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 fr om patients. Intervention(s): Culture of pronucleate embryos in sequential media to the blastocyst stage. Main Outcome Measure(s): Survival of the vitrification procedure was assess ed by reexpansion, hatching, and outgrowth in culture. In addition, the via bility of mouse blastocysts was assessed after transfer to pseudopregnant r ecipients. Result(s): Vitrification of mouse blastocysts did not affect the ability to reexpand, hatch, or outgrow in culture. Furthermore, implantation rates an d 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 hu man blastocysts without any reduction in the ability to reexpand and hatch in culture. Furthermore, viability was not reduced by the cryoloop vitrific ation of mouse blastocysts. (C) 1999 by American Society for Reproductive M edicine.