Effect of antifreeze protein supplementation in vitrification medium on mouse oocyte developmental competence

Objective: To investigate the effect of antifreeze protein (AFP) supplementation during mouse oocyte vitrification on the survival, fertilization and embryonic development. Design: Animal study. Setting: University laboratory. Animal(s): BDF-1 mice. Intervention(s): In vivo-matured metaphase II oocytes were vitrified with the use of CryoTop by two-step exposure to equilibrium and vitrification solution supplemented or not with 500 ng/mL AFP III. Main Outcome Measure(s): Postwarming survival, fertilization, embryonic development up to blastocyst in vitro, morphology of spindle and chromosome, membrane integrity, adenosine triphosphate (ATP) contents, and several gene expressions. Result(s): In the AFP-treated group, blastocyst formation rate was significantly higher and blastomere count with positive caspase was significantly lower compared with the nontreated group. Rate of intact spindle/chromosome, stable membrane, and ATP contents were significantly higher in AFP group. AFP group showed higher Mad2 and lower Eg5 gene expression. Both vitrification groups showed increased Hsf1, Zar1, and Zp1/Zp2 expression and decreased Hook1 and Zp3 expression compared with fresh control samples. Conclusion(s): Supplementation of AFP in vitrification medium has a protective effect on mouse oocytes for chilling injury; it can preserve spindle/membrane integrity and intracellular ATP contents. More stable spindle integrity in the AFP group may be associated with higher Mad2 and lower Eg5 gene expression. (Fertil Steril (R) 2011; 96: 1239-45. (C) 2011 by American Society for Reproductive Medicine.)