Abstract
Background:
As the porcine oocyte is the most sensitive to low temperature damage, it has been difficult to cryopreserve compared to those from other domestic animals. However, at present, vitrification is used as a method for the cryopreservation of both oocytes and embryos in this species.
Aim:
Our aim was to analyze alterations in metabolic parameters in vitrified-warmed in vitro matured porcine oocytes at different post-warming recuperation times. Additionally, metaphase II plate recovery time analysis, in vitro fertilization and intracytoplasmic sperm injection were carried out to evaluate oocyte recovery capacity.
Methods:
Oocytes were vitrified-warmed and then incubated for 0, 3 or 21h post-warming to assess biochemical parameters.
Results:
Oocyte viability and morphology were not affected by vitrification-warming. Cytosolic oxidative status, active mitochondria and reactive oxygen species levels presented changes at the different time points in control and vitrified-warmed oocytes (P<0.05) as well as differences between both groups (P<0.05). NAD(P)H levels remained constant throughout different recuperation times, but were significantly lower in vitrified-warmed oocytes (P<0.05). Metaphase II plate recovery occurred mostly between 3 and 4h post-warming, but the percentage of metaphase II was reduced by vitrification-warming. Sperm head decondensation and pronuclear formation capacities were not modified.
Conclusion:
In conclusion, vitrification-warming generates biochemical alterations in porcine oocytes that would be, in part, responsible for affecting their performance. So, although the technique is a valid alternative for porcine oocyte cryopreservation, the protocols should be adapted to minimize those alterations.

Key words: Cryopreservation, Mitochondria, Porcine oocytes, Reactive oxygen species, Vitrification