Cryopreservation of Oocytes and Embryos in in Vitro Fertilization and Embryo Transfer

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This study revealed that 3-step addition of dimethylsulfoxide, DMSO, and sucrose to murine embryos over no more than 15 minutes, together with final equilibration at room temperature for within a 10-minute period, allowed more than 95 per cent of thawed embryos to develop into expanded blastocyts in vitro. Temperature holding for 30 minutes after seeding also improved post-thaw viability of embryos significantly as compared with holding for 0 to 60 minutes. In addition to those time factors, sucrose in both freezing and thawing steps contributed significantly to the high viability, whereas sucrose in either freezing or thawing steps alone did not. Being based upon these basic knowledges, cryopreservation of human embryos was performed in in vitro fertilization program according to the Ethical Statements on Human Embryo Cryopreservation issued by the Japan Society of Obstetrics and Gynecology. Fifty-two human embryos were tehn cryopreseved with 1.5 M DMSO and 0.1 M sucrose as cryoprotec … More tants. 42 frozen embryos were thawed and transferred in 7 spontaneous cycles after morphological evaluation of embryonal integration and viability. As a result, 4 pregnancies have been established, and one of them led to a successful delivery of twin female babies at 37th week of gestation on December the 25th in 1989, which was the first case of successful delivery of frozen-thawed human embryos in Japan. The latter part of this study consisted of oocyte cryopreservation using murine superovulated oocytes. Ultrastructural investigation of the intracellular organellas including mitochondira of post-thaw oocytes revealed a various degrees of structural changes which strongly suggested latent decrease in cellular viability. Chromosomal damages could also be suggested since mature oocytes was at the stage of meiosis arrest in the metaphase II. As a conclusion, this study revealed the necessity of further investigation and development of freeze/thaw protocols in terms of the optimal breakpoint temperature, choice of cryoprotectants, and seeding procedures. Less