5-Azacytidine induces early stage apoptosis and promotes in vitro maturation by changing chromosomal construction in murine oocytes

► 5-AzaC inhibits the condensation of chromosomes and induces chromosome instability. ► 5-AzaC induces early apoptosis and IVM in mouse oocytes. ► 5-AzaC increases the mRNA levels of caspase-3, caspase-8, caspase-9, gdf-9 and bmp-15. As an anticancer drug, 5-azacytidine (5-AzaC) has been widely used to treat various cancers. To investigate the effect of 5-AzaC on mouse oocytes cultured in vitro, we have performed morphological and molecular biology studies to examine the behavior of chromosomes and oocyte development. In 5-AzaC-treated oocytes, chromosomes were decondensed and unstable. The mRNA levels of Caspase3, Caspase8, and Caspase9 increased with the occurrence of early stage apoptosis in oocytes following 5-AzaC treatment. Furthermore, the mRNA levels of Gdf9 and Bmp15 also increased with the corresponding morphological changes in 5-AzaC-treated oocytes. In conclusion, 5-AzaC not only induced early apoptosis through both extrinsic and intrinsic pathways, but also had a positive effect on the developmental competence of mouse oocytes during in vitro maturation. These effects may be due to changes in chromosomal construction induced by DNA hypomethylation.