ABSTRACT
Objective: Over the last years, vitrification has been widely used for oocyte cryopreservation, in animals and humans; however, it frequently causes minor and major epigenetic modifications. The effect of oocyte vitrification on levels of acetylation of histone H4 at lysine 12 [AcH4K12], and histone acetyltransferase [Hat] expression, was previously assessed; however, little is known about the inhibition of Hat expression during oocyte vitrification. This study evaluated the effect of anacardic acid [AA] as a Hat inhibitor on vitrified mouse oocytes
Materials and Methods: In this experimental study, 248 mouse oocytes at metaphase II [MII] stage were divided in three experimental groups namely, fresh control oocytes [which were not affected by vitrification], frozen/thawed oocytes [vitrified] and frozen/thawed oocytes pre-treated with AA [treatment]. Out of 248 oocytes, 173 oocytes were selected and from them, 84 oocytes were vitrified without AA [vitrified group] and 89 oocytes were pretreated with AA, and then vitrified [treatment group]. Fresh MII mouse oocytes were used as control group. Hat expression and AcH4K12 levels were assessed by using real-time quantitative polymerase chain reaction [PCR] and immunofluoresce staining, respectively. In addition, survival rate was determined in vitrified and treatment oocytes
Results: Hat expression and AcH4K12 modification significantly increased [4.17 +/- 1.27 [P.0.001] and 97.57 +/- 6.30 [P<0.001], respectively] in oocytes that were vitrified, compared to the fresh oocytes. After treatment with AA, the Hat mRNA expression and subsequently H4K12 acetylation levels were significantly reduced [0.12 +/- 0.03 [P.0.001] and 89.79 +/- 3.20 [P.0.05], respectively] in comparison to the vitrified group. However, the survival rate was not significantly different between the vitrified [90.47%] and treatment [91.01%] groups [P>0.05]
Conclusion: The present study suggests that AA reduces vitrification risks caused by epigenetic modifications, but does not affect the quality of vitrification. In fact, AA as a Hat inhibitor was effective in reducing the acetylation levels of H4K12