. The Rapid-i™ is capable of vitrifying day 3 human embryos with survival and pregnancy rates comparable to the open system (cryoloop) normally used.