Vitrification of mouse and human blastocysts using a novel cryoloop container-less technique

Objective: To vitrify mouse and human blastocysts with use of the cryoloop procedure and to assess subsequent development. Design: Controlled study of vitrification of mouse and human blastocysts. Setting: Research department of a private assisted reproductive technology unit. Patient(s): Blastocysts that were not suitable to be frozen were donated from patients. Intervention(s): Culture of pronucleate embryos in sequential media to the blastocyst stage. Main Outcome Measure(s): Survival of the vitrification procedure was assessed by reexpansion, hatching, and outgrowth in culture. In addition, the viability of mouse blastocysts was assessed after transfer to pseudopregnant recipients. Result(s): Vitrification of mouse blastocysts did not affect the ability to reexpand, hatch, or outgrow in culture. Furthermore, implantation rates and fetal development were equivalent for nonfrozen and vitrified blastocysts. Vitrified human blastocysts were able to hatch and outgrow in culture at rates similar to nonfrozen controls. Conclusion(s): Cryoloop vitrification was able to cryopreserve mouse and human blastocysts without any reduction in the ability to reexpand and hatch in culture. Furthermore, viability was not reduced by the cryoloop vitrification of mouse blastocysts. (C) 1999 by American Society for Reproductive Medicine.