Birth of piglets from frozen embryos

Cryopreservation of Porcine Gametes, Embryos and Genital Tissues: State of the Art

“…However, pig oocytes, zygotes and cleavage embryos are rich in cytoplasmic lipids, and very sensitive to temperatures below 15ºC (Wilmut 1972), a sensitivity that decreases -along with the amount of lipids-with development, towards peri-hatching blastocysts (Niimura and Ishida 1980). Offspring has been obtained after embryo transfer (ET) of slow-frozen and thawed 2-4 cell pig embryos where these cytoplasmic lipids were removed in vitro (de-lipation) before cooling (Hayashi et al 1989, Nagashima et al 1994, 1995, 1996 and thereafter the technique, albeit cumbersome, has been thoroughly applied (Yoneda et al 2004). The results enhanced when the cytoskeleton was preserved from damage using exogenous chemicals (Shi et al 2006).…”

Factors Affecting Cryopreservation of Porcine Oocytes

“…Nevertheless, since survival and development of vitrified porcine zygotes (having the same size and lipid content as oocytes) is significantly higher than those of vitrified mature or immature oocytes [11,12], ultra-structural characteristics specific to those unfertilized oocytes should also be considered as potential reasons for their low cryotolerance. In pigs, traditional freezing could be successfully applied for semen [5] and even for in vivo produced embryos [13][14][15]; however it does not seem to work well for oocytes [16]. The first success in cryopreservation of porcine oocytes (i.e.…”

Improved Survival of Porcine Hatched Blastocysts Cryopreserved with Glycerol and Sucrose.

“…The post thaw survival of porcine embryos has been investigated by several workers previously (reviewed by Nagashima et al, 1994) [8]. In these studies 1.4-1.5 M glycerol has been used exclusively as a cryoprotectant for freezing at the peri-hatching stage [4][5][6][7][12][13][14]. In the present study hatched blastocysts were also selected for freezing according to their size as the efficiency with which these can be frozen is known to decrease rapidly following hatching [4].…”