Effects Of N-acetyl-L Cysteine On Mouse Cultured Oocytes Aging In Vitro

The aging of oocytes may compromise the oocyte quality and have a profound effect on the development of early embryos and the health of the offspring.The most significant feature of aging oocytes is decreased parthenogenetic activation susceptibility,low MPF activity,cortical granule abnormalities,zona pellucida harden,poor fertilization rate,easy to cause the gene mutation,resulting in cell apoptosis or necrosis and pregnancy failure.In aging oocyte,the intracellular metabolism and mitochondrial activity were changed that some electrons were "escaped" during the process of electronic respiratory chain electron transfer,combination with other cellular material,the intracellular oxygen free radicals(ROS)were accumulated.Although ROS could be removed by glutathione normally,the level of ROS was still increased because GSH was gradually consumed during oocytes aging,which lead to cell apoptosis and decrease oocytes quality.Previous studies have shown that N-L-acetyl cysteine,as a precursor of glutathione synthesis,has antioxidant activity,which can effectively scavenge oxygen free radicals.In this experiment,mouse postovulatory oocytes were cultured in different concentration of NAC were supplement for 12 hours to discover the effect of NAC on oocyte aging delay and related molecular mechanism oocytes aging,using the fresh matured oocytes as control.A number of important indexes affecting the quality of oocytes were detected such as parthenogenetic activation rate,ROS levels,mitochondrial activity and arrangement,zona pellucida hardening degree,fertilization rate and early embryo development status,the results as follows:(1)Sensitivity of oocytes to parthenogenetic activation was significantly decreased and the MPF activity was significantly increased in aging oocytes by addition of NAC.The supplement of NAC above 2 mM(including 2 mM)had a more efficient delay effect.(2)It was found that zona pellucida hardening of aged oocytes was inhibited and also reduced the cytoplasmic fragmentation by supplement of NAC.(3)The synthesis of glutathione could be promoted by 2 mM NAC.NAC also could serve to maintain an appropriate proportion of GSH/GSSG,improve the oxidation reduction ability of oocytes and alleviate mouse aged oocytes oxidative damage by ROS.(4)The distribution and function of mitochondria in aging oocytes were improved by 2 mM NAC(5)It was postponed mouse postovulatory oocytes aging by 2 mM NAC.And NAC also could significantly improve the fertilization ability of oocytes and early embryonic development mouse aged oocytes.