Highly efficient vitrification for cryopreservation of human oocytes and embryos: the Cryotop method

Vitrification is frequently referred to as a novel technology of cryopreservation in embryology, although some young embryologists were born after its first successful application. Unfortunately, in spite of the accumulated evidence regarding its enormous potential value, most domestic animal and human laboratories use exclusively the traditional slow-rate freezing with its compromised efficiency and inconsistency. The purpose of this paper is to clarify terms and conditions, to summarize arguments supporting or disapproving the use of vitrification, and to outline its role among assisted reproductive technologies. To provide evidence for the potential significance of vitrification, achievements with the Cryotop technology, an advanced version of the "minimal volume approaches" is analyzed. This technology alone has resulted in more healthy babies after cryopreservation of blastocysts than any other vitrification technique, and more successful human oocyte vitrification resulting in normal births than any other cryopreservation method. The value of this method is also demonstrated by achievements in the field of domestic animal embryology. A modification of the technique using a hermetically sealed container for storage may help to eliminate potential dangers of disease transmission and open the way for widespread application for cryopreservation at all phases of oocyte and preimplantation embryo development in mammals.