The human oocyte: Vitrification Vitrification

The past 50 years have yielded impressive breakthroughs in cryopreservation as applied to the discipline of reproductive biology. Techniques were usually derived in experimental and domestic animals and subsequently applied to humans. The first success in freezing cells was achieved in spermatozoa (1), followed by successful cryopreservation of preimplantation embryos at different stages of development (2–4). Since the first report in 1972 of the cryopreservation of mammalian embryos resulting in the birth of live mice offspring (2), attempts to cryopreserve human oocytes, similar to the results with oocytes of domestic animals, mostly failed for many years. However, the development of an ultra-rapid vitrification method now means that oocytes can be cryopreserved without loss of their viability, and such oocytes may be used clinically (5).