The impact of vitrification on murine germinal vesicle oocyte In vitro maturation and aurora kinase A protein expression.

Purpose: Investigate the effect of vitrification on in vitro maturation (IVM) and expression of Aurora kinases A, B, and C in germinal vesicle (GV)-stage oocytes.

Methods: GV-stage oocytes from B6D2F1 female mice 7-11 weeks of age were vitrified after collection, thawed, and matured in vitro for 0, 4, 8, and 12 h (hrs). The rate of germinal vesicle breakdown (GVBD), spindle apparatus assembly, and Aurora kinase mRNA and protein expression during IVM was measured.

Results: Oocyte vitrification was associated with significant delays in both GVBD and normal spindle apparatus assembly at 4 and 8 h of IVM (p < 0.05). There was no difference in mRNA levels between control and vitrified oocytes for any of the Aurora kinases. Aurora A protein levels were reduced in vitrified compared to control oocytes at 0 h (p = 0.008), and there was no difference at 4 and 8 h (p = 0.08 and 0.69, respectively) of IVM.

Conclusions: Vitrified oocytes have delayed GVBD and normal spindle assembly during in vitro maturation. Reduced levels of Aurora A protein immediately post-thaw may be associated with the impaired oocyte maturation manifested by the delayed progression through meiosis I and II, and the atypical timing of the formation of meiotic spindles in vitrified GV-stage oocytes.