Effect of different penetrating and non-penetrating cryoprotectants and media temperature on the cryosurvival of vitrified in vitro produced porcine blastocysts.

The aim of this study was to determine the most efficient vitrification protocol for the cryopreservation of day 7 in vitro produced (IVP) porcine blastocysts. The post-warm survival rate of blastocysts vitrified in control (17% dimethyl sulfoxide + 17% ethylene glycol [EG] + 0.4 mol/L sucrose) and commercial media did not differ, nor did the post-warm survival rate of blastocysts vitrified in medium containing 1,2-propandiol in place of EG. However, vitrifying embryos in EG alone decreased the cryosurvival rate (55.6% and 33.6%, respectively, p < .05). Furthermore, the post-warm survival rates of blastocysts vitrified with either trehalose or sucrose as the non-penetrating cryoprotectant did not differ. There was also no significant difference in post-warm survival of blastocysts vitrified in control (38°C) media and room temperature (22°C) media with extended equilibration times, although when blastocysts were vitrified using control media at room temperature, the post-warm survival rate increased (56.8%, 57.3%, 72.5%, respectively, p < .05). The findings show that most cryoprotectant combinations examined proved equally effective at supporting the post-warm survival of IVP porcine blastocysts. The improved post-warm survival rate of blastocysts vitrified using media held at room temperature suggests that the cryoprotectant toxicity exerted in 22°C media was reduced.

A comparison of different vitrification devices and the effect of blastocoele collapse on the cryosurvival of in vitro produced porcine embryos.

The aim of this study was to determine the optimum conditions for vitrifying in vitro produced day 7 porcine embryos using different vitrification devices and blastocoele collapse methods. Firstly embryos were collapsed by micro-pipetting, needle puncture and sucrose with and without conducting vitrification. In the next experiment, non-collapsed embryos were vitrified in an open device using either superfine open-pulled straws (SOPS) or the CryoLoop(TM) system, or vitrified in a closed device using either the CryoTip(TM) or Cryo Bio(TM)'s high security vitrification system (HSV). The post-thaw survival of embryos vitrified in the open devices did not differ significantly (SOPS: 37.3%; CryoLoop(TM): 37.3%) nor did the post-thaw survival of embryos vitrified in the closed devices (CryoTip™: 38.5%; HSV: 42.5%). The re-expansion rate of embryos that were collapsed via micro-pipetting (76.0%) did not differ from those that were punctured (75.0%) or collapsed via sucrose (79.6%) when vitrification was not performed. However, embryos collapsed via sucrose solutions (24.5%) and needle puncture (16.0%) prior to vitrification were significantly less likely to survive vitrification than the control (non-collapsed) embryos (53.6%, P < 0.05). The findings show that both open and closed vitrification devices were equally effective for the vitrification of porcine blastocysts. Collapsing blastocysts prior to vitrification did not improve survival, which is inconsistent with the findings of studies in other species. This may be due to the extremely sensitive nature of porcine embryos, and/or the invasiveness of the collapsing procedures.