Biochemical Variations in Vitrified-warmed in Vitro Matured Porcine Oocytes

Abstract

Abstract 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. Our aim was to analyze biochemical variations in vitrified-warmed in vitro matured porcine oocytes at different recovery times using a minimum volume vitrification system. Additionally, metaphase II plate recovery time analysis, in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) were carried out to evaluate oocyte maturational capacity recovery. Oocytes were vitrified-warmed and then incubated for 0h, 3h or 21h post-warming to assess biochemical parameters. Oocyte viability or morphology were not affected by vitrification-warming. Cytosolic oxidative status, active mitochondria and reactive oxygen species levels presented variations at the different time points in both control and vitrified-warmed oocytes (P < 0.05) as well as differences between one group and the other (P < 0.05). NAD(P)H levels remained constant throughout different recovery 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 process. Sperm head decondensation and pronuclear formation capacities were not modified. In conclusion, vitrification-warming generates biochemical modifications in porcine oocytes that would be in part responsible for affecting their performance. So, although the technique is a possible alternative for porcine oocyte cryopreservation, improvements in the vitrification-warming protocols should be included to minimize the metabolic variations produced during this process.