Viability of porcine embryos after vitrification using water-soluble pullulan films

The efficiency of a porcine embryo vitrification method that uses water-soluble films of pullulan, a naturally-occurring polysaccharide polymer, was compared with two other types of vitrification methods using different devices and solutions for vitrification and warming. Blastocysts collected in vivo and vitrified by the conventional straw (ST), Cryotop((R)) (MVC) or pullulan film vitrification (PFV) methods were stored in liquid nitrogen for a certain period of time, after which the cryoprotective agents were removed by stepwise dilution. Fresh embryos were used as controls for the non-vitrification group. The vitrified-warmed embryos were incubated in TCM199 with 0.1 mM beta-mercaptoethanol and 20% fetal bovine serum for 24 h at 38.5 C in humidified air with 5% CO(2) to evaluate their viability. The survival rate of embryos in the ST group (48.3%) was significantly lower than that of those in the MVC (70.7%), PFV (79.0%) and non-vitrification (94.4%) groups. The oxygen consumption rate after vitrification was significantly lower than that before vitrification in the ST group, but was not significantly different in the MVC and PFV groups. Both the oxygen consumption rates of embryos after warming and the live cell numbers in the ST group were lower than those in the MVC group, while they did not differ significantly between the PFV and MVC groups. There was a correlation between the oxygen consumption rate and the number of live cells in vitrified embryos after warming. Our results demonstrated that in vivo-derived porcine embryos could be vitrified using pullulan films.