Survival of porcine delipated oocytes and embryos after cryopreservation by freezing or vitrification.

摘要

In the first of 2 studies,the development of delipated porcine oocytes and embryos after cryopreservation by conventional slow cooling or vitrification was examined. Most (93%) of the 27 delipated morulae developed to blastocysts after freezing with1.5 M propanediol + 0.1 M sucrose. Late morulae and early blastocysts delipated at the 2- to 4-cell stage and cultured in vitro survived freezing either with 1.5 M glycerol + 0.25 M sucrose (10 of 18, 56%) or 1.8 M ethylene glycol + 0.25 M sucrose (14 of 19, 74%). Delipated 2- to 4-cell embryos and oocytes could be cryopreserved by vitrification with 40% ethylene glycol, 1 M sucrose and 20% fetal calf serum. Half (7 of 14) of the vitrified, delipated embryos developed to blastocysts after thawing. Of 48 delipated oocytes, 27 (56%) maintained an intact outline of the ooplasm after vitrification and underwent subzonal sperm injection. Fertilization was confirmed in 12 (25%) of the oocytes and 3 (6%) developed to the morula stage. The 2nd study aimed atdeveloping a non-invasive method for cryopreserving porcine embryos after reducing their cytoplasmic lipid content without micromanipulation. Morulae and early blastocysts were centrifuged in the presence of cytochalasin B and cryoprotectants and then frozen immediately. More than half (14 of 24, 58%) of the centrifuged morulae developed to blastocysts after freezing with 1.5 M propanediol + 0.1 M sucrose. Most centrifuged early blastocysts survived freezing with 1.5 M propanediol (30 of 31, 97%), 1.5 Mglycerol (22 of 29, 76%) or 1.8 M ethylene glycol (21 of 29, 72%). The results showed that delipation (lipid removal) from porcine oocytes and embryos at various stages enabled their cryopreservation.